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Homology and Homoplasy

In the response to a recent post a commenter asks what “homologous” means and whether similarity is the same as homology.  In this post I will give a brief (and hopefully plain language) overview of “homology” and the related concept of “homoplasy.”

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Here is the standard Neo-Darwinian explanation of homology and homoplasy: 

Suppose two organisms have a similar feature.  The features are “homologous” if they were inherited by the organisms from a similar feature in a common ancestor.  In other words, the features are homologous if they result from a shared genetic ancestry.  Bat wings and human arms are homologous because they are similar structures inherited from a shared mammalian ancestor.   

On the other hand, the features are not homologous, but “homoplasious” if they were not inherited by the organisms from a similar feature in a common ancestor.  In other words, the features are homoplasious if they did not result from a shared genetic ancestry.  Homoplasious structures evolved independently more than once in a process known as convergent evolution.  Bird wings and insect wings are homoplasious; they are similar and perform the same function, but they do not result from common genetic ancestry.  Homoplasious features are also called “analogous features.” 

The difficulty is determining whether similar structures are homologous or homoplasious, because similarity, does not necessarily imply common ancestry.  As Gavin De Beer points out: 

“Homologous structures need not be controlled by identical genes, and homology of phenotypes does not imply similarity of genotypes.”  Gavin De Beer, Homology, an Unsolved Problem (London: Oxford University Press, 1971), 16. 

Roger Lewin adds:  “The key issue is the ability correctly to infer a genetic relationship between two species on the basis of a similarity in appearance, at gross and detailed levels of anatomy.  Sometimes this approach . . . can be deceptive, partly because similarity does not necessarily imply an identical genetic heritage:  a shark (which is a fish) and a porpoise (which is a mammal) look similar.”  Roger Lewin, Bones of Contention: Controversies in the Search for Human Origins (New York: Simon and Schuster, 1987), 123. 

Scientists attempt to determine homology through “outgroup comparisons.”  An “outgroup” is a group of organisms (a taxon) that diverged from two other groups (taxa) before they diverged from one another.  In other words, two of the taxa are more closely related to each other than they are to the third group, because they share a common ancestor with each other that they do not share with the outgroup.  The more closely related groups are called the “ingroup.”  Outgroup organisms are thus near relatives of ingroup organisms but not part of the ingroup. 

Researchers use outgroup comparisons to determine the “polarity” (that is the direction) of evolution.  Because the ingroup branched off from the common ancestor after the outgroup, scientists can assume that any character the ingroup shares with the outgroup must have been inherited from the ingroup’s common ancestor.  In other words, a character state that is present in both the outgroup and the ingroup is ancestral, and a character state that is in the ingroup only is not ancestral but derived. 

Now the problem with using homology to show common ancestry is that it is quite circular.  Jonathan Wells points this out: 

“Many biology textbooks define homology as similarity due to common ancestry, yet claim that it is evidence for common ancestry.  For example, Starr and Taggart’s Biology: The Unity and Diversity of Life (8th Edition, 1998) states that the “pattern of macroevolution–that is, change from the form of a common ancestor–is called morphological divergence…. Homology [is] a similarity in one or more body parts in different organisms that share a common ancestor…. Homologous structures provide very strong evidence of morphological divergence.” (pp. 318-319)  In a section on “The Evidence for Evolution” in the teacher’s edition of Johnson’s Biology: Visualizing Life (1998), students are told that “homologous structures are structures that share a common ancestor,” and an accompanying note tells the teacher that “such structures point to a common ancestry.” (p. 178)  According to Campbell, Reece and Mitchell’s Biology (5th Edition, 1999), “similarity in characteristics resulting from common ancestry is known as homology, and such anatomical signs of evolution are called homologous structures. Comparative anatomy is consistent with all other evidence in testifying [to] evolution.” (p. 424) Raven and Johnson’s Biology (5th Edition, 1999), in a section titled “The evidence for macroevolution is extensive,” includes the following: “Homology: Many organisms exhibit organs that are similar in structure to those in a recent common ancestor. This is evidence of evolutionary relatedness.” A few pages later, the same textbook explicitly defines homologous structures as “structures with different appearances and functions that all derived from the same body part in a common ancestor.” (pp. 412, 416) Audesirk, Audesirk and Byers’s Life On Earth (2nd Edition, 2000) calls homology “evidence of relatedness” in a section titled “Comparative Anatomy Provides Structural Evidence of Evolution.” The textbook tells students: “Internally similar structures are called homologous structures, meaning that they have the same evolutionary origin despite possible differences in function. Studies of comparative anatomy have long been used to determine the relationships among organisms, on the grounds that the more similar the internal structures of two species, the more closely related the species must be, that is, the more recently they must have diverged from a common ancestor.” (p. 236)”

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38 Responses to Homology and Homoplasy

  1. 1
    Reciprocating Bill

    Bring on the “Poof” model!

  2. Okay.

    POOF! You’re now in the moderation sandbox.

  3. 3
    Reciprocating Bill

    Mine was a serious comment. Your ID choices are descent with meddling, or repeated “poofs.” Since BarryA would like to doubt descent, he is left with “poof.” Show me where I am wrong.

  4. See ISCID Encyclopedia http://www.iscid.org/encyclopedia/Sequelog

    Sequelog

    The term ‘sequelog’ denotes a nucleotide or amino acid
    sequence that is similar, to a specified extent, to another
    sequence. This term is strictly about sequential similarity and implies nothing about evolutionary relatedness and functional properties of sequences.

    Defined by Alexander Varshavsky

    See also: homolog, ortholog, paralog, pseudoortholog, pseudoparalog, spalog, xenolog
    —————–
    Spalog http://www.iscid.org/encyclopedia/Spalog

    The term ‘spalog’ (pronounced [spailog]) denotes a 3-D structure that is spatially similar, to a specified extent, to another 3-D structure. This term is strictly about spatial similarity and implies nothing about evolutionary relatedness and functional properties of structures.

    Defined by Alexander Varshavsky

    See also: homolog, ortholog, paralog, pseudoortholog, pseudoparalog, sequelog, xenolog

    Web Resources On Spalog

    The trouble with homology
    Orthologs, Paralogs and Evolutionary Genomics
    CV of Alexander Varshavsky

  5. “Show me where I am wrong.”

    Okay again.

    The third option, and the one I have settled on as the best explanation, is front loading. The first life on earth was designed to diversify according to a plan and needed no assistance along the way. Consider a fertilized human egg cell. It is front loaded with all the information it needs to diversify into myriad cell types, tissue types, and organ types that compose a human being. Nothing is left to chance in this process formally called ontogenesis. I posit that phylogenesis is the same process on a different scale with nothing left to chance. This of course prompts the question of where the phylogenetic stem cell (my term for the common ancestor of all life on this planet) came from. Granted that’s a hard question and it may not be answerable but it isn’t the only such hard question. The question of where matter and energy came from (the origin of the observable universe) is even harder. Still we struggle to explain what we can even when the trail of evidence leads to a brick wall we cannot see through, over, or around.

  6. Reciprocating Bill,

    I’m curious. I have never expressed an opinion regarding common descent on this blog. Upon what evidence is your pronouncement in 3 based?

  7. Reciprocating Bill,

    Tell me how any naturalistic explanation of evolution that tries to fit the data isn’t also based on a “poof” model. Somehow each major taxon or novel body part or function magically appeared at some time in the distant past without an obvious predecessor.

    That what the whole argument is about, our “poof” models versus their “poof” models. Let the students decide which “poof” makes the most sense.

  8. Barry A:
    In the response to a recent post a commenter asks what “homologous” means and whether similarity is the same as homology.

    It was the hobbit leaf that made me do it!

    But thank you for the post it demonstrates the subjective-ness/ specious argument of Nick Matzke’s post on PT.

    As for the “poof” model- if that is what the data leads us to then so-be-it. IOW if it is demonstrated that the level of change required for any CD model is not capable via any method then what options are left?

  9. DaveScot,

    The front loading scheme is very interesting, however I’m curious if you think the front loading is fully contained in the organism, or is it in the Universe itself? The initial problem I see with organism only, is that the front loading couldn’t simply be a series of progressive steps that get turned on later, but instead it would have to be branches upon branches upon branches of possible steps that get turned on depending on the environmental factors. So an example would be the common ancestor of all reptiles, birds and mammals. It would have to have the front loading information for all those branches that reach to the descendents of today and the front loading for any possible future branches. Also, that’s only taking into account the branches for the species that were actualized, what about the possible branches that were never actualized?

    If the Universe itself can contain the front loading information, then something like the supposed meteor that wiped the Dinosaurs could be seen as a front loaded element that helped the mammals along. The problem I see with this, is that this front loaded Universe would look exactly like a Universe that wasn’t front loaded. (basically determinism vs non) At this point it just depends on what philisophical icing you’d like to spread on your grasp of reality and science has no say on front loading vs. non.

  10. DaveScott, you may be amused to know that your ideas are similar in at least one respect to YEC’s. They know Noah’s ark was much too small to hold all the critters we see around us today. They deal with this problem by positing that Noah loaded up the arc with front loaded “types.” Noah did not have tigers and lions and cheetahs and bobcats and pumas and housecats, etc. He had only one front loaded “cat” type from which all other cats descended.

    Joseph, we in the BarryA household take our hobbits very seriously. My spousal unit has read the Ring series 39 times at the latest count (only twice for me). We amuse ourselves playing Rings trivial pursuit. Naturally, I am soundly thrashed every time.

  11. BarryA, I take the hobbit leaf very seriously :) and you should read “Noah’s Ark: A Feasibility Study” by Woodmorappe. According to him Noah had up to the genus level of today’s organisms on the Ark. Felidae is the family but that is divided into two subfamilies of which there are 14 genera. IOW according to the YECs Noah would have had at least 28 “cats” on board- FYI.

  12. 12

    DaveScott said: “The third option, and the one I have settled on as the best explanation, is front loading.”

    Front loading, if I read you correctly, still yields a picture of common descent and branching radiation of organisms characterized by sometimes homologous, sometimes analogous similarities – driven by a mechanism other than natural selection. Objections to seeing homology as grounded in common descent, as implied by this post, are as problematic for your model as it would be for orthodox evoluationary theory, if they had any force at all.

    BarryA said: “I’m curious. I have never expressed an opinion regarding common descent on this blog. Upon what evidence is your pronouncement in 3 based?”

    Your comment, “Now the problem with using homology to show common ancestry is that it is quite circular” suggests doubt regarding common descent. If I got it wrong, why not declare your thoughts on the topic?

    Jerry said: “That what the whole argument is about, our “poof” models versus their “poof” models.

    You miss important distinctions. If you reject common descent, and instead postulate sudden appearance, the first instance of each species must “poof” into existence somewhere, followed by ordinary reproduction of unchanged descendents. OTOH, an ID model that suggests the subtle, periodic infusion of “new information” into the arrangement of DNA of descendant organisms does not have that problem. Neither does descent with modification by means of natural selection. I recommend Howard Van Till’s interesting argument regarding the “mind like” versus “hand like” phases of design implied by the intelligent design hypothesis. The latter (“hand like”) phase of design is utterly neglected by ID as a result of the studied, agnosticism of the ID camp regarding the nature of the designer or designers, the process of design, and ultimately the means by which matter and energy are arranged (with little tweezers?) in such a way to physically instantiate design.

  13. Joseph, the YEC’s I have read have only the family level on the ark. You have to admit, having just two cats would have made the ark a lot roomier.

  14. Reciprocating Bill:

    You left out the most important choice: “I don’t know”. What we have is a pattern of data that does not lend itself to any coherent naturalistic explanation (yet). You can do what seems to be the normal practice of grant-grubbing scientists these days (draw a stright line through as many of the points as you can, erase the others, and hope no one reads your notes too closely), or you can simply leave it as an open problem. We have no plausible naturalistic explanation for how the universe came to be, either, and yet the edifice of science seems to survive just fine. Scientific theories don’t get to “win” by default.

  15. you should read “Noah’s Ark: A Feasibility Study” by Woodmorappe. According to him Noah had up to the genus level of today’s organisms on the Ark.

    Isn’t that the guy that used the median rather than the mean body size to calculate how many animals could fit on the ark? I don’t really see the point of advocating for young earth Creationism here, as it has nothing to do with ID, and I doubt there are more than a couple YECs hanging around here. It only makes it clearer that you are parodying the ID position when you argue for YEC/deny common descent with the most obviously bizarre assertions.

  16. Fross wrote: “The problem I see with this, is that this front loaded Universe would look exactly like a Universe that wasn’t front loaded.”

    But wouldn’t a NDE universe have extraneous DNA left over from previous species while a Front Loaded universe have it from species yet to come? Either way it would seem that both hinge on the existence of junk DNA.

  17. HodorH:
    Isn’t that the guy that used the median rather than the mean body size to calculate how many animals could fit on the ark?

    Perhaps you could provide a reference and then we will see if that really matters.

    HodorH:
    I don’t really see the point of advocating for young earth Creationism here, as it has nothing to do with ID, and I doubt there are more than a couple YECs hanging around here.

    Iwasn’t advocating anything. I was just making a point.

    HodorH:
    It only makes it clearer that you are parodying the ID position when you argue for YEC/deny common descent with the most obviously bizarre assertions.

    Actually YOUR posts make it clear that you cannot separate the two regardless of reality and common descent is a bizarre assertion- especially given what we do know.

  18. HodorH,

    Neither I nor Joseph was arguing for the YEC position. We were simply noting as a point of interest their position, which is, in some respects, consistent with the front loading hypothesis.

  19. Perhaps you could provide a reference and then we will see if that really matters.

    Tell you what. I’ll give you a reference if you can tell me why it matters whether one uses a median or mean.

    Actually YOUR posts make it clear that you cannot separate the two regardless of reality and common descent is a bizarre assertion- especially given what we do know.

    I’m having a little trouble parsing this one. I’ll replace that “and” with a period and go from there. For the first part, um, I’m an IDer who believes in common descent. For the second, since I’m pretty sure you’re a parody, I don’t suppose it would be worth my 5 minutes to argue this one with you.

  20. Hi BarryA

    DaveScott, you may be amused to know that your ideas are similar in at least one respect to YEC’s. They know Noah’s ark was much too small to hold all the critters we see around us today.

    Partially correct. According to the Book of Genesis, Noah took the basic “kinds” not every single species in existence at the time. And even from these, he only had to take the ones who breath through the nostrils, and only the land animals. Plenty of water outside, so no need to bring sea animals. ;-)

    They deal with this problem by positing that Noah loaded up the arc with front loaded “types.” Noah did not have tigers and lions and cheetahs and bobcats and pumas and housecats, etc. He had only one front loaded “cat” type from which all other cats descended.

    Pretty much. I would only exchange the word “type” for “kind”.

    Concerning the “Homology” issue it’s hard to understand why Darwinists still use this as “evidence” for evolution, when we now know that many of the so called “homologous” structures have totally diferent embryonic pathways, and are controled by diferent genes. As Dr Michael Denton puts it:

    “The validity of the evolutionary interpretation of homology would have been greatly strengthened if embryological and genetic research could have shown that homologous structures were specified by homologous genes and followed homologous patterns of embryological development. (…) But it has become clear that the principle cannot be extened in this way” – “Evolution: A Theory in Crisis” Michael Denton – page 145

    He then says

    “With the demise of any sort of straighforward explination for homology one of the major pillars of evolution theory has become so weakened that its value as evidence for evolution is greatly diminished” – ibid, page 151

  21. Perhaps you could provide a reference and then we will see if that really matters.

    HodorH:
    Tell you what.

    I take that as you have no intention of providing the reference.

    HodorH:
    I’ll give you a reference if you can tell me why it matters whether one uses a median or mean.

    It all depends on the context. Also in some cases the two could be the same, mean = median. But the context is the important thing. And that is why I asked for a reference. I have the book and I could easily look it up.

    Actually YOUR posts make it clear that you cannot separate the two regardless of reality and common descent is a bizarre assertion- especially given what we do know.

    HodorH:
    I’m having a little trouble parsing this one.

    I have no doubt about that.

    HodorH:
    For the first part, um, I’m an IDer who believes in common descent.

    If you are an IDist then you should know the differences between ID and Creation. And that should allow you to differentiate the discussion.

    HodorH:
    For the second, since I’m pretty sure you’re a parody, I don’t suppose it would be worth my 5 minutes to argue this one with you.

    It is obvious you can’t respond with anything of substance. All bluster no muster- what’s up with that?

    look at this again:

    HodorH:
    It only makes it clearer that you are parodying the ID position when you argue for YEC/deny common descent with the most obviously bizarre assertions.

    Just so we are clear (I am but obviously HH is not)- I was not arguing for YEC. I was clarifying a YEC point. That is it. I deny CD because it isn’t a scientific premise. It isn’t scientific because we do not yet know what makes an organism what it is. And in the absence of that knowledge ANY theory of CD is pure speculation.

  22. Source:
    Original Impact #273 : “A Resource for Answering the Critics of Noah’s Ark.” (ICR)

    To start out, I reviewed what Scripture actually teaches about what kinds of creatures were taken on the Ark in order to dispel the oft-repeated charge that the Ark needed to carry perhaps 50 million species of creatures. I then figured out how many animals were on the Ark, arriving at approximately 16,000. Since animals vary so much in size, a numerical figure itself is not too informative. Therefore, the 16,000 animals were assigned into body-weight categories. As a result, there were eight logarithmic categories spanning the hummingbird (a few grams each) and the largest dinosaur (nearly 100 tons when adult). Since most of the animals were small, the median animal on the Ark was about the size of a rat.

    and

    Because there have been so many arguments which allege the impossibility of eight people caring for so many animals, I delved into actual manpower studies on the time required to care for a given number of animals under various conditions. It turns out that simple labor-saving techniques could have enabled eight people to care for 16,000 rat-sized animals assuming the availability of only rustic tools, along with a 10-hour day, 6-day week, with time to spare.

    There, now you have a context. Now I know you’ll tell me why using the median is or isn’t appropriate.

    Just so we are clear (I am but obviously HH is not)-

    I’m not clear? Which of my statements are you having a hard time understanding?

    It isn’t scientific because we do not yet know what makes an organism what it is.

    You’ve said this many times, but I sure don’t know what you mean by it. I would interpret that as “we don’t know everything there is to know about an organism, so we can’t know anything about its ancestry.” It’s statements like these that make it look like you’re just trying to make IDers look bad. Perhaps you should clarify (prediction – Joseph will say something like “It’s OBVIOUS what I mean, you’re just too dumb to figure it out).

    And in the absence of that knowledge ANY theory of CD is pure speculation.

    So paternity testing is out?

    And as for me differentiating the discussion between ID and creationism, that’s hardly the point. What matters is what strangers to the subject will get from a visit to Uncommon Descent. I know and you know that ID is the set complement to chance and regularity. But the visitor will have to spend a long time here to figure that out, what with all the discussion of Dobzhansky’s religion, expanding universes, the relationship of Darwin to Hitler, etc.

  23. Homology… much still up for debate.

    Online textbook, Basics, Taxonomy, with “picture of embryonic development”, and example ‘homology’ of human, whale, and bat for an “opportunistic evolution.”
    http://users.rcn.com/jkimball......onomy.html
    So, because we see it in a textbook, it must be so.

    Green Tree of Life site sheds light on problems and proposals for plants: http://ucjeps.berkeley.edu/Tre.....posal4.php

    Yes, there were/are real problems…
    From Elizabeth Pennisi, “Is It Time to Uproot the Tree of Life?” Science, vol. 284, no. 5418, 21 May 1999, p. 1305,
    “A year ago, biologists looking over newly sequenced genomes from more than a dozen microorganisms thought these data might support the accepted plot lines of life’s early history. But what they saw confounded them. Comparisons of the genomes then available not only didn’t clarify the picture of how life’s major groupings evolved, they confused it. And now, with an additional eight microbial sequences in hand, the situation has gotten even more confusing…. Many evolutionary biologists had thought they could roughly see the beginnings of life’s three kingdoms… When full DNA sequences opened the way to comparing other kinds of genes, researchers expected that they would simply add detail to this tree. But “nothing could be further from the truth,” says Claire Fraser, head of The Institute for Genomic Research (TIGR) in Rockville, Maryland. Instead, the comparisons have yielded many versions of the tree of life that differ from the rRNA tree and conflict with each other as well…”

    It is admittedly dated, but shines light on problems past clearly unexpected by those in top positions. None of these people existed in a vaccuum.

    I would stop the madness of looking backwards and concentrate from an IDist perspective fully on living organisms, cross-platform experiments, transgenics, functionality., and Prophetic Genes*. An engineer works with functionality, controlling randomness. An engineer can use chaos, guide it, manipulate and anticipate based upon known environmental circumstances and required directed energy to overcome.

    Computer Power increase brings metagenomics, meta-analysis and supertrees into great perspective and can do the same for gene functionality and predictive powers.

    Looking at a Design paradigm, as an exercise, blow the known tree away and build from scratch based upon a genetic tree and function, to be “intentionally blind” to the past. Not because of any disrepect of past scientist, but because the current tree is one of the most confusing confabulations I’ve ever seen. And I’ve written and seen bad spaghetti code.

    The current nomanclature appears to be non-sensical and overwhelmed with classifications either to rudimentory or so overlapping as to make them utterly useless from a genetic perspective and certainly from any computational usage. There is so much noise that real information is still hidden even in what is currently known.

    Scientist from Texas Tech…
    http://www.bioone.org/perlserv.....8R2.1#N101
    title: SPECIATION IN MAMMALS AND THE GENETIC SPECIES CONCEPT, deals with morphology, biological species concept vs genetic species concepts. In 2006, this is still being fleshed out.

    Old homology nomenclature, was not the equivalent of a periodic table, upon which to build a base. Genetic trees are clearly still being established and its still a time of discovery. Building new trees from scratch and new datasets of classification can shed light where once only darkness prevailed due to vast assumptive logic on morphology alone.

    At times, an entire software rewrite is required in order that functional processes can contribute refined information and be more reliable to its endusers based upon latest knowledge base and technology. It appears to me the current classification system is unreliable for scientist as a Knowledge Accumulation Network because it ill affords order and contributes to confusion. Though there are fantastic new discoveries, the current classification system, based upon old paradigms, leads to database noise, not clarity.

    It appears to limit discovery, not allow it.

    In the days of IPOD, we need to reclassify bipods, tetrapods, swimapods and slinkapods with genetic information, but also with functionality, and Genetic Arrangement of Predictive mechanisms, or in short; Prophetic Genes, which establish known patterns in response to minimal and maximal coersion boundaries of environmental pressures such as; Climate, pressure, lack of food, one source of food, predatory habitats, etc., and any number of other environmental conditions.

    This is not just a matter of point mutations and deleterious byproducts. Nor are predictable patterns truly anticipated by the current neo-darwinian example. It is historical based.

    There appears to be for survival impact: functional change, semi-functional, non-functional, deleterious, and extinction. All appear to have boundary implications either in repair mechanisms, backups, abrupt death, or accepted range.

    *Fun with words, prophetic genes :) as opposed to Levi’s. Who woulda thunk in past times, $100 Levi jeans in Russia when we once paid $20 in America?

  24. It isn’t scientific because we do not yet know what makes an organism what it is.

    HodorH:
    You’ve said this many times, but I sure don’t know what you mean by it.

    What makes a fly a fly? In his book (English title) “Why is a Fly not a Horse?”, the prominent Italian geneticist Giuseppe Sermonti, tells us the following :

    Chapter VI “Why is a Fly not a horse?” (same as the book’s title)

    ”The scientist enjoys a privilege denied the theologian. To any question, even one central to his theories, he may reply “I’m sorry but I do not know.” This is the only honest answer to the question posed by the title of this chapter. We are fully aware of what makes a flower red rather than white, what it is that prevents a dwarf from growing taller, or what goes wrong in a paraplegic or a thalassemic. But the mystery of species eludes us, and we have made no progress beyond what we already have long known, namely, that a kitty is born because its mother was a she-cat that mated with a tom, and that a fly emerges as a fly larva from a fly egg.”

    And in the absence of that knowledge ANY theory of CD is pure speculation.

    HodorH:
    So paternity testing is out?

    It is if you are calling some unknown LUCA the parent of life’s diversity.

    HodorH:
    What matters is what strangers to the subject will get from a visit to Uncommon Descent.

    This is a blog. If someone has a question they should ask.

    (Thanks for the reference. But hold that for now…)

  25. And in the absence of that knowledge ANY theory of CD is pure speculation.

    Why?

  26. And in the absence of that knowledge ANY theory of CD is pure speculation.

    HodorH:
    Why?

    Because without that knowledge the premise cannot be objectively tested. Also without that knowledge no one, I repeat NO ONE, even knows if such changes* are even possible (*the changes required if all of life’s diversity owes its collective common ancestry to some unknown population(s) of single-celled organisms).

  27. Houston, we have a problem-

    HodorH posted the following:

    Because there have been so many arguments which allege the impossibility of eight people caring for so many animals, I delved into actual manpower studies on the time required to care for a given number of animals under various conditions. It turns out that simple labor-saving techniques could have enabled eight people to care for 16,000 rat-sized animals assuming the availability of only rustic tools, along with a 10-hour day, 6-day week, with time to spare. (bold added)

    Yet when I just checked I read the following:

    Because there have been so many arguments which allege the impossibility of eight people caring for so many animals, I delved into actual manpower studies on the time required to care for a given number of animals under various conditions. It turns out that simple labor-saving techniques could have enabled eight people to care for 16,000 animals assuming the availability of only rustic tools, along with a 10-hour day, 6-day week, with time to spare.

    ICR Impact #273

    Note there isn’t anything about 16,000 rat-sized animals.

    But thanks fer playin’…

  28. Joseph

    From your link:

    Since most of the animals were small, the median animal on the Ark was about the size of a rat.

  29. Indeed, which is why I wrote “Original.” The text has been changed, unless this guy is lying:

    http://members.cox.net/ardipit.....ie027.html

  30. HodorH

    That was fast. I was just about to post the same link. A google found it quickly.

  31. DaveScot:
    From your link:

    Since most of the animals were small, the median animal on the Ark was about the size of a rat.

    HodorH already posted that, but he also cut off part of the paragraph.

    It should be noted that Woodmorrape did NOT use this “median” to calculate the space requirements of the Ark. Anyone who reads eiether the Impact article or the book knows this. He also states that “only 15% of the animals were sheep-size or larger”.

    In the book he does NOT state anything about taking care of 16,000 “rat-sized” animals. Seeing that the book came out before the article that should be considered first.

    (I would never take an anti-ID or anti-Creation word for anything. Especially given their penchant for deception.)

  32. It should be noted that Woodmorrape did NOT use this “median” to calculate the space requirements of the Ark.

    Well, I don’t have the book, and I’m not buying it, but Jonathan Sarfati does have a summary of the relevant bits. http://www.answersingenesis.or.....nimals.asp

    If the animals were kept in cages with an average size of 50x50x30 centimetres (20x20x12 inches), that is 75,000 cm3 (cubic centimetres) or 4800 cubic inches, the 16,000 animals would only occupy 1200 m3 (42,000 cubic feet) or 14.4 stock cars.

    That’s a rat-sized cage. Is AiG misrepresenting Woodmorappe?

  33. It should be noted that Woodmorrape did NOT use this “median” to calculate the space requirements of the Ark.

    HodorH:
    Well, I don’t have the book, and I’m not buying it, but Jonathan Sarfati does have a summary of the relevant bits.

    Is something wrong with what Woodmorappe states in Impact #273?

    To calculate the housing space needed by the animals, I employed laboratory-animal housing standards for reference animals of comparable mass. Also, by using the body-weight categories, and actual measurements of animal-food intake, I was able to determine how much food and water the animals would need for their 371-day Ark stay. Special emphasis was placed on the large mammalian herbivores and their ostensible requirement for vast quantities of bulky hay. It turns out that the Ark was more than ample to accommodate the animals along with their water and provender, with considerable room to spare.

    Also Sarfati says “If”, and uses “average”. Wouldn’t it have been the “median size”…

    I provided a link to Woodmorappe’s article. Why would you venture to AiG to find anything else?

    It fully appears to me that Woodmorappe calculated the median just for something to do given the data he gathered and the pattern he saw.

    and again thanks fer playin’…

  34. It fully appears to me that Woodmorappe calculated the median just for something to do given the data he gathered and the pattern he saw.

    Yes, just for kicks and giggles I’m sure. I know when I write papers, I make sure to put in lots of irrelevant data.

    I provided a link to Woodmorappe’s article. Why would you venture to AiG to find anything else?

    Gosh, perhaps because I already read Woodmorappe’s article, and you suggested that we “consider what the book says first?” See that dot? There’s a one next to it. See that other dot? It has an adjacent two. Now think back to your early education.

    Also Sarfati says “If”, and uses “average”. Wouldn’t it have been the “median size”…

    So, Sarfati is saying the mean cage size is rat-sized (and that rat-sized cage is my interpretation – you sure couldn’t fit a sheep in a cage that size, which is the mean size estimated by other creationists). It appears that the mean cage size was determined by figuring out the median animal size. If he had used the median animal size to figure out the median cage size, that would be mathematically sound, but useless.

    and again thanks fer playin’…

    You’re welcome. I can only hope that you are.

  35. Oy Vey! I include one throw-away line about YEC’s and their front-loading ideas, and a discussion of the size of the critters in the ark takes over the thread. Enough already.

  36. Si, capitan! No more flavorless oatmeal for me!

  37. HodorH: Sorry, that is far too lenient. B’sun, stop his grog!

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