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If there’s no controversy over evolution, what’s this?

Science (17 February 2006) has an article on the other selection — Darwin had identified not only natural selection but also sexual selection. According to the authors of this article, sexual selection needs to be dropped and replaced with a theory of cooperative games. Especially striking in the article is the statement “problems with this narrative have continued to accumulate” and reference to “Darwin’s central narrative.” Narrative indeed. Ordinarily, the study of narrative belongs under lit-crit. It’s finally clear why ID isn’t welcome among evolutionary biologists: the study of narratives provides no clue to the engineering problems that biological systems pose. Of course, it goes without saying that this article provides absolutely no justification for thinking that there is a controversy surrounding evolution — it merely suggests that one of Darwin’s two greatest contributions to evolutionary theory was completely out to lunch.

Reproductive Social Behavior: Cooperative Games to Replace Sexual Selection
Joan Roughgarden,1* Meeko Oishi,2 Erol Akçay1

Theories about sexual selection can be traced back to Darwin in 1871. He proposed that males fertilize as many females as possible with inexpensive sperm, whereas females, with a limited supply of large eggs, select the genetically highest quality males to endow their offspring with superior capabilities. Since its proposal, problems with this narrative have continued to accumulate, and it is our view that sexual selection theory needs to be replaced. We suggest an approach that relies on the exchange of direct ecological benefits among cooperating animals without reference to genetic benefits. This approach can be expressed mathematically in a branch of game theory that pertains to bargaining and side payments.

1 Department of Biological Sciences, Stanford University, Stanford, CA 94305-5020, USA.
2 Sandia National Laboratory, Post Office Box 5800, Albuquerque, NM 87185-1137, USA.
* To whom correspondence should be addressed. E-mail: [email protected]

A recent review of diversity in animal reproductive social behavior (1) raises questions about Darwin’s 1871 theory of sexual selection (2). Unlike the theories of evolution through common descent and of evolutionary change by natural selection, Darwin’s theory of sexual selection has continually drawn criticism from evolutionists, notably Huxley in 1938 (3). Darwin wrote “Males of almost all animals have stronger passions than females” and “the female… with the rarest of exceptions is less eager than the male… she is coy.” Darwin explained these templates as resulting from females choosing mates who are “vigorous and well-armed… just as man can improve the breed of his game-cocks by the selection of those birds which are victorious in the cock-pit.” He continues, “Many female progenitors of the peacock must… have… by the continued preference of the most beautiful males, rendered the peacock the most splendid of living birds.”

Since 1871, sexual selection theory has often been restated (4), yet contemporary definitions share Darwin’s central narrative: “We now understand… Males, who can produce many offspring with only minimal investment, spread their genes most effectively by mating promiscuously… Female reproductive output is far more constrained by the metabolic costs of producing eggs or offspring, and thus a female’s interests are served more by mate quality than by mate quantity” (5). This narrative is taught in biology textbooks (6), is axiomatic to evolutionary psychology (7), and is broadcast in popular media (8).

The reproductive social behavior of most species has not been studied, but a great many of those that have been do not conform to Darwinian sexual-selection templates. We suggest that sexual selection is always mistaken, even where gender roles superficially match the Darwinian templates.

There are fundamental problems that universally undercut all applications of sexual selection theory to any species, including the contradiction between sexual selection’s rationale and the reason for sexual versus asexual reproduction, the difficulty of sustaining a stable hierarchy of genetic quality within a gene pool in the face of continued directional selection for high-ranked genotypes, and the use of different fitness definitions for males and females. These and other fatal problems are detailed in the references accompanying table S1.

We think that the notion of females choosing the genetically best males is mistaken. Studies repeatedly show that females exert choice to increase number, not genetic quality, of offspring and not to express an arbitrary feminine aesthetic. Instead, we suggest that animals cooperate to rear the largest number of offspring possible, because offspring are investments held in common. We therefore propose replacing sexual selection theory with an approach to explaining reproductive social behavior that has its basis in cooperative game theory. We introduce a notion of allocating time into various relationships to maximize cooperative, or “team,” fitness. In this theory, we can observe that diverse social organizations emerge from how individuals accrue direct benefits from the relationships they develop with one another within diverse ecological contexts.

Cooperative Games in Reproductive Social Behavior
Here, we explain reproductive social behavior in developmental time, not evolutionary time. A social system develops from the interaction of individuals just as body parts develop from the interaction of tissues. In our model, each animal acts continually as an individual or as a team member, and the value of an action is scored by how it contributes to that animal’s average fitness accumulation rate (9). An individual’s actions involve obtaining and exchanging direct benefits to increase the number of offspring successfully reared (10-14). We further envision a future two-tier theory that will embed this phenotypic treatment within an overarching evolutionary-genetic model.

Maynard Smith introduced game theory to biology in the 1980s, including the evolutionary stable strategy (ESS), a population-genetic counterpart to the Nash competitive equilibrium (NCE) of game theory (15). A competitive game ends when an NCE is attained, i.e., the state where each player cannot better its position, given the positions of the other players. In competitive games, the players do not communicate.

In cooperative games, players make threats, promises, and side payments to each other; play together as teams; and form and dissolve coalitions. Cooperative games usually end up at different solutions to an NCE. Nash also investigated cooperative games and introduced the concept of a Nash bargaining solution (NBS) as an outcome of these games (16) . . .

Social note: Joan Roughgarden used to be Jonathan Roughgarden prior to a sex change operation, http://joandistrict6.com/nature-profile.html, and has been trying to discredit sexual difference for many years. Well, at least here’s one critic of Darwinism who isn’t a Christian fundamentalist.

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57 Responses to If there’s no controversy over evolution, what’s this?

  1. What do you know, a mathematical solution to an evolutionary biology phenomena. Who would have thought.

    I’ve always sensed an inherent contradiction with sexual selection. The logic goes like this: why does a peacock have such highly colorful tail-feathers? Because the female peacocks choose them? Then why do the female peacocks choose them? Because they’re highly colorful.

    Does anyone detect a circular argument here?

  2. PaV-

    The problem is thats not what is actualy said. The female preference for the coloration exists because those females that had that preference selected higher quality mates. The coloration is very costly, and vividness and complextiy of design is proportional to more then one quality measurment of the phenotype. I dont see anything circular in this.

  3. Populations never had anything to do with creative evolution. Like every other genetic change the changes that produced evolutionary progress occurred in the germinal line of individual organisms. To assume otherwise is pure mysticism, something Darwinians are very good at. Apparently such organisms are no longer with us. Phylogeny, like ontogeny, has also proven to be predetermined, self regulated and self terminated with inevitable extinction the counterpart to the death of the individual.

    Ask not for whom the bell tolls. It tolls for all of us.

  4. Hmm. That’s a pretty disturbing picture. How does it apply to the post?

  5. Forgive my denseness, but why does pointing a gun in my face constitute “terms that I’ll understand”?

    Along these lines, I’m growing increasingly concerned about the stuff that gets posted here: this, referring to the ACLU as “terrorists,” or complaining about the rules employed by the Panda’s Thumb webmaster. If they fix the trackbacks to your satisfaction, is that going to advance the cause of ID? Is this the kind of stuff I need to know about if I’m to understand ID? -sb

  6. Trent said: “The female preference for the coloration exists because those females that had that preference selected higher quality mates. . . . “I dont see anything circular in this.”

    Here’s where the circularity comes in: highly-colored tail-feathers will not evolve until a sexual preference for them evolves. A sexual preference for highly-colored tail-feathers will not evolve until highly-colored tail-feathers evolve. Which came first: the feathers or the preference?

  7. Does anyone else notice that more & more Darwinian explanations are sounding a lot like mythology? The just so stories are amazingly similar to the accounts of nature attributed to the pantheistic gods of the Greeks & Romans.

    Just wondering.

  8. Hi Pav,

    Your question on circularity is quite valid, however, I’d suggest that it’s not a binary thing. (colored vs. non-colored) The scenario would depend on variation by degrees.
    For example, red hair in humans didn’t just pop up red one day. Across the globe, I’m sure you could line up a thousand people that have brown hair varying in increasing degrees to bright orange hair. Each person side by side would have little to no variation between hair color, yet the two extreme ends would look significantly different.
    My personal opinion is that genetic drift would account for getting you enough red hair coloring for people to notice, and have a sexual preference for (reddish hair) Generations of sexual preference could possibly push it to the extreme where you have blazing red hair. So in the case of your circularity question, I’d guess that the color came first, but only in a much slighter degree.

    (i’m using red hair as an example of degrees, not sexual selection. We all know that blondes get the upper hand in that. J/K :)

  9. What is the selection pressure exerted upon the females to make them prefer the coloration?
    Is there supposed to be some correlation between being attracted to the coloration and having more progeny?

  10. Oh my gosh, I think I’m going to burst out laughing again!!!

    SteveB wrote:
    Along these lines, I’m growing increasingly concerned about the stuff that gets posted here: this, referring to the ACLU as “terrorists,” or complaining about the rules employed by the Panda’s Thumb webmaster. If they fix the trackbacks to your satisfaction, is that going to advance the cause of ID? Is this the kind of stuff I need to know about if I’m to understand ID? -sb
    ….
    Steve, here’s all you have to know about this site:
    There IS a moderator and you’re not him.

    Next!

  11. Red Reader,

    Thank you for the clarification. It is interesting that with all the criticism of Ohio’s decision to now allow critical analysis (of evolution), you have responded to my critical but honest question with the “You’re not the moderator” mantra. Hmmm… I also understand that the moderator has the right to post–or delete–what he wants. It’s his ballpark, he can pitch however he wants to.

    My assumption was that peoople include pictures to illustrate or clarify a point. His apparent intention was to communicate something in “terms I could understand.” Since I didn’t understand I asked. I didn’t rant. Didn’t call anyone names. I asked a question.

    So was there a point to the picture? Does it illustrate something about darwinian sexual selection?

  12. PaV asks:
    “Here’s where the circularity comes in: highly-colored tail-feathers will not evolve until a sexual preference for them evolves. A sexual preference for highly-colored tail-feathers will not evolve until highly-colored tail-feathers evolve. Which came first: the feathers or the preference?”

    R.A. Fisher would say the feathers came first. Here’s how it would play out, according to his theory:

    1. You have a population of birds with quite ordinary plumage.

    2. The healthiest birds, as a byproduct of their health, produce more or brighter feathers.

    3. Females who happen to prefer males with more/brighter plumage are reproductively more successful, because their offspring benefit from the genes of their healthy fathers.

    4. The preference for more/brighter feathers becomes widespread among the females of the population.

    Now you have the conditions for a classic positive feedback loop:

    5. Since the females prefer males with more/brighter plumage, it “pays” the males to evolve in that direction.

    6. For the female to propagate her genes, she needs to ensure that her offspring will be able to attract mates. In the case of her male offspring, that means they need showier plumage than the competition. Breeding with a showier male means that her male offspring will also have showier plumage and thus be able to attract females.

    Steps 5 and 6 constitute the feedback loop.

    Why doesn’t it go on forever? Because there is a cost to maintaining showy plumage:

    a) showy plumage attracts the attention of predators as well as mates.

    b) showy plumage is heavy to carry around and slows the bird down.

    c) there is a high energy cost to producing showy plumage.

    Fisher argued that the positive feedback loop of sexual selection would continue to exaggerate the selected trait until the costs balanced the benefits.

    As you can see, this is not circular reasoning, because the whole process begins with the healthier males producing healthier-looking plumage. At that time the females have not yet evolved a preference for showier males.

  13. Dr. Dembski wrote:
    “Especially striking…is the statement “problems with this narrative have continued to accumulate” and reference to “Darwin’s central narrative.” Narrative indeed….It’s finally clear why ID isn’t welcome….: the study of narratives provides no clue to the engineering problems that biological systems pose.”

    (Sidenote: edit “problems with the narrative” to read “problems with the ‘just so’ story”.)

    Like modern NeoDarwinists, ancient Ptolemaic astronomy had a problem with its “narrative” as well, but in the end, retrogressive motions of planetary orbits were no barrier to the creative ingenuity of its defenders.

    The study of astronomy became NOT the study of the motions of planets, but the study of Ptolemy’s *theory* of the motions or the planets: problems with the theory didn’t invalidate the theory, problems merely called for further refinements of the theory.

    Another similarity: Budding scientists not only had to understand Ptolemy’s theory, they had to *believe* Ptolemy’s theory. Dissenters were called “heretics” and treated as such.

    See “Ptolemaic astronomy” at http://en.wikipedia.org/wiki/Ptolemaic_system

    Another interesting similarity to the present context:
    “A dissenter named Copernicus worked as a *church canon*, governor, *administrator*, *mathematician*, economist, jurist, physician and astrologer…. His formulation of how the Sun rather than the Earth is at the center of the universe…came to mark the starting point of modern astronomy…encouraging young astronomers, scientists and scholars to TAKE A MORE SKEPTICAL ATTITUDE TOWARD ESTABLISHED DOGMA.” ( http://en.wikipedia.org/wiki/Copernican_system )

  14. For what it’s worth, I think the preference came first, because it is widely dispersed across many species. Since males compete, females get to choose, and the males of many species are prettier – look at guppies.

  15. Valerie: I’ll intersperse my remarks.

    R.A. Fisher would say the feathers came first. Here’s how it would play out, according to his theory:

    Sir Fred Hoyle, the famous astrophysicist, wrote a book about the “Mathematics of Evolution”. He did not have kind things to say about Fisher’s theory. He more or less debunks it. But, let’s continue….

    1. You have a population of birds with quite ordinary plumage.

    So far, so good.

    2. The healthiest birds, as a byproduct of their health, produce more or brighter feathers.

    Are we assuming this? Is there some basis for assuming this? Do healthy cats have nicer fur?

    3. Females who happen to prefer males with more/brighter plumage are reproductively more successful, because their offspring benefit from the genes of their healthy fathers.

    Is there any basis to this assumption? What about the simple vagaries of life? Predation is more-or-less random; whether or not there is an abundant food-supply is a simple matter of chance. And healthy parents don’t necessarily produce healthy off-spring. So, “on average”, I would think all this gets cancelled out. So I don’t know why we’re entitled to make this assumption.

    4. The preference for more/brighter feathers becomes widespread among the females of the population.

    What is the ‘selective pressure’ that brings this about? To be a little reckless, do the mother hens get together and talk about who had the healthiest babies, and then figure out that ‘healthy’ daddies are the trick?

    Now you have the conditions for a classic positive feedback loop:

    Only hypothetically. We’re assuming all sorts of things that we don’t know are true.

    5. Since the females prefer males with more/brighter plumage, it “pays” the males to evolve in that direction.

    It doesn’t pay them at all. They’re still going to die. And if they have more little chicks, then there’s only more mouths to feed and every prospect that they will have to go hungry feeding the little ones. And how do they “evolve” in that direction? I thought evolution was undirected. So we have to assume that the mutant genes are dominant (quite rare), have directionality (contrary to theory) and, according to Fisher’s still controversial mathematics, they have to become “fixed”. Are we now in scientific jello? What backs up all these assumptions piled up on one another?

    6. For the female to propagate her genes, she needs to ensure that her offspring will be able to attract mates. In the case of her male offspring, that means they need showier plumage than the competition. Breeding with a showier male means that her male offspring will also have showier plumage and thus be able to attract females.

    These must be some really smart females to have figured all this out by themselves. You’re talking about animals acting with purpose. Is this really believable?

    Steps 5 and 6 constitute the feedback loop. . . .

    Fisher argued that the positive feedback loop of sexual selection would continue to exaggerate the selected trait until the costs balanced the benefits.

    Again, his mathematics, and his assumptions, are (1) suspect, and (2)ASSUMPTIONS–how do we know that they’re true?

    As you can see, this is not circular reasoning, because the whole process begins with the healthier males producing healthier-looking plumage. At that time the females have not yet evolved a preference for showier males.

    The argument is nuanced; but fallacious. You have no way of proving any of the steps. You called it a “feedback loop”. Doesn’t that sound “circular”?

  16. 1-6
    Ah, just so.

  17. Does this mean little boys and girls will be born with tattoos and body piercings soon? Oh joy. I can hardly wait.

  18. “…what I find intriguing is that Darwinists are not troubled by the unfitness of the peahen’s sexual taste. Why would natural selection, which supposedly formed all birds from lowly predecessors, produce a species whose females lust for males with life-threatening decorations? The peahen ought to have developed a preference for males with sharp talons or mighty wings. I don’t know what creation-scientists might suppose, but it seems to me that the peacock and peahen are just the kind of creatures a whimsical Creator might favor, but that an ‘uncaring mechanical process’ like natural selection would never permit to develop.” Philip Johnson, Darwin on Trial, pp. 30-31.

  19. Sorry: Phillip not Philip

  20. Hi PaV,

    Some responses to your comments:

    You wrote:
    “Are we assuming this [that healthy birds produce more or brighter plumage than unhealthy ones]? Is there some basis for assuming this? Do healthy cats have nicer fur?”

    From http://www.peafowl.org:
    “After the peacock is five or six years old, the tail train will remain consistent in length and quality for the rest of the bird’s life as long as the bird remains healthy.”

    And yes, healthy cats do have nicer fur (fuller and shinier).

    I wrote:
    “Females who happen to prefer males with more/brighter plumage are reproductively more successful, because their offspring benefit from the genes of their healthy fathers.”

    You wrote:
    “Is there any basis to this assumption? What about the simple vagaries of life? Predation is more-or-less random; whether or not there is an abundant food-supply is a simple matter of chance. And healthy parents don’t necessarily produce healthy off-spring. So, “on average”, I would think all this gets cancelled out. So I don’t know why we’re entitled to make this assumption.”

    For natural selection to work, all that’s required is that some variants be more likely to survive than others. Even a tiny advantage will cause a variant to dominate the population over time.

    Predation is *not* random. Individuals who are more vigilant or faster at fleeing will survive more often than their slower, less alert counterparts. And in times of food scarcity, variations can make all the difference for survival (witness Peter and Rosemary Grant’s work with finch beak sizes in the Galapagos). And sure, healthy parents don’t always produce healthy offspring, but they are more likely to do so than unhealthy parents, which is all that natural selection needs to operate.

    I wrote:
    “The preference for more/brighter feathers becomes widespread among the females of the population.”

    You wrote:
    “What is the ’selective pressure’ that brings this about? To be a little reckless, do the mother hens get together and talk about who had the healthiest babies, and then figure out that ‘healthy’ daddies are the trick?”

    No. Sexual attraction is largely instinctual (even in humans). The females who happen to be attracted to healthy males (based on plumage) tend to get more descendants into future generations than the ones who are attracted to unhealthy males. Over time, this means that females who prefer healthy plumage come to dominate the population.

    I wrote:
    “Since the females prefer males with more/brighter plumage, it “pays” the males to evolve in that direction.”

    “It doesn’t pay them at all. They’re still going to die.”

    It pays them in the sense that they get their genes into future generations if their plumage is sufficiently attractive to females.

    “And if they have more little chicks, then there’s only more mouths to feed and every prospect that they will have to go hungry feeding the little ones.”

    Peafowl don’t feed their young. The chicks are capable of foraging on their own.
    And anyway, there are adaptations which deal with food scarcity. Some birds will forego breeding in times of food scarcity. Others will reduce the brood size by allowing the youngest chick (or chicks) to starve, thus improving the odds that the older chicks will survive.

    “And how do they “evolve” in that direction? I thought evolution was undirected.”

    It *is* undirected, as far as we can tell. Being undirected is not the same as being directionless, however. Natural selection definitely “prefers” some variants over others. The direction is provided by the environment.

    “So we have to assume that the mutant genes are dominant (quite rare), have directionality (contrary to theory) and, according to Fisher’s still controversial mathematics, they have to become “fixed”. Are we now in scientific jello? What backs up all these assumptions piled up on one another?”

    Dominance vs. recessiveness is a continuum, not a dichotomy. A more recessive allele takes longer to become fixed than a more dominant allele, all else being equal.

    I wrote:
    “For the female to propagate her genes, she needs to ensure that her offspring will be able to attract mates. In the case of her male offspring, that means they need showier plumage than the competition. Breeding with a showier male means that her male offspring will also have showier plumage and thus be able to attract females.”

    You wrote:
    “These must be some really smart females to have figured all this out by themselves. You’re talking about animals acting with purpose. Is this really believable?”

    Intelligence is not necessary. Instinct is enough. (Having said that, many animals do appear to act with conscious purpose. Even crows have been observed in the lab bending a wire to form a hook for retrieving food. See this great video (scroll down; it’s on the left side of the page).

    http://users.ox.ac.uk/~kgroup/.....main.shtml

    You wrote:
    “You called it a “feedback loop”. Doesn’t that sound “circular”?”

    The loop is circular, but the reasoning behind it is not. Circuit designers use positive feedback loops all the time to produce working oscillators. Are you telling me that they’re deluded in doing so?

    Your objection makes as much sense as saying that all geometric proofs involving circles are examples of “circular reasoning”.

    Even a tiny advantage will cause a variant to dominate the population over time.

    Absolutely not true. The environment is far too unpredictable. The fastest antelope is usually the first one to break a leg in a hidden ditch when the herd is in paniced flight from a predator. Survival of the fittest is a stupid tautology better stated as survival of the survivors. It’s really survival of the luckiest. The antelope lucky enough to be in the middle of the herd at the time of attack is the one with the best chance of survival. -ds

  21. Charlie, j:

    Rather than being a just-so story, the theory of sexual selection makes testable predictions. For example, sexual selection theory says that the choosier sex should be the sex which invests the most in the offspring. Females generally produce a few large eggs, while males produce many small sperm. On top of that, females tend to invest more time and energy after birth as well. So sexual selection theory predicts that females will generally be the choosy sex, and they are.

    SS theory also says that the non-choosy sex will be the one which develops the “showy” characteristics. Again, SS theory is confirmed by the fact that males tend to be showier than the females.

    Finally, SS theory predicts that in cases where the *males* actually invest more in the offspring than the females, *they* should be the choosy ones and the females should be the showier ones.

    This is borne out as well. For example, male phalaropes care for their offspring before and after hatching. The female phalaropes are the brightly colored ones, and they actively court the choosy males, just as SS theory predicts.

    Far from being oddities designed by a whimsical Creator, as Johnson proposes, they actually follow a quite regular pattern which is predicted by evolution.

    If the Creator is whimsical, why didn’t he create both peacocks and peahens with garish tails? Why didn’t he make some of the females showier even though they invest more in the offspring? Why did he follow these strange rules that match so well with evolutionary theory?

  22. Valerie,

    I know you are already answering a number of people on this thread, and I don’t want to pile on. But if you have the time, I’m puzzled about the linking of “health” and “bright plumage” in peacocks.

    Health is typically indicated by a normal range that includes both a maximum and minimum. Rosy cheeks are an indication of health in children, and both pale and excessively bright red cheeks indicate ill health, one by defect and the other by excess. I can see how dull, sparse fur would indicate ill health in a cat because full, shiny fur is the norm for healthy cats. But the evolutionary argument is that a peacock born with excessivley bright plumage was also the healthiest peacock. In other words, it goes against our common experience that health resides in a mean, and that both the excessive and defective conditions are unhealthy.

    Now our common experience is not definitive and it is possible that a peacock was once born with unprecedentedly bright plumage who was also unprecedentedly healthy. But to show that this is more than speculation against common experience, I think we need to at least show that the relationship between peacock plumage brightness and health does not reside in a mean. That is, the peacocks with the absolutely brightest plumage are also the absolutely healthiest. If that is the case, then it is certainly reasonable to conclude that peacock plumage will get brighter with every generation. I surfed around http://www.peafowl.org, and I couldn’t find any indication that birds with tails that are excessively colored and ornamented are also excessively healthy. The only article I found about an unusual tail indicated that the unusual tail did not impair the health of the bird. It seems like peacock tails are like most other biological structures, with health that resides in a mean rather than an extreme.

    Cheers,
    Dave T.

  23. Valerie:
    You wrote:
    From http://www.peafowl.org:
    “After the peacock is five or six years old, the tail train will remain consistent in length and quality for the rest of the bird’s life as long as the bird remains healthy.”
    And yes, healthy cats do have nicer fur (fuller and shinier).
    Seems to me that cats mate at night. Can you make out that difference at night? More seriously, has any experiment been done to prove that this kind of selection actually takes place?

    You wrote: “For natural selection to work, all that’s required is that some variants be more likely to survive than others. Even a tiny advantage will cause a variant to dominate the population over time.
    Predation is *not* random. Individuals who are more vigilant or faster at fleeing will survive more often than their slower, less alert counterpart. And in times of food scarcity, variations can make all the difference for survival (witness Peter and Rosemary Grant’s work with finch beak sizes in the Galapagos). And sure, healthy parents don’t always produce healthy offspring, but they are more likely to do so than unhealthy parents, which is all that natural selection needs to operate.”

    This is simply assumed, not demonstrated. And in the case of the finches, the beak sizes arose quickly and then went back to their original size when the weather changed back. This is no more than adaptation. You know, there’s genetic load calculations that you can do. To have some trait that evolves work itself through a population requires a huge amount of finches dying. That many finches couldn’t have died in that short of a time without the entire population nearly dying off at one point. That’s not what’s observed. It is entirely more feasible to assume that the birds simply adapt their beak size to the current conditions. You can’t account for this using the mathematics of the Modern Synthesis.

    You wrote:
    “The preference for more/brighter feathers becomes widespread among the females of the population.”
    I wrote:
    “What is the ’selective pressure’ that brings this about? To be a little reckless, do the mother hens get together and talk about who had the healthiest babies, and then figure out that ‘healthy’ daddies are the trick?”
    You wrote: “No. Sexual attraction is largely instinctual (even in humans). The females who happen to be attracted to healthy males (based on plumage) tend to get more descendants into future generations than the ones who are attracted to unhealthy males. Over time, this means that females who prefer healthy plumage come to dominate the population.”
    You’re simply presuming that the females that “happen to be attracted to healthy males … tend to get more descendants”. Has that ever been tested and proven? And why go by tail-feathers? Why not make sticking out your tongue part of the mating ritual? Wouldn’t that make more sense?
    You wrote: “It pays them in the sense that they get their genes into future generations if their plumage is sufficiently attractive to females.”
    You make it sound like a “Far Side” cartoon. The peacocks are huddled around the local tavern’s bar. One peacock says to the other, “Yeah, Sarah’s really been eyeing my feathers. You know, I think that one’s going to bring me a lot of great-great grandchildren.” Peacocks can’t think like we do. They simply live and die. They don’t worry about ‘posterity’; only humans do that.

    You wrote: “Peafowl don’t feed their young. The chicks are capable of foraging on their own.
    And anyway, there are adaptations which deal with food scarcity. Some birds will forego breeding in times of food scarcity. Others will reduce the brood size by allowing the youngest chick (or chicks) to starve, thus improving the odds that the older chicks will survive.”
    You wrote this in response to my reply saying that it isn’t an advantage to the peacocks to have more young. But you seem to undermine your whole argument here. I don’t know if you noticed that. You’ve been arguing that NS is bring about all these changes because of variable rates of generation due to the “healthy” (colored tails) males. And you say that even the tiniest of advantages will spread. And here you’re admitting that some birds don’t even breed when food is scarce, or that they might reduce their brood size. This sounds like a much more important determinant of “great-great-grandchildren” than colored tail-feathers. I think that’s fairly clear, right?

    You wrote: “It *is* undirected, as far as we can tell. Being undirected is not the same as being directionless, however. Natural selection definitely “prefers” some variants over others. The direction is provided by the environment. “
    You have to admit that this sure sounds like you’re saying: “Natural selection directs things along in an undirected way.” And that sort of statement, as they say, doesn’t add up, I’m afraid.

    You wrote: “For the female to propagate her genes, she needs to ensure that her offspring will be able to attract mates…..”

    I question this. You responded:

    “Intelligence is not necessary. Instinct is enough.”

    So females have an instinct to propagate her genes. Do birds know what genes are? I know that sounds facetious, silly; but, the reality is that birds have an instinct to breed—no one would deny that; yet, to say that she wants to ‘ensure that her offspring will be able to attract mates…’, well, that sounds way too anthropomorphic to pass as science for me.

    You wrote: “Your objection makes as much sense as saying that all geometric proofs involving circles are examples of ‘circular reasoning’.”
    I sort of had my tongue in my cheek when I was talking about the “feedback loop.”

    Valerie:

    I see no doubt,as you present the argument, that this is circular reasoning. Circular reasoning involves assuming as a premise part, or all, of what you propose to demonstrate.
    Now, in this case, what is to be demonstrated?

    Answer: that the colored tails of peacocks are the direct result of sexual selection.

    Sexual selection is selection based on the preferences of the male/female of the species for particular sexual traits in the other sex. So, we must demonstrate/prove that the colored tails of peacocks are the direct result of peahens preferring them.

    The argument goes something like this:

    A.) Some peacocks developed colored tail-feathers.
    B.) Peahens preferred the colored tail-feathers.
    C.) As a result, all peacocks have colored tail-feathers.

    CONCLUSION: Therefore, it’s clear that the colored tail-feathers of the peacock is the direct result of the peahens preferring them.

    Now, is proposition B true or false? How do we prove it one way or another? Darwinism says that the proof that B is true is that peacocks have colored tail-feathers. So, to prove that the colored plumage of peacocks is due to ‘selection’, we have to assume that the ‘selection’ of colored plumage (i.e., peahens prefer colored tail-feathers: proposition B) has already taken place. So you’re trying to ‘prove’ that which you have already ‘assumed.’ Thus, a circular argument.

    Valerie:

    In your response to Charlie J., you said that “SS theory also says that the non-choosy sex will be the one which develops the “showy” characteristics. Again, SS theory is confirmed by the fact that males tend to be showier than the females.”

    This is ‘loopy’ again. If animals produce sexually, and one sex is ‘showy’, the other sex is, of course, going to be the ‘choosy’ one. What other options are there? Is the one sex going to mate with itself? So in what way is this a ‘prediction’? It’s a tautology again.

  24. Valerie,

    I think it is a stretch for SS theory to take credit for “predicting” something which is really inevitable, i.e., that the non-choosy sex will be showier. It’s like saying competitors compete.

    “If the Creator is whimsical, why didn’t he create both peacocks and peahens with garish tails? Why didn’t he make some of the females showier even though they invest more in the offspring? Why did he follow these strange rules that match so well with evolutionary theory?”

    The rules are not strange at all. Animals have sex according to the best reproductive schedule for their species. This centers generally upon the female. Since the essential (often only) male role is impregnation, it is imperative that he be duped into feeling sex is a paramount good, and it would be absurd for him to be moody about it.

    Even if the whimsical creator had made them the same, they would not have stayed that way. The peahens would have dropped the characteristic. If the lioness were given a mane, she would soon dispense with it. It makes no sense for her to bother with it, as it is a hindrance to her role. To say that a whimisical creator could have created them the same is to say that the creator creates things that won’t work.
    Why would the creator insert traits inharmonious with the system as it is set up?

  25. Dave T. wrote:
    “I know you are already answering a number of people on this thread, and I don’t want to pile on… Health is typically indicated by a normal range that includes both a maximum and minimum… our common experience [is] that health resides in a mean, and that both the excessive and defective conditions are unhealthy.”

    Hi Dave,
    I’m happy to respond. By the way, I’d like to continue our discussion of the significance of ‘form’ on the Origins of Mind thread once things slow down here. For now, I see that you’ve given me another Aristotelian concept (the mean) to address.

    It is true that most nominally positive traits can be carried to undesirable extremes. A football-field-sized peacock tail would be most impressive, but not very healthy. But this fact will not necessarily be reflected in the peahen’s preference. The peahen may continue to unconditionally prefer larger, more elaborate tails, despite the fact that they eventually become excessively burdensome to their owners and their owners’ offspring. Allow me to explain.

    Let’s go back to our original, drab population. Within this population, plumage ranges from ratty and mangy, through mediocre, to brighter and sleeker (but still extremely drab relative to a modern peacock’s tail). The sleekest and brightest individuals may very well be the healthiest within the original drab population, even though they would eventually become unhealthy if their sleekness and brightness were increased without bound. Natural selection operates only on the existing range of phenotypes, and is “unaware” of the consequences of taking these characteristics to an extreme.

    Within the original population, the more strongly biased a female is toward brightness and sleekness, the better. Such a bias will cause her to consistently mate with the healthiest males, giving her genes the best chance of making it into future generations.

    There is empirical data for this kind of open-ended preference. Geese prefer sitting on a fake, soccer-ball-sized egg to a normal-sized one. Now, any genuine soccer-ball-sized goose egg has problems (not to mention the fact that it would have killed the goose to lay it), so the extreme is obviously unhealthy. But within the range of actual goose egg sizes, bigger eggs are generally more viable, so it benefits the geese to develop an open-ended preference for sitting on bigger eggs.

    Other studies show similar open-ended preferences for fake “mates” with exaggerated sexual characteristics. I vaguely remember a study where individuals (I think they were birds) courted fake, car-sized members of the opposite sex, as long as they had the right coloration patterns.

    Back to our drab birds. Once the plumage bias becomes established among females, an interesting thing happens. An unusually sleek and bright male will be reproductively more successful than his competitors, even if his sleekness and brightness are otherwise disadvantageous (in attracting predators, for example). While he my succeed in producing more offspring, the obvious question is, will the offspring themselves manage to survive and reproduce? If not, the male’s sleekness and brightness did not help his genes propagate themselves. If yes, then the male’s descendants will outnumber those of his competitors, and the genes for extra sleekness and brightness will eventually become fixed in the population.

    The key point: once the bias is established in the female population, the males have ‘incentive’ to evolve brighter and sleeker plumage, as long as the incremental improvement in mating success is not outweighed by the decrease in ecological success. Each additional step toward sleekness and brightness has a higher ecological cost. Sleekness and brightness increase until a point is reached where the reproductive benefit is counterbalanced by the ecological cost, and the selection pressure toward sleekness and brightness becomes zero. In economic terms, the peacocks keep “spending” on their plumage until the marginal cost of additional sleekness is equal to its marginal benefit.

    Note that the equilibrium point is *not* optimum for the species as a whole. Evolution does not work for the long-term benefit of the species, but rather for the short-term benefit of the genes themselves.

    Since your original question was phrased in terms of the mean, let’s translate back into Aristotelian language. The Aristotelian mean for brightness and sleekness occupies an intermediate position on the spectrum of possible values. The entire range of *actual* brightness and sleekness in the original drab population is less than the Aristotelian mean of *possible* brightness and sleekness. As a result, the population evolves toward the Aristotelian mean, becoming brighter and sleeker. Because of the open-ended preference of the females, evolution “overshoots” the Aristotelian mean and stabilizes at an equilibrium point where brightness and sleekness are greater than the Aristotelian mean (or to be more precise, greater than the Aristotelian mean defined relative to ecological success alone).

    Regards,
    Valerie

  26. Hello again, PaV.

    You wrote:
    “Seems to me that cats mate at night. Can you make out that difference at night?”

    If there’s a full moon, yes. But the question is not whether *I* can make out the difference, it’s whether *they* can. Their eyes are a lot more sensitive than mine.

    “More seriously, has any experiment been done to prove that this kind of selection actually takes place?”

    Sure. I found a nice description of three such experiments in “The Red Queen”, by Matt Ridley:
    “It took a series of ingenious Scandinavians to establish that female birds really do pay attention to male plumes when choosing a mate. Anders Moller, a Danish scientist whose experiments are famously clever and thorough, found that male swallows with artificially lengthened tails acquired mates more quickly, reared more young, and had more adulterous affairs than males of normal length. Jakob Hoglund proved that male great snipe, which display by flashing their white tail feathers at passing females, could be made to lure more females by the simple expedient of having white typing-correction fluid painted onto their tails. The best experiment of all was by Malte Andersson, who studied the widow bird of Africa. Widow birds have thick black tails many times the lengths of their bodies, which they flaunt while flying above the grass. Andersson caught thirty-six of these males, cut their tails, and either spliced on a longer set of tail feathers or left them shortened. Those with elongated tails won more mates than those with shortened tails or tails of unchanged length. Tail-lengthening experiments in other species that have unusually long tails have similarly boosted male success.”

    You wrote:
    “And in the case of the finches, the beak sizes arose quickly and then went back to their original size when the weather changed back. This is no more than adaptation.”

    Yes, and adaptation is exactly what we’re talking about, and what natural selection produces. Even most of your fellow ID supporters (including Jonathan Wells) acknowledge that natural selection can drive microevolution, such as variations of beak size in finches or of pesticide resistance in insects (Wells’ only beef with the finch studies is that he believes they don’t support *macro* evolution).

    “You can’t account for this [finch beak variation] using the mathematics of the Modern Synthesis.”

    Could you refer me to a source which explains why?

    “You’re simply presuming that the females that “happen to be attracted to healthy males…tend to get more descendants”. Has that ever been tested and proven?”

    PaV, think about it. If you believe that health is heritable at all (and there’s overwhelming evidence that it is — look at the heritable susceptibility to diabetes, heart disease, and certain types of cancer in humans), then females who choose unhealthy mates will have offspring who, on average, are less healthy than those of females who choose healthy mates. Unhealthy individuals tend to die sooner and reproduce less successfully than healthy individuals. Over time, this means that unhealthy traits will tend to get weeded out of the population. If they didn’t, we’d have a population full of people with severe genetic diseases. If the unhealthy traits get weeded out of the population, then the individuals choosing mates with those traits will also get weeded out, since their genes become associated with the genes of their mates.

    “And why go by tail-feathers? Why not make sticking out your tongue part of the mating ritual? Wouldn’t that make more sense?”

    If tongue displays were a better indicator of health in the original population than tail-feathers, then sure. There are many mating displays in nature that are equally or more bizarre to human eyes than tongue displays.

    “You make it sound like a “Far Side” cartoon. The peacocks are huddled around the local tavern’s bar. One peacock says to the other, “Yeah, Sarah’s really been eyeing my feathers. You know, I think that one’s going to bring me a lot of great-great grandchildren.” Peacocks can’t think like we do. They simply live and die. They don’t worry about ‘posterity’; only humans do that.”

    When I said “It pays them in the sense that they get their genes into future generations”, I didn’t mean that they’re conscious of the payoff. When Dawkins wrote of “selfish” genes, do you think he meant that genes are literally, consciously selfish?

    The peacocks with elaborate tails are sought after by peahens. Less-endowed peacocks are not. Is it any surprise, then, that the genes for elaborate tails become fixed in the population? The peacocks don’t have to “decide” to have long tails. It just happens, over time.

    “You’ve been arguing that NS is bring about all these changes because of variable rates of generation due to the “healthy” (colored tails) males. And you say that even the tiniest of advantages will spread. And here you’re admitting that some birds don’t even breed when food is scarce, or that they might reduce their brood size. This sounds like a much more important determinant of “great-great-grandchildren” than colored tail-feathers.”

    It’s not either-or. Both traits improve the likelihood of descendants. A bird that refrains from breeding in conditions of scarcity actually increases the number of its descendants. If you produce a full-sized brood when food is scarce, the chicks may all die due to lack of food. You may die also, because (if you’re female) you’ve wasted a huge amount of energy producing eggs, and whether male or female, you have wasted a large amount of energy feeding the young, and less on feeding yourself. Refraining from breeding thus increases the likelihood that you’ll live to breed again when food is abundant.

    “You have to admit that this sure sounds like you’re saying: “Natural selection directs things along in an undirected way.” And that sort of statement, as they say, doesn’t add up, I’m afraid.”

    When IDers and Darwinians argue over whether evolution is “directed”, they’re arguing over whether it is directed by an intelligence. Darwinians certainly don’t believe that evolution is undirected in the sense of being completely random, Variation may be more-or-less random, but selection itself certainly is not.

    “So females have an instinct to propagate her genes. Do birds know what genes are? I know that sounds facetious, silly; but, the reality is that birds have an instinct to breed—no one would deny that; yet, to say that she wants to ‘ensure that her offspring will be able to attract mates…’, well, that sounds way too anthropomorphic to pass as science for me.”

    Again, this is like thinking that “selfish” in “a selfish gene” means *consciously* selfish. The peahens simply find themselves attracted to males with elaborate tails. There is no conscious deliberation. It is visceral, like the attraction men seem to feel for Angelina Jolie.

    But that attraction to showy males means that the female’s male offspring are more likely to have showy tails, which means they are more likely to attract females and produce offspring. If most of the females prefer showy males, then a female who prefers plainer males is less likely to produce successful male offspring, because her sons will have plainer tails which are less attractive to the female population at large.

    “I sort of had my tongue in my cheek when I was talking about the “feedback loop.””

    Oh. Sometimes I can’t tell when you’re kidding vs. honestly mistaken.

    “I see no doubt,as you present the argument, that this is circular reasoning. Circular reasoning involves assuming as a premise part, or all, of what you propose to demonstrate…
    The argument goes something like this:
    A.) Some peacocks developed colored tail-feathers.
    B.) Peahens preferred the colored tail-feathers.
    C.) As a result, all peacocks have colored tail-feathers.”

    Please see my reply (above) to Dave T. (taciturnus), where I explain how the preference arises in the first place. It’s not a circular argument.

    “If animals produce sexually, and one sex is ’showy’, the other sex is, of course, going to be the ‘choosy’ one. What other options are there? Is the one sex going to mate with itself? So in what way is this a ‘prediction’? It’s a tautology again.”

    If evolution is true, you’re right: the ‘showy’ sex will be the opposite of the ‘choosy’ sex. That’s my point.

    But a creator/designer could have arranged for the females to be brightly colored, with drably colored males competing for their attention. Or he could have made the females court the males, despite the fact that females invest more in the offspring. The fact that we do not see this in nature suggests that evolution is the better explanation for why things are the way they are.

    Hope this helps,
    Valerie

  27. Valerie,

    The key step seems to be the association of “health” and “brighter than normal plumage.” Once this association is made, it is a straightforward matter of logic to explain how bright plumage comes to predominate in peacocks.

    You explain the association of “health” and “brighter than normal plumage” with the statement that, in an original drab population, the sleekest and brightest individuals might very well have been the healthiest. And maybe they were. But doesn’t the assumption that they were simply assume the question at issue, which is how the bias towards bright and shiny plumage was originally introduced in the peacock population? That seems to be the essence of the “just-so” story. Why do peacocks have bright and sleek feathers? Because, at some time in the past, a peacock was born with feathers brighter and sleeker than all the others who was also healthier than all the others.

    Cheers,
    Dave T.

  28. Valerie,

    “But a creator/designer could have arranged for the females to be brightly colored, with drably colored males competing for their attention. Or he could have made the females court the males, despite the fact that females invest more in the offspring. The fact that we do not see this in nature suggests that evolution is the better explanation for why things are the way they are.”

    As I already exlained in post 24, this is just plain goofy. You have decided that a designer “could have” done anything, including created things that have no logical way to work. It’s no fair making up a thoroughly magical storybook designer, then comparing that to the real world, and saying see, science predicted it.

  29. “The key step seems to be the association of “health” and “brighter than normal plumage.” Once this association is made, it is a straightforward matter of logic to explain how bright plumage comes to predominate in peacocks.”

    Hi Dave,
    The cool thing about sexual selection is that it explains not just why bright plumage comes to predominate, but why the brightness gets pushed to the baroque extreme exhibited by peacocks.

    “Why do peacocks have bright and sleek feathers? Because, at some time in the past, a peacock was born with feathers brighter and sleeker than all the others who was also healthier than all the others.”

    Keep in mind that the original population was probably not peacocks, but rather some ordinary-looking predecessor species. And for the preference to become established, it was certainly not just one bird that happened to be born who was bright and sleek as well as healthy. The correlation between sleekness and health had to have been widespread in the population; otherwise a female who preferred sleekness would have been “wrong” most of the time, and the preference would not have persisted.

    Since you and PaV seem to be skeptical about the existence of correlations between health and appearance which can lead to the sexual selection of certain traits, consider:
    1. Skin blemishes are often an indication of disease in humans.
    2. So is skin color, with sallowness or excessive paleness being tip-offs.
    3. Poultry farmers know that the color of a rooster’s comb and wattles is indicative of his health.
    4. Many diseases cause birds to lose feathers.
    5. From my own experience, sick birds and cats will often stop grooming themselves, with highly visible results.
    6. The roach (a fish species) grows fewer tubercules on its skin when infested by parasites. Females prefer males with more tubercules.
    7. In many animals, the condition of the eyes is a strong indicator of health or sickness.

    Remember that the indicator does not have to be blatant. A subtle indicator can get the process of sexual selection started, as long as it is reliable. Fisher’s mechanism then takes care of amplifying the indicator to the extremes we see in species like peacocks.

  30. Hi avocationist,

    Sorry — I didn’t mean to ignore your previous comment.

    You wrote:
    “this is just plain goofy. You have decided that a designer “could have” done anything, including created things that have no logical way to work. It’s no fair making up a thoroughly magical storybook designer, then comparing that to the real world, and saying see, science predicted it.”

    Phillip Johnson proposed the “magical storybook designer”, not me. Look again at the Johnson quote from earlier in the thread:

    “…what I find intriguing is that Darwinists are not troubled by the unfitness of the peahen’s sexual taste. Why would natural selection, which supposedly formed all birds from lowly predecessors, produce a species whose females lust for males with life-threatening decorations? The peahen ought to have developed a preference for males with sharp talons or mighty wings. I don’t know what creation-scientists might suppose, but it seems to me that the peacock and peahen are just the kind of creatures a whimsical Creator might favor, but that an ‘uncaring mechanical process’ like natural selection would never permit to develop.”

    He is saying that peacock tails are “life-threatening decorations” that natural selection never would have produced, but just the kind of goofy thing that a whimsical creator might produce. The point of my comments in this thread was to show that his sexual selection *can* account for the peacock’s tail.

    You wrote:
    “I think it is a stretch for SS theory to take credit for “predicting” something which is really inevitable, i.e., that the non-choosy sex will be showier. It’s like saying competitors compete.”

    From your other comment:
    “Even if the whimsical creator had made them the same, they would not have stayed that way. The peahens would have dropped the characteristic. If the lioness were given a mane, she would soon dispense with it. It makes no sense for her to bother with it, as it is a hindrance to her role. To say that a whimisical creator could have created them the same is to say that the creator creates things that won’t work.
    Why would the creator insert traits inharmonious with the system as it is set up?”

    I agree that it is inevitable that the non-choosy sex will become showier over time, *if evolution is operating*. When you say that peahens would have shed their elaborate tails and that lionesses would have dropped their manes, you seem to be saying that evolution would have caused them to drop these features. I agree wholeheartedly. The sexual selection argument applies whether the population was put there originally by evolution or by creation/design.

    As for asking why the creator would “insert traits inharmonious with the system as it is set up”, be careful. ID proponents, including our weblog host, are constantly warning that we should not impose our standards of optimality on the work of the designer — see Dembski’s essay “Intelligent Design is not Optimal Design”:

    http://www.designinference.com.....sponse.htm

    You risk arousing their ire by suggesting that the designer “wouldn’t have done it that way”.

  31. Valerie,

    I don’t doubt at all the correlation between health and appearance. What I doubt is that the correlation between health and appearance in current populations is an explanation for how the correlation between health and that particular appearance came about in the first place. For instance, you wrote that pale skin is an indicator of ill health in human beings. That is true, as I used the same example in an earlier post, but it is also true that excessively bright skin is also a sign of ill health. That’s why human skin maintains a stable color over generations. Describing the current relationship of human skin color to health does nothing to explain the origin of that relationship.

    Your original hypothesis started with the following two points:

    “1. You have a population of birds with quite ordinary plumage.

    2. The healthiest birds, as a byproduct of their health, produce more or brighter feathers.”

    How does #2 follow from #1? Why don’t the healthiest birds in this population have quite ordinary plumage, since the defining characteristic of this population is its ordinary plumage? The healthiest of my son’s 16 gerbils have ordinary, dull fur, fur that is neither excessively shiny nor excessively dull. The only way #2 follows from #1 is if we assume in the ancient population the same relationship between health and plumage in the current population, which means we haven’t really explained the relationship but merely assumed it in our hypothesis.

    If the argument is that bright feathers have always been an indicator of health in peacocks (or their ancestors), even when the population norm for peacocks was dull feathers, then the argument is logically solid but trivially true.

    It seems like anything at all could be explained by this method. Why do my son’s gerbils have a dull brown coat? Well, the population of gerbils used to all have shiny fur, but then gerbils were born with the true, healthy, dull fur, the females selected for it, and the rest is history.

    Cheers,
    Dave T.

  32. Hello Valerie:
    I wrote: “More seriously, has any experiment been done to prove that this kind of selection actually takes place?”
    You wrote:
    “Sure. I found a nice description of three such experiments in “The Red Queen”, by Matt Ridley:
    ’It took a series of ingenious Scandinavians to establish that female birds really do pay attention to male plumes when choosing a mate. Anders Moller, a Danish scientist whose experiments are famously clever and thorough, found that male swallows with artificially lengthened tails acquired mates more quickly, reared more young, and had more adulterous affairs than males of normal length. Jakob Hoglund proved that male great snipe, which display by flashing their white tail feathers at passing females, could be made to lure more females by the simple expedient of having white typing-correction fluid painted onto their tails. The best experiment of all was by Malte Andersson, who studied the widow bird of Africa. Widow birds have thick black tails many times the lengths of their bodies, which they flaunt while flying above the grass. Andersson caught thirty-six of these males, cut their tails, and either spliced on a longer set of tail feathers or left them shortened. Those with elongated tails won more mates than those with shortened tails or tails of unchanged length. Tail-lengthening experiments in other species that have unusually long tails have similarly boosted male success.’
    This proves that plumage is involved in mating. It doesn’t, however, prove that bright/longer plumage is an indicator of health in these birds.
    I wrote:
    “And in the case of the finches, the beak sizes arose quickly and then went back to their original size when the weather changed back. This is no more than adaptation.”
    You wrote: “Yes, and adaptation is exactly what we’re talking about, and what natural selection produces. Even most of your fellow ID supporters (including Jonathan Wells) acknowledge that natural selection can drive microevolution, such as variations of beak size in finches or of pesticide resistance in insects (Wells’ only beef with the finch studies is that he believes they don’t support *macro* evolution).”
    Then why do you call it ‘evolution’ and not ‘adaptation’, which it rightly is. I concede that NS does play some role in nature; but I become more suspect of it the more experiments I read about. I think its value is highly overrated even in adaptational events.
    I wrote: “You can’t account for this [finch beak variation] using the mathematics of the Modern Synthesis.”
    You wrote: “Could you refer me to a source which explains why?”
    Just get a formula for genetic load, come up with a population number and selection value that are appropriate for Galapagos and beak size, respectively. You’re generally dealing with huge numbers for fixation to take place. That’s not an insurmountable problem given enough ‘time.’ But that’s the problem here; it’s happening on too short a time period to believe that the mechanisms proposed by the Modern Synthesis are at work in bringing this about.
    I wrote: “You’re simply presuming that the females that “happen to be attracted to healthy males…tend to get more descendants”. Has that ever been tested and proven?”
    “PaV, think about it. If you believe that health is heritable at all (and there’s overwhelming evidence that it is — look at the heritable susceptibility to diabetes, heart disease, and certain types of cancer in humans), then females who choose unhealthy mates will have offspring who, on average, are less healthy than those of females who choose healthy mates. Unhealthy individuals tend to die sooner and reproduce less successfully than healthy individuals. Over time, this means that unhealthy traits will tend to get weeded out of the population. If they didn’t, we’d have a population full of people with severe genetic diseases. If the unhealthy traits get weeded out of the population, then the individuals choosing mates with those traits will also get weeded out, since their genes become associated with the genes of their mates.”
    Valerie, think about it. Do women in their twenties, marrying men in their twenties, think about ‘heritable susceptibility to diabetes, heart disease, and certain types of cancer’? Do they ask these questions on the first date, or the second? And I’m afraid that peahens don’t know what cancer and diabetes are.
    The problem here is that though it’s a reasonable assumption that ‘health’ matters, that doesn’t mean that this is what drives NS. Like I said, if health was such a determiner for breeding success, then birds ought to be sticking their tongues out at each other.
    You wrote in response to this same kind of comment:
    “If tongue displays were a better indicator of health in the original population than tail-feathers, then sure. There are many mating displays in nature that are equally or more bizarre to human eyes than tongue displays.”
    Then, tell me, Valerie, are there birds with elongated and colored tongues? I’m being more than just facetious here. And, if health is the critical parameter to reproductive success, then why don’t all bird species stick their tongues out?
    I wrote: “You make it sound like a “Far Side” cartoon. …..
    “When I said “It pays them in the sense that they get their genes into future generations”, I didn’t mean that they’re conscious of the payoff. When Dawkins wrote of “selfish” genes, do you think he meant that genes are literally, consciously selfish?”
    Then why use the anthropomorphic language? It isn’t accurate. In fact, it’s misleading. And it’s this that’s precisely the problem with Dawkins: his is a science of metaphor. If I want metaphor, I’ll read poetry, thank you.
    I wrote: “You’ve been arguing that NS is bring about all these changes because of variable rates of generation due to the “healthy” (colored tails) males. And you say that even the tiniest of advantages will spread. And here you’re admitting that some birds don’t even breed when food is scarce, or that they might reduce their brood size. This sounds like a much more important determinant of “great-great-grandchildren” than colored tail-feathers.”
    “It’s not either-or. Both traits improve the likelihood of descendants. A bird that refrains from breeding in conditions of scarcity actually increases the number of its descendants. If you produce a full-sized brood when food is scarce, the chicks may all die due to lack of food. You may die also, because (if you’re female) you’ve wasted a huge amount of energy producing eggs, and whether male or female, you have wasted a large amount of energy feeding the young, and less on feeding yourself. Refraining from breeding thus increases the likelihood that you’ll live to breed again when food is abundant.”
    Frankly, Valerie, this just sounds like the kind of ad hoc argument that spelled the downfall of Ptolomeic theory: statements that are untested, perhaps even unknowable, are just simply introduced to make an otherwise valid refutation of a theory go away. I don’t consider that science.
    I wrote: “So females have an instinct to propagate her genes. Do birds know what genes are? I know that sounds facetious, silly; but, the reality is that birds have an instinct to breed—no one would deny that; yet, to say that she wants to ‘ensure that her offspring will be able to attract mates…’, well, that sounds way too anthropomorphic to pass as science for me.”
    Again, this is like thinking that “selfish” in “a selfish gene” means *consciously* selfish. The peahens simply find themselves attracted to males with elaborate tails. There is no conscious deliberation. It is visceral, like the attraction men seem to feel for Angelina Jolie.
    And, again, why use language in such a loose way? Why not stick to what you know, what you assume, and what can be demonstrated? You can’t demonstrate that females have an instinct to propagate her genes. Why not simply admit that you’re ‘assuming’ it.
    “But that attraction to showy males means that the female’s male offspring are more likely to have showy tails, which means they are more likely to attract females and produce offspring. If most of the females prefer showy males, then a female who prefers plainer males is less likely to produce successful male offspring, because her sons will have plainer tails which are less attractive to the female population at large.”
    But, of course, doesn’t this logic say that if the peahens now to start to be attracted to large wing feathers, the tail feathers will then shrink and the wing feathers will elongate, and the peacock will become a better flyer, and hence, less vulnerable to predators? Yes, or no? If you say ‘no’, then this undercuts your theory; if you say ‘yes’, then you’re admitting that selection has brought about something that makes the peacock less ‘fit.’ How do you answer?
    I wrote: “I see no doubt, as you present the argument, that this is circular reasoning. Circular reasoning involves assuming as a premise part, or all, of what you propose to demonstrate…
    The argument goes something like this:
    A.) Some peacocks developed colored tail-feathers.
    B.) Peahens preferred the colored tail-feathers.
    C.) As a result, all peacocks have colored tail-feathers.”

    Please see my reply (above) to Dave T. (taciturnus), where I explain how the preference arises in the first place. It’s not a circular argument.
    I did look. Here’s a quote: “Within the original population, the more strongly biased a female is toward brightness and sleekness, the better. Such a bias will cause her to consistently mate with the healthiest males, giving her genes the best chance of making it into future generations.” Your ‘escape’ from circularity depends on averring that the female bias develops separately from the male sexual secondary characteristics. This averring is all hypothetical. We know ‘what’ biases birds have, but we don’t know ‘why’ they have them, or ‘how’ they came about. The circularity of the argument stems from the fact that for the theory to work you must have—simultaneously—the female preference for the male trait, AND, the male developing that very trait. Your explanations—in your mind—might seem clever, and, even correct; but, as has been stated, we really have no more than “just-so” stories.
    I wrote: “If animals produce sexually, and one sex is ’showy’, the other sex is, of course, going to be the ‘choosy’ one. What other options are there? Is the one sex going to mate with itself? So in what way is this a ‘prediction’? It’s a tautology again.”
    If evolution is true, you’re right: the ’showy’ sex will be the opposite of the ‘choosy’ sex. That’s my point.
    Thus, if evolution is false, then there won’t be any differences between a ‘showy’ sex and a ‘choosy’ sex. Can you tell the difference between turtledoves? Sparrows? Crows?
    But a creator/designer could have arranged for the females to be brightly colored, with drably colored males competing for their attention. Or he could have made the females court the males, despite the fact that females invest more in the offspring. The fact that we do not see this in nature suggests that evolution is the better explanation for why things are the way they are.
    Unfortunately, evolution—really neo-Darwinism/Modern Synthesis—can explain anything and everything; but, that’s not necessarily good. It makes it unfalsifiable. All you need for an ‘evolutionary’ explanation is to notice what is ‘good’ about a situation/a species/a part of anatomy/etc, etc, and then invent a scenario that might have brought about this ‘good.’ This calls for a great imagination. But it doesn’t call for much critical analysis. Whether you believe your story about peacock plumage, or not, to me it sounds like nothing more than that: a story. “Once upon a time there was a peahen who love plumage…..” I’m really quite surprised it doesn’t sound like that to you.

  33. Dave,

    Your objection is that we can’t prove that brighter feathers were correlated with health in the ancestral population. That strikes me as analogous to coming upon the aftermath of an evident explosion (radial debris pattern, worst damage closest to the center, evidence of high temperature, explosive residue) but arguing that we don’t really know that the explosion happened, because we don’t know for sure that there was something there capable of igniting the blast. A reasonable inference is that something did indeed ignite it.

    And even if you don’t accept the initial correlation between health and feather brightness, it remains true that the Fisherian mechanism can explain the aftermath, provided that an initial preference for brightness arises by any mechanism at all. An initial push is needed (from any source), and then the process becomes self-sustaining.

    “If the argument is that bright feathers have always been an indicator of health in peacocks (or their ancestors), even when the population norm for peacocks was dull feathers, then the argument is logically solid but trivially true.”

    No, the argument is that feathers from the bright end of the normal range were indicative of health. The Fisherian mechanism takes care of turning “slightly brighter than normal” into the “off-the-charts showy” that we see in modern peacocks.

    “It seems like anything at all could be explained by this method.”

    In other words, you’re claiming that sexual selection theory is not falsifiable. But this is simply not true.

    Here are a couple of scenarios that would falsify SS theory:

    1. As I mentioned in an earlier comment, if you looked across many species and found that the ‘choosy’ sex was the brightly colored and ornamented one while the ‘showy’ sex was relatively drab, then sexual selection theory would be falsified.

    2. A bird species with extremely long tail streamers was studied. The researchers found, by systematically shortening some tail streamers and lengthening others, that the birds with the longer streamers paid a price: they were less successful in catching insects than the birds with the shorter streamers. If it had then turned out that females were indifferent to tail streamers, sexual selection theory would have been falsified. (As it happens, the females prefer males with longer tails, as predicted by SS theory. The males have made the Fisherian bargain of trading feeding efficiency for sexual attractiveness.)

    I’ve been fielding questions for a while. Now, if you don’t mind, it’s my turn to put you on the spot: Do you have an alternative theory to explain the regularities that SS theory makes sense of, including the gaudy extreme to which peacock’s tails have been pushed?

  34. I just finished reading the very interesting series of posts between Valerie (whom I would like to personally thank for her serious and in-depth answers)and others, and I find myself a little bit surprised by the ongoing argument about sexual selection modifying the species over time. Why is this controversial from the perspective of design? It makes complete sense to me that over time, certain traits would spread across a population as a result of such pressures, and this doesn’t seem to say anything about the issue of design; in other words, it doesn’t explain how the complex information necessary to bring about the existence of the trait in the first place came to be a part of the genome of the species. I think Phillip Johnson’s attitude toward the creator as some kind of a whimsical artist is a silly and undignified mess philosophically. This is where proponents of design, which is so self-evident in nature, get themselves into trouble. Realizing that the IMPLICATIONS of design are more intrinsically interesting than the bare FACT of design, they don’t seem willing to develop these implications further, possibly because they sense the quagmire of total disagreement which lies around that bend. Interestingly, I think that the implications of design can be quite practical and scientific as well. If certain systems in a developed being are seen as being the result of an designing intelligence, those systems are more likely to be understood as worthwhile intrinsically and respected. For example, medicine has long looked at women as men with different organs:) Recently, however, this view is changing radically. In fact, the deeper science looks at the male and female bodies, the more drastic the differences are becoming. This has tremendous implications for the treatment of disease, as well as for the culture which we create based upon our understandings. When a woman experiences significant intuitive and emotional changes during a certain part of her cycle, and this is a feature of a intentional design rather than a nasty by-product of brute forces, those changes might be seen as good and a potential source of significant psychic information. Rather than medicating such a woman, a design-inclined culture might encourage her to enter into her mood state as deeply as possible so as to extract from it the insights which are made available with such intensity during this time. Forgive the length of the digression, but the example sprung to my head! Anyway, to conclude it has always been my understanding, someone correct me if I am wrong, that selection pressures, environmental and otherwise, are perfectly acceptable aspects of an ID position.

  35. Valerie,

    “I agree that it is inevitable that the non-choosy sex will become showier over time, *if evolution is operating*. When you say that peahens would have shed their elaborate tails and that lionesses would have dropped their manes, you seem to be saying that evolution would have caused them to drop these features. I agree wholeheartedly. The sexual selection argument applies whether the population was put there originally by evolution or by creation/design.”

    I agree exactly with your last sentence. Perhaps a misunderstanding arises because you call it evolution, and I really don’t. Just as domestic breeding has the power to call forth great variety, so does sexual selection have at least some power to do that. There is no question that genetic variations can occur, be it called forth by natural selection, domestic intentional breeding, or sexual selection. So you take it as one more evidence for evolution, but I simply take it as the way things work at the species level. In the case of the lioness dropping a useless and cumbersome mane, that would be natural selection.

    “As for asking why the creator would “insert traits inharmonious with the system as it is set up”, be careful. ID proponents, including our weblog host, are constantly warning that we should not impose our standards of optimality on the work of the designer — see Dembski’s essay “Intelligent Design is not Optimal Design”:”

    Really that is not what I have done. I am not imposing standards on the designer. I am rather saying that the whole line of argument that the creator could do as he pleases when it goes against the way things must work should stop. You have asked why didn’t the designer simply force upon peahens the elaborate feathers even though they are the choosy sex. But we could make up all sorts of such possibilities and ask why he didn’t do it. Yet it appears that our world is a coherent place. Why didn’t the designer insert incoherent things as he pleased? Well, because they would have righted themselves, that’s why. You seem to assume that if there was a designer, that it means life is static. But as you see from the case of domestic breeds, there is tremendous room for adjustment.

  36. Hi, PaV.

    I’m enjoying our back-and-forth.

    You wrote:
    “This proves that plumage is involved in mating. It doesn’t, however, prove that bright/longer plumage is an indicator of health in these birds.”

    First, plumage *is* an indicator of health. See the quote from peafowl.org in my earlier comment. Second, beyond a certain point, it doesn’t matter whether increases in brightness or fullness of plumage correlate with increased health. Once the Fisherian feedback loop is activated, it will ‘push’ the plumage toward increased ‘showiness’, *even* at a cost to the owners. Once the feedback loop is well underway, the females will continue to prefer elaborate plumage simply because the other females do. A female variant who prefers drab males will produce drab male offspring who are unattractive to other females, and thus less likely to leave offspring of their own. Thus a mutant preference for drabness will die out in a population where most of the females prefer elaborate plumage.

    “Then why do you call it ‘evolution’ and not ‘adaptation’, which it rightly is.”

    Because adaptation *is* a form of evolution. That’s why ID supporters are willing to concede that microevolution (which is adaptation writ small) happens. Adaptation is central to evolution. Where did you get the idea that it was excluded?

    “Just get a formula for genetic load, come up with a population number and selection value that are appropriate…it’s happening on too short a time period to believe that the mechanisms proposed by the Modern Synthesis are at work in bringing this about.”

    Can you give me what you consider to be reasonable numbers for all of the parameters, so I can assess their reasonableness and do the calculation myself?

    “Do women in their twenties, marrying men in their twenties, think about ‘heritable susceptibility to diabetes, heart disease, and certain types of cancer’? Do they ask these questions on the first date, or the second? And I’m afraid that peahens don’t know what cancer and diabetes are.”

    Again, you’re assuming that these preferences involve a conscious deliberation regarding health and eventual reproductive success. They don’t. Example: Men are most attracted to women with a waist-to-hip ratio that correlates with maximum fertility. If a man tries to start an affair with a woman at the office who has that ratio, do you think he’s doing it because he has consciously decided that she will be able to provide him with healthy offspring? Hardly. A child is the last thing he wants. He’s doing it because evolution has shaped his instinctual standards of beauty to correspond to health and fertility. He simply feels attracted to her, and he acts on the attraction.

    From the abstract of an article by Devendra Singh:
    “One of the bodily features, waist-to-hip ratio (WHR), is a reliable indicator of a female’s reproductive age, sex hormone profile, parity and risk for various diseases. Systematic variation in the size of WHR also systematically affects the judgment of female attractiveness, healthiness, and youthfulness. This article summarizes recent findings about the relationship between female’s WHR and various factors affecting reproductive capability and risk for diseases.”

    “Then, tell me, Valerie, are there birds with elongated and colored tongues? I’m being more than just facetious here. And, if health is the critical parameter to reproductive success, then why don’t all bird species stick their tongues out?”

    What would be the initial “push” that would start a Fisherian cycle of birds sticking their tongues out? Plumage is a better bet, being more obvious, visible all the time, and visible from greater distances.

    “…why use the anthropomorphic language? It isn’t accurate. In fact, it’s misleading. And it’s this that’s precisely the problem with Dawkins: his is a science of metaphor. If I want metaphor, I’ll read poetry, thank you.”

    We use anthropomorphic language because using non-anthropomorphic language deadens the prose and makes it harder to understand. Try expressing the idea of the selfish gene using non-anthropomorphic language and you’ll see what I mean. Moreover, Dawkins is careful to stress that it *is* a metaphor, lest anyone miss the obvious point.

    If you dislike metaphors, you may want to stop reading science. Scientists use metaphors constantly. Random examples:

    1. Nuclear winter. A pedant could say, “If the bombs explode in the summer, it’s not a nuclear winter.” The rest of us have no trouble with the metaphor.

    2. Launch window. Only a pedant goes looking for the glass.

    3. Broadcast. Originally a way of sowing seeds. We don’t flinch when hearing it applied to radio, television, or the Internet.

    4. Proton donors. When chemists speak of acids as proton donors, only a pedant thinks of it as a conscious “gift”.

    “…statements that are untested, perhaps even unknowable, are just simply introduced to make an otherwise valid refutation of a theory go away. I don’t consider that science.”

    Please explain how evolution is incompatible with the fact that some species refrain from breeding in times of scarcity. Your objection seems to be based on the common misunderstanding that evolution’s “goal” (metaphor alert) is to maximize the number of offspring. This is false. Having a zillion offspring is no “good” if they all die before reproducing. It’s even “worse” if the parents die because they “insisted” on breeding. To refrain from breeding during tough times is a “smart” solution to the problem of scarcity that evolution should “favor”. It is hardly a refutation of evolution.

    “You can’t demonstrate that females have an instinct to propagate her genes. Why not simply admit that you’re ‘assuming’ it.”

    Because I’m not assuming it. When given a choice, a female will pick healthy males over unhealthy ones. Healthy mates tend to produce healthy offspring, so her genes are propagated more successfully.

    “But, of course, doesn’t this logic say that if the peahens now to start to be attracted to large wing feathers, the tail feathers will then shrink and the wing feathers will elongate, and the peacock will become a better flyer, and hence, less vulnerable to predators? Yes, or no? If you say ‘no’, then this undercuts your theory; if you say ‘yes’, then you’re admitting that selection has brought about something that makes the peacock less ‘fit.’ How do you answer?”

    First, a preference for large wing feathers and reduced tail feathers will not spread in a population where the other females like big tails. See my argument above.

    Second, you seem to think that if large tail feathers make a peacock more vulnerable to predators, this is somehow a knock against sexual selection. Precisely the opposite: sexual selection *predicts* that peacocks will maintain the tails even if the tails make them more vulnerable to predators, as long as the increased vulnerability is offset by more success with the peahens. This is why SS theory is so important — it explains something that seems paradoxical if you think selection only operates on traits affecting survival.

    “The circularity of the argument stems from the fact that for the theory to work you must have—simultaneously—the female preference for the male trait, AND, the male developing that very trait.”

    Not true. If brighter feathers correlate to better health in the original population, then that’s all you need for the Fisherian cycle to start. The females can evolve the preference in response to the male trait. The preference is *not* a prerequisite.

    “Thus, if evolution is false, then there won’t be any differences between a ‘showy’ sex and a ‘choosy’ sex. Can you tell the difference between turtledoves? Sparrows? Crows?”

    That’s not what I said. I wrote “If evolution is true, you’re right: the ’showy’ sex will be the opposite of the ‘choosy’ sex.” In other words, if males are showy, females will be choosy, and vice-versa.

    “Unfortunately, evolution—really neo-Darwinism/Modern Synthesis—can explain anything and everything; but, that’s not necessarily good. It makes it unfalsifiable.”

    Sexual selection *is* falsifiable. See my comment to Dave for examples of how it could be falsified.

    “…it sounds like nothing more than that: a story. “Once upon a time there was a peahen who love plumage…..” I’m really quite surprised it doesn’t sound like that to you.”

    Labeling it a “story” doesn’t make it untrue. By the way, the correlation between health and plumage would come first, and the peahen preference would come second.

    The *only* starting condition required for a sexual selection “story” to unfold is a correlation between health and appearance. Far from being a “just-so story”, the rest of it unfolds strictly according to the Fisherian mechanism. To successfully refute it, you need to show either that 1) there can be no correlation between health and the maximization of some visible aspect of appearance, or 2) that there is a defect in Fisher’s logic. So far you have done neither.

    I’ll make the same request of you as of Dave. Can you provide an alternate theory that explains why:

    1. Males tend to be showy, and females choosy, except in species where males invest more in raising the young than the females do.

    2. The most elaborate “ornamentation” is found on the side that does the courting, not on the side that does the choosing.

    3. Extreme ornaments, such as peacock tails, are maintained despite the cost in survivability to their owners.

    4. In species where those extreme ornaments exist, the opposite sex prefers mates with the most elaborate ornaments.

    All of these are predicted by sexual selection; their opposites are not. Can you offer an alternative theory of equal or greater predictive power?

    Regards,
    Valerie

  37. Tina,

    Thanks for the kind words. It’s nice to know that someone out there appreciates the effort I’m putting into my comments.

    I too am mystified by the controversy over the idea of sexual selection. Perhaps it is because sexual selection suggests that the traits in question (like the peacock’s tail) are augmented gradually over time by selecive pressure, when design theorists would prefer to think that they emerged all at once. I don’t know.

    Regards,
    Valerie

  38. avocationist wrote:
    “Perhaps a misunderstanding arises because you call it evolution, and I really don’t.”

    Hi Avocationist,

    Could be. I ran into the same problem with PaV, who didn’t think I should be using the word ‘evolution’ to encompass ‘adaptation’.

    “Why didn’t the designer insert incoherent things as he pleased? Well, because they would have righted themselves, that’s why.”

    Perhaps the designer likes to see things righting themselves, like a kid who turns bugs upside down in order to see them struggle upright again. Who knows? You have to make assumptions about the designer’s motives to decide what he would have done.

    The real point of this thread is discussing the objections of ID supporters to the idea of sexual selection. Phillip Johnson, the father of the ID movement, thinks that evolution would never have exaggerated the peacock’s tail to its current extent, and that a whimsical Creator is required. If he is correct, then evolution would have been unable to “right things” had the Creator decided to give peahens the elaborate tails instead of peacocks.

    The fact that we do not see peahens with big tails, and that all across nature we see evidence that conforms to the predictions of sexual selection, suggests one of the following:

    1. Evolution and sexual selection are operating, at least to some extent.
    2. Evolution and sexual selection are not operating, but the whimsical Creator designed nature to give the appearance that they are.

    Both you and I would choose #1. The difference is that I would go further and suggest that there is no designer.

  39. Valerie,

    I will answer your questions, but first I want to say that I think you are missing the point of my objections. I’m not a biologist and I am no expert in what constitutes health in peacocks. Usually health resides in a mean, but if, as you say, the showiest peacocks are also the healthiest, and always have been, I’ll accept that.

    My point is that the critical step in the argument is correlating the healthiest peacocks with those with the brightest feathers. Once this is done, it follows directly that peacock feathers will get brighter with every generation, even without sexual selection. Healthy birds tend to survive better (isn’t that almost the definition of health?), the showiest birds are usually the healthiest, therefore the showiest birds will survive. Q.E.D.

    I don’t claim to have an explanation as to why peacocks have bright and gaudy feathers. Maybe sexual selection is the answer… I don’t know. I just don’t see how we need to even bring sexual selection into it if the peacocks with the brightest and gaudiest feathers have also always been the healthiest peacocks.

    “1. Males tend to be showy, and females choosy, except in species where males invest more in raising the young than the females do.”

    The only reason I can think of for this situation is that showy males are more healthy in every species but those where males invest more in raising the young. If the showy males in these latter species were also always the healthy ones, like in peacocks, then I would expect them to become more showy over time as well.

    “2. The most elaborate “ornamentation” is found on the side that does the courting, not on the side that does the choosing.”

    I admit this puzzles me. The original premise of the argument was that “The healthiest birds, as a byproduct of their health, produce more or brighter feathers.” I suppose this holds true for peahens as well as peacocks. If the peahens with the brightest feathers are always the healthy ones, then why doesn’t peahen feathering become brighter over time? I suppose it could be argued that such peahens are more susceptible to predators, which is fine. Then it should follow that peahen populations not subject to predation (in captivity, for example) should become more showy over time. Is this happening?

    “3. Extreme ornaments, such as peacock tails, are maintained despite the cost in survivability to their owners.”

    This is because the peaocks with the bright, showy tails are also the healthiest. Healthy birds survive better than unhealthy ones.

    “4. In species where those extreme ornaments exist, the opposite sex prefers mates with the most elaborate ornaments.”

    This is because the mates with the most elaborate ornaments are the healthiest. Again, it is common sense that females prefer to mate with healthy males, and if the healthy males are always (or usually) the ones with the brightest, showiest feathers, then they will get the girls. My point is not that this argument is mistaken, only that the key step is the equation of health with showiness, and once this equation is accepted, everything else follows directly. The interesting question for me is: Why have the healthiest peacocks always been the showiest ones, going all the way back to the original populations? I don’t have an answer to this, and it seems neither does sexual selection theory, since it assumes it as one of its premisses. Once that evolutionary check is written, I grant that it is a simple matter to cash it out.

    Cheers,
    Dave T.

  40. Valerie,

    I think I can state my point succinctly. Showy feathers seem to be a paradox because they seem to have no direct link to survivability. In fact, they may even be deleterious because they might attract predators (although I know of some animals that use bright coloring to scare off predators.) But it turns out that showy feathers are directly correlated with health, and have always been so correlated, saecula saeculorum. Since health is closely associated with survival, it follows that the showiest birds will usually survive to propagate themselves. No problem, and the logic is airtight. For me, it leaves the most interesting question unanswered, which is the link between showiness and health.

    Cheers,
    Dave T.

  41. Hi Dave,

    Thanks for the clarifications. I think I understand better now what’s bugging you about the sexual selection argument.

    “My point is that the critical step in the argument is correlating the healthiest peacocks with those with the brightest feathers. Once this is done, it follows directly that peacock feathers will get brighter with every generation, even without sexual selection. Healthy birds tend to survive better (isn’t that almost the definition of health?), the showiest birds are usually the healthiest, therefore the showiest birds will survive.”

    “I think I can state my point succinctly. Showy feathers seem to be a paradox because they seem to have no direct link to survivability. In fact, they may even be deleterious because they might attract predators (although I know of some animals that use bright coloring to scare off predators.)”

    Yes, like the Amazonian butterflies that use color to advertise their inedibility, or the ones with large eyespots on their wings to confuse predators.

    I *do* think showy feathers are deleterious. To a predator, they must look like a neon sign saying “Eat me!”, not to mention that they must slow the peacock down when he is trying to flee. It’s a paradox: why does he carry around that tail if it reduces his survivability? Shouldn’t natural selection force the tails to be smaller? After all, the long tails may be an indicator of health, but they are surely not a prerequisite of health. Why doesn’t NS shorten the tails while retaining health?

    The genius of sexual selection theory is that it resolves the paradox. Why does the peacock grow that burdensome tail? Because peacocks with showy tails get the babes, and therefore produce more offspring than the peacocks with shorter tails. Having additional sex appeal is worth it, despite the cost in survivability, if it results in getting more genes into future generations.

    Why do peahens prefer the showy tails? Because all of the other peahens do. A variant peahen who prefers shorter-tailed males will produce shorter-tailed male offspring, who will then have poor luck with the predominantly long-tail-loving females. Genes for short-tail preference will therefore die out, overpowered by the long-tail majority. A peahen needs to prefer long-tailed males if she “wants” to propagate her genes.

    It’s a classic positive feedback loop: the males retain showy tails because the females demand it; the females retain the preference for showy tails because they “want” their male offspring to be successful with the females, who demand showy tails.

    It’s a ridiculous and wasteful situation. From the outside, we can see that the optimum thing to do would be to get rid of the huge tails and “recalibrate” the female’s aesthetics to accept more modestly-adorned males. This would benefit the males, who would survive better, and the females, whose sons would survive better, carrying their mothers’ genes with them. But evolution is blind and does not see the way out of the quagmire. The only means of escape would require simultaneous mutations in males and females across the entire population. The odds are astronomical against this. And so peacocks retain their tails, to their detriment but to our (and presumably peahens’) aesthetic delight. See this great photo:

    http://staff.washington.edu/an.....peahen.jpg

    How did peafowl get into this ridiculous situation? By Fisher’s mechanism. An initial correlation between feather brightness/size and health in the original, modest-looking population ignited a Fisherian feedback loop that led to the current absurd situation.

    Hopefully I’ve made the argument clearer. If so, you might want to reread my earlier comments from the new perspective to see if they make more sense.

    “Once that evolutionary check is written, I grant that it is a simple matter to cash it out.”

    Good. Let’s cash it and go have a beer.

    Regards,
    Valerie

  42. Valerie:

    We just seem to talk around each other. Here’s an example:
    I wrote: “You can’t demonstrate that females have an instinct to propagate her genes. Why not simply admit that you’re ‘assuming’ it.”
    You wrote: Because I’m not assuming it. When given a choice, a female will pick healthy males over unhealthy ones. Healthy mates tend to produce healthy offspring, so her genes are propagated more successfully.
    You state that ‘females have an instinct to propagate her genes.’ That implies a purpose to the act of breeding other than a sexual urge. In effect, you choose to answer the unease I have with this kind of statement in a way that doesn’t address my ill ease at all. You’re telling me that the end result of the mating ritual is—in your opinion, not mine—a more numerous progeny over several generations, etc. That might be the end result; but, incontrovertibly, it’s not the peahen’s instinct. Her instinct is to mate, and to mate in a certain way. That’s it. Nothing more.

    For whatever reason, you can’t see the error in your thinking, and it appears I’m helpless in pointing it out. So, it’s best the conversation be dropped. I think we’re just talking past each other at this point.

    Look at what follows:
    “But, of course, doesn’t this logic say that if the peahens now to start to be attracted to large wing feathers, the tail feathers will then shrink and the wing feathers will elongate, and the peacock will become a better flyer, and hence, less vulnerable to predators? Yes, or no? If you say ‘no’, then this undercuts your theory; if you say ‘yes’, then you’re admitting that selection has brought about something that makes the peacock less ‘fit.’ How do you answer?”
    You answer:
    First, a preference for large wing feathers and reduced tail feathers will not spread in a population where the other females like big tails. See my argument above.
    So let’s look at your argument up above: Here’s what you said:

    1. You have a population of birds with quite ordinary plumage.
    2. The healthiest birds, as a byproduct of their health, produce more or brighter feathers.
    3. Females who happen to prefer males with more/brighter plumage are reproductively more successful, because their offspring benefit from the genes of their healthy fathers.
    4. The preference for more/brighter feathers becomes widespread among the females of the population.
    Now you have the conditions for a classic positive feedback loop:
    You’ll notice that when you were laying out this scenario that you didn’t have a problem at all with one preference pushing out the other. Why is it not now allowed? And, yes, I know that you’re now going to talk about ‘health’, etc, so all we have to say is that the ‘healthiest’ peacocks now have enlarged wing feathers, etc. I’m afraid your argument is like a dog chasing its tail: endless and pointless.

    You wrote:
    I’ll make the same request of you as of Dave. Can you provide an alternate theory that explains why:
    1. Males tend to be showy, and females choosy, except in species where males invest more in raising the young than the females do. ……..
    You only need to explain it if you believe in Darwinism and that all life forms are the result of some kind of ‘selection’. Other than that, it doesn’t need explanation, only elaboration; viz., what we see in nature are peacocks with very colorful tail-feathers and peahens who are very attracted to them.

    Good luck, Valerie.

  43. Valerie,

    I guess I am not all that clear on what other ID folk think of sexual selection. To me, sexual selection is rather obvious, but like natural selection, Darwinists may be attributing more to its powers than it warrants. Because most of the workings of sexual selction are obvious, I have objected to allowing NDE to get credit for ‘predicting’ them. But, thinking about it today, I thought to myself that peacocks have all the hallmarks that we normally see among domestic, but not wild animals, and I found this:

    Peacocks have been kept as tame birds in India for over 3000 years.

    I suspect that peacock features may have been accentuated by human preference.

  44. PaV,

    Don’t give up! I think we’re almost there.

    You wrote:
    “You state that ‘females have an instinct to propagate her genes.’ That implies a purpose to the act of breeding other than a sexual urge.”

    From the peahen’s conscious perspective, she is just following her instinctive sexual urge, nothing else. Her genes, on the other hand, are “using” her libido to get themselves reproduced. By creating a preference for long-tailed males, they improve their success. The peahen is unaware of what her genes are trying to do, of course, and simply feels more desire for a long-tailed male.

    (Returning to an earlier point, imagine how clunky that paragraph would have been if I hadn’t used anthropomorphic language to describe what the genes “want” or “do”.)

    Here’s what I wrote: “For the female to propagate her genes, she needs to ensure that her offspring will be able to attract mates.” Now, I don’t mean that she consciously frets over when her son will finally start dating peahens. Evolution simply ensures that she is sexually attracted to the mates who will help her produce attractive sons.

    The desires are instinctual, but they serve an evolutionary rationale, because, after all, they are shaped by evolution. Except in the case of humans, the bearer of these desires is not conscious of their underlying evolutionary purpose.

    And humans are especially interesting, because not only do we (at least we Darwinian humans) understand why we feel such a visceral attraction to certain potential partners, but we can also consciously deliberate about their suitability. Often a struggle ensues between “gut” and “head”. But it remains true that the visceral desire is shaped by evolution, in humans as in all other animals. That is why 20-year-old men are not (except in rare cases) sexually aroused by eighty-year-old women, no matter how wise, bubbly, compassionate, loving, or wealthy they are. A man’s innate preference is tuned by evolution to favor women who are likely to be fertile.

    I wrote:
    “First, a preference for large wing feathers and reduced tail feathers will not spread in a population where the other females like big tails. See my argument above.”

    …but you referred to the wrong argument. Here’s the one I meant:
    “Once the feedback loop is well underway, the females will continue to prefer elaborate plumage simply because the other females do. A female variant who prefers drab males will produce drab male offspring who are unattractive to other females, and thus less likely to leave offspring of their own. Thus a mutant preference for drabness will die out in a population where most of the females prefer elaborate plumage.”

    Or as I put it to Dave:
    “Why do peahens prefer the showy tails? Because all of the other peahens do. A variant peahen who prefers shorter-tailed males will produce shorter-tailed male offspring, who will then have poor luck with the predominantly long-tail-loving females. Genes for short-tail preference will therefore die out, overpowered by the long-tail majority. A peahen needs to prefer long-tailed males if she “wants” to propagate her genes.”

    Finally, you wrote:
    “You only need to explain it if you believe in Darwinism and that all life forms are the result of some kind of ‘selection’. Other than that, it doesn’t need explanation, only elaboration; viz., what we see in nature are peacocks with very colorful tail-feathers and peahens who are very attracted to them.”

    But don’t you see the appeal of a theory which successfully explains *why* things are that way, rather than simply noting the facts and shrugging?

    And given that you are an ID supporter who doubts selection, would you then say that peafowl are the way they are because the designer made them that way? If so, it raises the question, why would he have done so in precisely the way that mimics the predictions of sexual selection theory? Isn’t it a “just-so story” to say that peafowl (and a huge number of other species) were designed in a way that just happens to correspond to the predictions of sexual selection theory?

    Regards,
    Valerie

  45. avocationist wrote:
    “Peacocks have been kept as tame birds in India for over 3000 years. I suspect that peacock features may have been accentuated by human preference.”

    You might be right.

    In any case, there are lots of elaborately ornamented species that have never been domesticated. Here are some examples of birds of paradise:

    http://www.accessexcellence.or.....eWin9.html
    http://www.accessexcellence.or.....Win10.html

    By the way, check out this amazing white peacock:

    http://en.wikipedia.org/wiki/I.....eacock.jpg

    Regards,
    Valerie

  46. Invasion of the peacocks (video on right side of page):

    http://www.cbsnews.com/stories.....age2.shtml

  47. Valerie (comment #30):”Phillip Johnson proposed the “magical storybook designer”, not me. Look again at the Johnson quote from earlier in the thread… He is saying that peacock tails are “life-threatening decorations” that natural selection never would have produced, but just the kind of goofy thing that a whimsical creator might produce.”

    Actually, it wasn’t Johnson, it was Douglas Futuyma who brought up the Creator with regard to the peacock. The Johnson quote was not complete. With previously intentionally omitted material included, the quote reads:

    “…what I find intriguing is that Darwinists are not troubled by the unfitness of the peahen’s sexual taste. Why would natural selection, which supposedly formed all birds from lowly predecessors, produce a species whose females lust for males with life-threatening decorations? The peahen ought to have developed a preference for males with sharp talons or mighty wings. Perhaps the taste for fans is associated genetically with some absolutely vital trait like strong egg shells, but then why and how did natural selection encourage such an absurd genetic linkage? Nevertheless, Douglas Futuyma boldly proclaims the peacock as a problem not for Darwinists but for creationists: ‘Do the creation scientists really suppose their Creator saw fit to create a bird that couldn’t reproduce without six feet of bulky feathers that make it easy prey for leopards?’ I don’t know what creation-scientists may suppose, but it seems to me that the peacock and peahen are just the kind of creatures a whimsical Creator might favor, but that an ‘uncaring mechanical process’ like natural selection would never permit to develop.” Phillip Johnson, Darwin on Trial, pp. 30-31.

    I apologize for forgetting to add ellipses. (I wasn’t trying to hide anything — the stuff about genetic linkage just seemed a silly digression to me.)

    taciturnus (comment #32): “It seems like anything at all could be explained by this method.”

    From Darwin’s Origin: “Sexual Selection… depends not on a struggle for existence… but on a struggle between the individuals of one sex, generally the males, for the possession of the other sex. The result is not death to the unsuccessful competitor, but few or no offspring… Generally, the most vigorous males…will leave most progeny. But in many cases, victory depends not so much on general vigor, as on having special weapons, confined to the male sex. A hornless stag or a spurless cock would have a poor chance of leaving numerous offspring…male salmons have been observed fighting all day long; male stag beetles sometimes bear wounds from the huge mandibles of other males… Amongst birds, the contest is often of a more peaceful character…singing…gorgeous plumage…”

    From R.A. Fisher’s Genetical Theory of Natural Selection, p. 136: “…the modification of the plumage character in the cock proceeds under two selective influences (i) an initial advantage not due to sexual preference, which advantage may be quite inconsiderable in magnitude, and (ii) an additional advantage conferred by female preference. The intensity of the preference will itself be increased by selection so long as the sons of hens exercising the preference most decidedly have any advantage over the sons of other hens, whether this be due to the first or to the second cause.”

    I would say that it seems that it might be invoked for any exaggerated trait indicative of health that (typically) males happened to have. In any case, it doesn’t explain the generation of novel cell types, tissue types, organs, or body plans (credit: ds).

    valerie (comment #33): “it remains true that the Fisherian mechanism can explain the aftermath, provided that an initial preference for brightness arises by any mechanism at all.”

    Depending on the species, it could also explain darkness, featherlessness, big feet, little feet, long legs, short legs, skinny legs, fat legs, etc. It seems that this could very quickly get completely out of control, and that species with any substantial tendency to engage in it probably are probably headed toward extinction.

  48. j wrote:
    “Actually, it wasn’t Johnson, it was Douglas Futuyma who brought up the Creator with regard to the peacock. The Johnson quote was not complete.”

    Hi J,
    Futuyma brings up the Creator because he *doesn’t* think a Creator could be responsible for the peacock, suboptimal as it is. Johnson is the one who suggests that a “whimsical Creator” could have made the peacock, but that selection would have produced something different.

    Interestingly, though writing the book in 1991, Johnson demonstrates apparent ignorance of sexual selection theory, despite the fact that the idea was introduced by Darwin himself and developed by Fisher around 1930.

    taciturnus (comment #32): “It seems like anything at all could be explained by this method.”

    Not quite anything — it has to be a trait that 1) has been exaggerated beyond the point of maximum survival value, and 2) is preferred by the ‘choosy’ sex when making mating decisions.

    “I would say that it seems that it might be invoked for any exaggerated trait indicative of health that (typically) males happened to have.”

    I think that’s right.

    “In any case, it doesn’t explain the generation of novel cell types, tissue types, organs, or body plans (credit: ds).”

    I *knew* I’d heard that somewhere before. :-)

    “Depending on the species, it could also explain darkness, featherlessness, big feet, little feet, long legs, short legs, skinny legs, fat legs, etc.”

    It does explain a huge variety of traits in nature, including:

    a) the number of songs in a grackle’s repertoire
    b) “sword” size in swordtail fish
    c) elaborate courtship dances
    d) the length of eye stalks in stalk-eyed flies (amazingly, they can be as long as the fly’s body)
    e) crests on birds
    f) air sacs in sage grouse
    g) acrobatic courtship displays in long-tailed manakins

    These are not speculative, by the way. They have all been shown to have a strong influence on female mating choices.

    I’m glad you mentioned the variety and the arbitrariness of “ornaments”, because it reminded me that sexual selection is thought by some to accelerate speciation. According to this idea, a couple of separated subpopulations of a species may develop different ornaments. The differences are initially subtle, but get magnified rapidly by the Fisherian feedback loop. Once the ornaments diverge sufficiently, females of one of the subpopulations will no longer be attracted to males of the other. Reproductive isolation is thus achieved, and the now separate groups continue to diverge, forming separate species.

    “It seems that this could very quickly get completely out of control, and that species with any substantial tendency to engage in it probably are probably headed toward extinction.”

    Fortunately for those species, it’s a self-limiting phenomenon. The exaggeration of the trait in question stops when any further increase in reproductive success is exactly offset by the decrease in survivability. The equilibrium point may shift with environmental conditions, but you never get a full-blown, open-ended runaway.

    Valerie

  49. Valerie,

    Thank you for your clarifications and I think I might be close to understanding the argument. The part that still bothers me is this:

    “An initial correlation between feather brightness/size and health in the original, modest-looking population ignited a Fisherian feedback loop that led to the current absurd situation.”

    I’m still bothered by that “initial correlation.” In the original drab population, was it normal for healthy birds to have drab feathers or, even in the original population, were the healthiest birds also the ones with the brightest feathers? I’ve been thinking of the original population as having the following characteristics:

    1. Peacocks are on average drab. Healthy peacocks typically have feathers of normal drabness (but not always.)

    2. Peahens sexually select for the normal drab feathers of this population. (If they already sexually select for bright feathers, then we are assuming what needs to be explained.)

    Then we hypothesize the following: A peacock, or number of peacocks, with extraordinary health are born who also have extraordinarily bright or showy feathers. At this point, this is just a coincidence. These peacocks are more prone to predation but survive better, on average, due to their health. The coincidence “breaks the lock” on the sexual selection for drab feathers and relocks it on bright feathers, which then feeds back on itself and eventually produces the extremely bright and showy feathers we find in peacocks today. Also, the bright and showy peacocks also become on average the healthier ones because bright and showy feathers become normal for the population, which explains why health and showy feathers are strongly correlated in contemporary populations.

    Am I understanding things correctly?

    Dave T.

  50. avocationist: “Peacocks have been kept as tame birds in India for over 3000 years. I suspect that peacock features may have been accentuated by human preference.”

    valerie: “You might be right.”

    “…it seems to me that the peacock and peahen are just the kind of creatures a whimsical Creator might favor…” Johnson was on the right track.

    valerie: “Futuyma brings up the Creator…”

    Note that that is yet another example of an NDEist arguing about theology.

  51. “From the peahen’s conscious perspective, she is just following her instinctive sexual urge, nothing else. Her genes, on the other hand, are “using” her libido to get themselves reproduced. By creating a preference for long-tailed males, they improve their success. The peahen is unaware of what her genes are trying to do, of course, and simply feels more desire for a long-tailed male.”
    This is how it sounds to me:
    ‘Evolution is the result of genes. Genes are the result of evolution.’

    Quite frankly, it’s a bit of ‘clank.’
    Here’s how you put it:
    “ The desires are instinctual, but they serve an evolutionary rationale, because, after all, they are shaped by evolution.” Clankity-clank.
    You wrote: “But don’t you see the appeal of a theory which successfully explains *why* things are that way, rather than simply noting the facts and shrugging?”
    But Valerie, I like theories that are correct and that can lead me forward, not jus theories “which ‘successfully’ explains why things are the way they are”. The Ptolomeic version of planetary motion is almost identical with the Copernican. It ‘successfully’ explained what was going on. It just simply happened to be completely wrong. I see a parallel here.
    You wrote: “And given that you are an ID supporter who doubts selection, would you then say that peafowl are the way they are because the designer made them that way? If so, it raises the question, why would he have done so in precisely the way that mimics the predictions of sexual selection theory? Isn’t it a “just-so story” to say that peafowl (and a huge number of other species) were designed in a way that just happens to correspond to the predictions of sexual selection theory?”

    You say I have ‘doubts’ about selection. In an earlier post, I suggested that it would be better to call the ‘work’ of NS “adaptation.” Yes, there’s a ‘selective’ element to the ‘work’ of ‘adaptation’; but the ‘selective’ force we see is simply ‘used’, if you will, by the animal to ‘adapt’ to the particular environment. In other words, what’s primary is not ‘selection’, but the ‘adaptability’ of the animal. Or, to put it another way again, the animal ‘uses’ ‘selection’ to ‘adapt’, rather than ‘selection’ using the animal’s ‘adaptability.’ Darwinists see NS as the primary, all-powerful force, active in Nature. I’m beginning to sense that the ‘all-powerful’ force at work is the organisms’ ability to switch gear, so to speak: it uses Nature to define its being, rather than Nature imposing upon it its being.

    It has the additional benefit of easily distinguishing micro- from macro-evolution, and transmitting the correct idea of the limited scope of what’s happening.

    When you say: “Isn’t it a “just-so story” to say that peafowl (and a huge number of other species) were designed in a way that just happens to correspond to the predictions of sexual selection theory?”, again, I hear all of this in a completely different (opposite) way. So I would ask: Isn’t taking the mechanisms that we find already evident in Nature, and then applying a putative theory that cannot be proven, i.e., ‘sexual selection’, and saying that that’s how Nature came about, only making up a “just-so story”?

    As I said before, we just seem to be talking past each other.

    Onwards.

  52. taciturnus wrote:
    “Thank you for your clarifications and I think I might be close to understanding the argument.”

    Hi Dave,
    I think we’re getting close. I apologize if my explanations haven’t been very clear.

    “In the original drab population, was it normal for healthy birds to have drab feathers or, even in the original population, were the healthiest birds also the ones with the brightest feathers?”

    Both. Let me offer a hypothetical example to illustrate why.

    Imagine we have an original population of dull black birds. Their plumage ranges from matte black to a just slightly glossy black. Further suppose that the slight glossiness is due to a little bit of oil which these birds produce but which the other birds lack, and that the oil repels water and fends off hypothermia in cold, wet weather. All of these birds are hopelessly drab compared to a peacock or a bird of paradise, but the glossiest birds nevertheless have a small survival advantage due to the oil.

    Females who randomly develop a preference for glossy males will tend to produce glossy offspring who will survive better in cold, wet conditions. The preference for glossiness will therefore spread throughout the female population. Once the preference is well established, the Fisherian feedback cycle will kick in and the males will become glossier and glossier in order to attract females. At some point the males may “invent” other ways of triggering the females’ glossiness detectors, say by adding color. In any case, the males are forced to evolve showier plumage in a race to stay ahead of the other males.

    So far, all of this assumes that the female preference is open-ended. In other words, ‘glossier is better’ to the females. You might ask, why do the females develop an open-ended preference? Too much oil, for example, would be a bad thing. So why don’t the females develop a preference for males who are glossy, but not *too* glossy?

    The answer is that in the original population, even the glossiest birds are not too glossy. In other words, the Aristotelian mean of glossiness is well above the actual range of glossiness found in the population. Since the females are never exposed to males who are too glossy, they have no opportunity to develop a tuned preference for ‘optimum’ glossiness. Glossy is always better in their world, so they develop an open-ended preference. This open-ended preference is what drives the Fisherian mechanism.

    To restate things in the abstract, here’s what it takes to activate Fisher’s mechanism:
    1. An original population with a varying characteristic ‘C’.
    2. A monotonic correlation between C and health/survivability. In other words, either more of C is always better, or less of C is always better, within the range of C actually found in the population.
    3. The ability in the ‘choosy’ sex to ‘measure’ C.

    If those conditions obtain, the choosy sex will tend to evolve a preference for mates having the most (or least) of characteristic C. The males will amplify (or diminish) C in order to keep the females interested, and the feedback cycle is in full swing.

    I hope that helps.

    Regards,
    Valerie

  53. avocationist wrote:
    “Peacocks have been kept as tame birds in India for over 3000 years. I suspect that peacock features may have been accentuated by human preference.”

    I wrote:
    “You might be right.”

    j wrote, quoting Johnson:
    ““…it seems to me that the peacock and peahen are just the kind of creatures a whimsical Creator might favor…” Johnson was on the right track.”

    j,
    I don’t follow your reasoning. Could you explain why you think “Johnson was on the right track”?

    j writes:
    “Note that [Futuyma's comment] is yet another example of an NDEist arguing about theology.”

    Not because Futuyma has strong ideas about what the Creator must be like. After all, Futuyma is an evolutionist who does not think that the diversity of life on Earth requires a Creator. Futuyma just wants creationists to confront the implications that the peacock has for the motivations and/or abilities of the Creator, if he exists. Most creationists envision an omnipotent Creator who produces beautiful, elegant designs. They become uncomfortable when nature’s flaws are pointed out to them.

    Interestingly, some Christian creationists avoid the problem by assuming that any imperfections in Nature are the result of the Fall, but this raises other questions, like “Did peacocks truly get their tails only *after* the Fall?”

    Valerie

  54. PaV wrote:
    “This is how it sounds to me:
    ‘Evolution is the result of genes. Genes are the result of evolution.’”

    Evolution is not the result of genes, but of *changes* to genes. A better sound bite would be “old genes plus changes to genes, filtered through natural selection, equals new genes.”

    “Here’s how you [Valerie] put it: ‘The desires are instinctual, but they serve an evolutionary rationale, because, after all, they are shaped by evolution.’ Clankity-clank.”

    Onomatopoeia is fine, but do you have an actual *reason* for rejecting my statement? Could you share it with the rest of us?

    “The Ptolomeic version of planetary motion is almost identical with the Copernican. It ‘successfully’ explained what was going on. It just simply happened to be completely wrong.”

    Not true. The Ptolemaic system did *not* explain why Venus and Mercury go through a full set of phases (like the Moon). The Copernican system did. This was a clear reason to prefer the Copernican model, and many more reasons have accumulated since then.

    Let’s compare theories.

    Sexual selection is falsifiable and predicts all of the following:

    1. Males tend to be showy, and females choosy, except in species where males invest more in raising the young than the females do.

    2. The most elaborate “ornamentation” is found on the side that does the courting, not on the side that does the choosing.

    3. Extreme ornaments, such as peacock tails, are maintained despite the cost in survivability to their owners.

    4. In species where those extreme ornaments exist, the opposite sex prefers mates with the most elaborate ornaments.

    5. Natural selection will limit the degree to which ornaments are exaggerated.

    6. The ornaments may be radically different between closely related species.

    You are offering a theory which explains none of these, yet you claim we should prefer your theory to the theory of sexual selection. On what basis?

    You wrote:
    “I like theories that are correct and that can lead me forward…”

    But how can you determine if a theory is correct, except by comparing its predictions to the data? And as for leading us forward, sexual selection theory has been tremendously productive in inspiring new research questions. One of the most intriguing is whether the explosion in brain size during hominid evolution was in fact due to sexual selection.

    “Isn’t taking the mechanisms that we find already evident in Nature, and then applying a putative theory that cannot be proven, i.e., ‘sexual selection’, and saying that that’s how Nature came about, only making up a “just-so story”?”

    First of all, scientific theories can never be proved, only disproved. Successful theories are the ones that remain standing when their competitors have been falsified.

    Secondly, just-so stories have no predictive power. Sexual selection theory predicts all of the things I listed above and matches the evidence. How can you, with a straight face, call sexual selection a just-so story?

  55. Valerie,

    Yes, that does help, but you didn’t say anything about my condition #2 of the original population, which is that the peahens in the original population were sexually selecting for the normal, drab peacocks. We have two alternatives to this possibility:

    1. The peahens were selecting for showy peacocks in the original population. In this case, we haven’t explained anything, since the thing we are supposed to be explaining is why peahens choose showy peacocks at all.

    2. Peahens were not sexually selecting at all in the original population. In this case, we need to explain the origin of sexual selection altogether, and why peahens started sexually selecting at all.

    So it makes sense to presume that in the original population, the peahens were sexually selecting for the ordinary, drab peahens. Then some peacocks came along who had glossier feathers, making them healthier, and the peahen sexual selection was “broken” and reestablished on glossy feathers. Then the feathers got glossier and glossier, showier and showier, even to the point that they were detrimental to the survivability of the males, because the females are locked on to showy feathers and the males are in an “arms race” to get the showiest feathers.

    The difficulties I have with this scenario are:

    1. If “healthier” peacocks can break the sexual selection lock and reestablish it on a new trait, why don’t the healthier peacocks in the later populations break the lock on showy feathers and reestablish it on a healthier or more survivable trait? Why can’t a drabber but healthier peacock break the lock on showy feathers and reestablish it in the other direction? Our scenario supposes that the selection lock was broken once and only once, and is ever after unbreakable no matter how detrimental the chosen characteristic becomes. This seems to me to be an explanation by coincidence. Wasn’t the original population itself an outcome of a Fisherian cycle?

    2. The showy peacock feathers in current populations are a paradox because they seem to have nothing directly to do with health and seem positively detrimental to survivability. To solve the paradox, we suppose that there was an original population of peacocks with drab feathers in which “glossy” feathers gave an advantage in survivability, maybe because they offered better thermal protection. In other words, we make a positive link between survivability and showy feathers in the original population. Once this link is made (whereever it is made) the paradox disappears… and the link is made just at the point where no empirical evidence could disprove it. What we have done is explain a paradox in an observable population by positing an original, unobservable population that did not have the paradox. Is there any reason for supposing this original peacock population, drab but with a few birds with healthy, glossy feathers, actually existed? If there is, then we have a genuine scientific hypothesis. If our only empirical reason for supposing it is that we need it to explain current populations, then what we have is a textbook “just-so” story. That is why I keep harping on the link between health (survivability) and showy feathers in the original population… if we make this link in the original population merely to explain the paradox that they are not linked in current populations, the only thing we have done is removed the paradox to a population we can’t observe and made it disappear by fiat.

    You’ve asked me to provide an alternate theory. My own opinion is that there are many questions that might simply be unanswerable, their answers lost in the mists of time. The danger with such unanswerable questions is not in leaving them unanswered, but thinking we have answered them when we haven’t. Why do peacocks have showy feathers? I really don’t know, and I suspect no one else really does either. If you want to suppose a whimsical Creator, you are free to do so. We can also speculate a series of natural coincidences stretching back beyond observable history to explain it. Maybe it happened that way, and maybe it didn’t. No one really knows….

    Cheers,
    Dave T.

  56. Valerie,

    Reading your last comment to PaV about the predictions made by sexual selection theory… is sexual selection theory an explanation of currently observable phenomena, an explanation of origins, or both? I have no problem with sexual selection theory as an explanation of currently observable phenomena. The empirical phenomena numbers 1 through 6 you listed in the post to PaV seem to be explainable by sexual selection. Peahens DO in fact choose peacocks with the showiest feathers even if those males are not the most survivable. In this sense, I think the theory is interesting and useful. But empirical facts 1 through 6 are evidence about how sexual selection maintains current population characteristics, not how it originates new ones.

    What I have problems with is sexual selection as a theory of origins. It is a different question from the question of currently observable phenomena. That sexual selection explains why showy peacocks stay around in current populations is one thing, explaining how peahens came to prefer showy peacocks to drab ones in the first place is an entirely different question. The only possible way to do the latter (from an evolutionary perspective) is to somehow demonstrate a link between showy feathers and survivability somewhere along the historical line. We’ve done this by speculating a survival advantage to oily, glossy feathers in the original population. But without independent empirical support for this speculation, all we have done is suppose as a matter of fact what our theory demands as a matter of logic. The same point goes for our assumption that the sexual selection lock was broken once in the original population and never again.

    Cheers,
    Dave T.

  57. valerie: “I don’t follow your reasoning. Could you explain why you think ‘Johnson was on the right track’?”

    His intuition was probably correct — that the spectacular nature of the peacock’s plumage is reflective (to a degree at least) of the work of a whimsical intelligence. He suggested it might be God; it looks like its man and woman. avocationist independently intuited something similar. There’s just something about it that says “not totally natural.” This lead to her discovery that tame peacocks have been kept for at least 3000 years in India. I bet it’s been much longer than that. People like those decorations, too. I think that there’s no way that such a creature would not have been artificially selected — consciously or unconsciously — for fortuitous breeding during its lengthy tenure as a tame animal, and that some of those tame animals would have found there way back into the wild. This is not to say that that’s the case with all instances of exaggerated features attributed to SS, just that in this particular case, the gratuitous materialist demand that it must be the result of non-intelligent causes appears to have led to a wrong conclusion.

    Compared to the peacock, those “never been domesticated” examples of SS that you linked to in comment #45 are pretty unimpressive.

    valerie: “Futuyma just wants creationists to confront the implications that the peacock has for the motivations and/or abilities of the Creator, if he exists. …some Christian creationists avoid the problem by assuming that any imperfections in Nature are the result of the Fall, but this raises other questions, like ‘Did peacocks truly get their tails only *after* the Fall?’ ”

    I’ve never understood that assertion. To me, it’s clear from reading Genesis that the Fall was a human spiritual event, with (intellectual) consequences only for humans. (“knowing good from evil”, “you will give birth to your children in pain”, “Painfully you will get your food from [the soil].”) (The snake is strictly a stand-in for the Devil.)

    But we don’t know enough to decide whether there are “imperfections” in nature. Without knowing the constraints on, or goals for, the design of nature, speculating about whether something could have been “better” than it is, is futile. Also, things may have artistic or “literary” purposes…

    Also, a while back, you had said, “Johnson demonstrates apparent ignorance of sexual selection theory” However, from reading Darwin on Trial, it’s clear to me that he’s awfully well-read and knowledgeable about all the major apects of the theory of evolution, including SS.

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