Professor Larry Moran has written a post in which he skilfully debunks the hoary old myth that the ionic composition of blood plasma matches that of seawater, which is supposed to “prove” that our ancestors came from the sea. In a post titled, John F. Kennedy, Carnival cruises, blood plasma, sea water, and evolution (February 6. 2015), Professor Moran traces the history of this myth and the curious story of the man who first debunked it, only to propagate another scientific myth of his own making.
For the benefit of readers, I should point out that the myth that blood plasma has the same concentration of minerals as sea water has also been debunked by creation scientist Dr. John D. Morris in a 2004 article titled, Does the Similarity of Human Blood to Sea Water Prove Life Originated in the Ocean? (Acts & Facts 33 (2)), and more recently by Dr. Jerry Bergman in an article titled, Is the Sodium Chloride Level in the Oceans Evidence for Abiogenesis?, (Answers in Genesis, September 1, 2010).
People who swallowed the myth: a President, a Vice-President and many eminent scientists
The myth that the concentration of salts in our blood plasma matches that of sea water is a surprisingly resilient one, which has been swallowed, hook, line and sinker, by people at the highest levels of society – including Presidents.
At a dinner for the America’s Cup yacht crews in Newport, USA, given by the Australian Ambassador, Sir Howard Beale, on September 14, 1962, then US President John F. Kennedy remarked:
I really don’t know why it is that all of us are so committed to the sea, except I think it is because in addition to the fact that the sea changes and the light changes, and ships change, it is because we all came from the sea. And it is an interesting biological fact that all of us have, in our veins the exact same percentage of salt in our blood that exists in the ocean, and, therefore, we have salt in our blood, in our sweat, in our tears. We are tied to the ocean. And when we go back to the sea, whether it is to sail or to watch it we are going back from whence we came.
(Public Papers of the Presidents: p. 684, 1962.)
Professor Moran quotes this passage in his post (though he does not provide a reference, as I did). But President Kennedy wasn’t the only politician to remark on the resemblance between blood and sea water. Former Vice-President and 2000 Presidential candidate Al Gore, who took some environmental science classes before graduating from Harvard with an A.B. cum laude, in June 1969, wrote a best-selling book titled, Earth in the Balance, in which he asserted:
But above all we are oxygen (61 percent) and hydrogen (10 percent), fused together in the unique molecular combination known as water, which makes up 71 percent of the human body.
So when environmentalists assert that we are, after all, part of the earth, it is no mere rhetorical flourish. Our blood even contains roughly the same percentage of salt as the ocean, where the first life forms evolved. They eventually brought onto the land a self-contained store of the sea water to which we are still connected chemically and biologically. Little wonder, then, that water carries such great spiritual significance in most religions, from the water of Christian baptism to Hinduism’s sacred water of life.
(Gore, A., Earth in the Balance: Ecology and the Human Spirit, Houghton Mifflin Company, New York, NY, USA, pp. 99–100, 1992.)
The percentage of the human body which is made up of water actually varies from 50 to 78%, being about 75-78% in infants, 60% in men and 55% in women, so Vice-President Al Gore’s figure of 71% is in the right ball park. But his assertion that our blood “contains roughly the same percentage of salt as the ocean” is flat-out false. As Professor Moran demonstrates in his post, it was shown to be false as far back as 1926.
Why, then, has the myth been so widely accepted by the public at large? As Dr. Jerry Bergman documents in his article, Is the Sodium Chloride Level in the Oceans Evidence for Abiogenesis? (Answers in Genesis, September 1, 2010), the myth was widely propagated in science textbooks during the twentieth century – especially between 1940 and 1970. But even now, there are still respectable scientists who perpetuate this myth.
In his post, Professor Moran quotes an excerpt from a New York Times article titled The Wonders of Blood (October 20, 2008), by science correspondent Natalie Anger, in which no less a person than Andrew Schafer, a professor at Weill Cornell Medical College and the outgoing president of the American Society of Hematology, endorses the myth that the ionic composition of blood plasma matches that of sea water:
Blood can also be thought of as a private ocean, a recapitulation of what life was like for all the years we spent drifting as microscopic, single-celled organisms, “taking up nutrients from sea water and then eliminating waste products back into sea water,” Dr. Schafer said. Not only is blood mostly water, but the watery portion of blood, the plasma, has a concentration of salt and other ions that is remarkably similar to sea water.
The myth that human blood plasma has about the same salt content as sea water continues to thrive on the Internet as well. Although it was debunked on the Straight Dope Website some 15 years ago, the myth continues to be widely circulated online – see here, here, here, here, here, here and here for examples.
In my post today, what I’d like to do is show my readers how this pernicious myth continues to infect evolutionary thinking about the origin of kidneys in vertebrates. But before I do that, I’d like to take a brief look at how the myth got started, and how Archibald Macallum, the hero of Professor Moran’s post, did not really debunk this myth, but rather refined it, thereby giving it an extra lease of life and duping the public with a bad argument for evolution.
How the myth got started
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The first scientist to propose that the composition of the salts in our blood plasma matches that of sea water was French physiologist Rene Quinton (pictured above, courtesy of Wikipedia), who made this assertion in an article titled, “Hypothese de l’eau de mer, milieu vital des organismes eleves” (Comptes rendus des séances de la Société de biologie et de ses filiales, 30 October 1897 [not 1898, as Moran incorrectly states in his post], pp. 935-936). In 1904, Quinton wrote a book in which he expanded on his theme. Summarizing his findings on page 320, Quinton remarked on the striking similarity in composition (“analogie frappante de composition”) between the “vital milieu” of the “highest mammals” and the mineral composition of sea water.
Archibald Macallum: Debunker of one myth, creator of another
In his recent post, Professor Moran takes pains to point out that this “old urban legend” (as he described it back in 2001) was originally debunked by the Canadian biochemist Archibald Macallum, FRS (1858-1934), who was chair of physiology at the University of Toronto from 1901-1917. In a 1926 review titled, The Paleochemistry of the Body Fluids and Tissues, Macallum criticized Quinton for his sloppy methodology:
Quinton, in 1897, advanced the view that in the great majority of multicellular animals organisms the internal medium, the circulatory fluid, or hemolymph, is, as regards its organic composition, but sea water…. Analysis of the salts of the blood plasma, Quinton holds, indicates that they are the same as those which obtain in sea water and the elements of both appear in the same order of importance; Chlorine, sodium, potassium, calcium, magnesium, sulphur, silicon, carbon, phosphorus, fluorine, iron, nitrogen, etc. …
This indicates how uncritical he is in the examination of his data in his aim to demonstrate that the internal medium is but sea water. The elements do not appear in the same order of importance as stated. In sea water they rank thus: chlorine, sodium, magnesium, potassium, sulphur, calcium, etc., whereas in the blood plasma they rank: chlorine, sodium, potassium, calcium, sulphur, magnesium etc. In sea water the sodium is to the magnesium in amount as 100:12, whereas in the blood plasma of the higher vertebrates the ratio is as 100:0.7, which reveals a wide discrepancy. As regards the sulphur, which occurs almost wholly in sea water as sulphates, it is in amount in proportion to the sodium as 8.4:100, whereas in mammalian blood plasma if all the sulphur therein is reckoned as present in the form of sulphate, the proportion is 1.4:100.
(Macallum, A.B. (1926) The Paleochemistry of the Body Fluids and Tissues. Physiology Review 6, 316-357. The quote is from pp. 320-321.)
In an article which was originally posted on Talk Origins on Oct. 5, 1998 but which is unfortunately no longer online, Professor Moran discusses the strengths and weaknesses of Macallum’s reasoning:
Macallum reviews his own extensive data on ionic composition and points out that not only the proportions but also the concentrations do not agree. The salt concentration of plasma is “less than one-fourth that of sea water”.
Macallum was a confirmed evolutionist and he went on to argue that the salt concentration of mammalian plasma may reflect that of the ancient ocean where our ancestors lived. He was under the impression that the salinity and composition of the oceans has changed over the past several hundred million years. (We now know that this is not correct.) Furthermore, the ionic composition of cells is quite different from that of the plasma and Macallum suggests that this is a reflection of an even more ancient origin of cells in a Archaen (sic) ocean.
The point is that our blood is NOT like sea water. The sea is much more salty and the relative concentrations of the various ions is different.
How Archibald Macallum fashioned Quinton’s old myth into a new one
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While Professor Moran correctly notes that Macallum’s hypothesis that the salt concentration of mammalian blood plasma matches the concentrations of salts in the primordial oceans was wrong, what he fails to mention was that Macallum’s contemporaries did not perceive him as debunking Quinton’s original “sea water” myth so much as refining it. As his official obituary in the Obituary Notices of Fellows of the Royal Society (1934, vol. 1, pp. 287-291) put it:
The other field in which he [Maccallum – VJT] worked for long was the quantitative determination of the positive inorganic ions in the body fluids of vertebrate and invertebrate animals. He established the fact that the proportion in which Na, K, Ca, Mg occur in these fluids is extraordinarily like those in which they occur in sea water. In marine invertebrates with a vascular system communicating with the exterior the fluid that bathes the cells is sea water; in those with a closed system the fluid bathing the cells still contains these elements not only in the same proportions but in the same concentrations as the sea, and varies with that concentration where the sea is diluted with fresh water. This was doubtless the case, too, with the closely related forms their ancestors took when vertebrates were being evolved from them, only at that time the concentration of salts in the sea, which has been growing throughout history, was much less. In vertebrates, however, the power of preserving the osmotic pressure of the fluid bathing their cells, the milieu internale, at a uniform constant level is one of the most important distinguishing marks and must have been acquired from the first; that is to say, at that time, in the Silurian period or earlier, when they were being evolved and when the concentration of the salts in the sea was, he argues, that which is still found in their blood, less than a third of what it is in the sea today…
Among the higher vertebrates such minor differences in the ratios as he found he was prepared to set down to changes in those ratios in the sea which he gave reason for thinking must have occurred. (pp. 289-290)
“Must have occurred.” Notice the circular logic there?
What’s more, Macallum (pictured above, courtesy of Wikipedia) had a habit of explaining away awkward facts, as Professor Moran himself acknowledged in an update to his 1998 Talk Origins post, dated May 30, 2005:
Macallum published estimates of the salt concentration of the Cambrian sea and these estimates agree closely with the salt concentrations in modern human plasma. Unfortunately the salt concentrations in sharks and lobsters are twice as high as in humans so this meant that sharks and lobsters originally had salt concentrations that were higher that seawater. No problem. The salt in sharks and lobsters has increased over time as the ocean got more salty but the human values reflect the time when their ancestors emerged from the sea.
But as Moran points out, Macallum’s explanation fell foul of the facts:
It’s a nice idea but it was spoiled by a nasty little fact. The salt concentration of the oceans has not changed very much since they reached equilibrium about three billion years ago. Gould has a nice little essay about this in “On Rereading Edmund Halley” (EIGHT LITTLE PIGGIES p.168). In addition to discovering comets, Halley proposed a method for calculating the maximum age of the Earth based on the increase of salt in the ocean.
He was wrong for the same reason that Macallum was wrong.
Summing up. Professor Moran comments:
It’s interesting that the myth of blood plasma resembling sea water persisted for over a century in spite of the fact that leading biochemists knew the truth 75 years earlier. Part of the problem was textbook writers who perpetuated the idea because it seemed so sensible in light of evolution. (In fact, it’s not sensible at all if you really understand evolution.) Those textbook writers didn’t bother to check the scientific literature. Neither did the typical lecturer in a biochemistry course.
How the myth continues to survive among origin-of-life researchers
Judging from Professor Moran’s observation that the notion that the mineral composition of blood plasma should match that of sea water is “not sensible at all if you really understand evolution,” you might be forgiven for thinking that scientists had completely abandoned the idea. Not so. In an article in Scientific American titled, Did life evolve in a ‘warm little pond’? (February 16, 2012), Lucas Brouwers reports on a new hypothesis that life arose in volcanic pools, which cites Archibald Macallum’s work in support of this contention:
The researchers, led by Armen Mulkidjanian, presume that the chemistry of modern cells mirror the original environment in which life first evolved. Since oceans and cells are chemically dissimilar, they think it is unlikely life evolved there. The chemical nature of volcanic pools, or ‘warm little ponds’, resembles the cell’s composition of its cytoplasm much more closely.
The researchers invented the term ‘chemistry conservation principle’ for their idea that organisms retain their chemical traits throughout time. They reason that the membranes of the first cells must have been simple and leaky. Metal ions could have flowed in and out unhindered, leading to a equilibrium between environment and protocell. As the cells adapted to the ion levels in their surroundings, they came to depend on them. Circumstance became necessity. Cells evolved ion pumps and ion-tight membranes to maintain the ion balance that was initially forced upon them – hence the assumption that cells themselves are reflections of their ancestral environment.
This is not a new approach. The Canadian biochemist Archibald Macallum applied it as early as 1926, when he noted that ion levels were similar between blood and sea water and concluded that animals must have evolved in the sea. “Maccallum was also the first to measure the concentrations of ions within cells”, says Mulkidjanian. “He discovered that all modern cells contain more potassium than sodium.”
This century old observation is one of the cornerstones of Mulkidjanian’s argument: potassium outnumbers sodium in living cells, yet in oceans and lakes, sodium dominates. Other ions, like zinc, magnesium and phosphate are also present in much higher concentrations in modern cells than they are in oceans of past and present.
However, as Brouwers points out, not all origin-of-life scientists buy this ‘chemistry conservation principle’:
“The ‘principle of chemistry conservation’ is a postulate rather than a proven principle“, says Jim Cleaves from the Carnegie Institution of Washington. “It may be true on short time scales, but who can say what has happened since the origin of life?”
“Overall, I think it is questionable that organisms would have kept their original composition, given the variability observed in present cells. Is it not at least equally likely that they have modified their cytosolic composition once they had control over this process? Any modern environment which matches this composition would then be purely coincidental. In summary, I don’t get much from this paper that I would hang my hat on.”
Jack Szostak, professor at Harvard Medical School and 2009 winner of the Nobel Prize, has similar doubts about the chemical conservation principle, but he does not dismiss volcanic pools entirely.
So there we have it. Evolutionary scientists studying the origin of life can’t make up their minds as to whether the mineral composition of ions within cells should match that of the medium in which they first arose, or whether it shouldn’t. Confusion reigns.
How some evolutionists continue to stubbornly cling to the “plasma equals water” myth
Interestingly, even after Professor Moran, who is a highly respected biochemist, wrote his post on Sandwalk which totally demolished the “sea water matches blood plasma” myth, one evolutionist felt bound to defend a modified version of the myth. In a comment on Professor Moran’s post, Chas Peterson argued that the composition of ions in our blood plasma can indeed tell us something about our evolutionary origins. Our blood plasma, according to Peterson, shows that vertebrates evolved in estuaries.
Pretty much all other vertebrates, be they fish (freshwater or marine; though sharks are a little weird), amphibians, or amniotes (terrestrial, freshwater or marine) are osmoregulators, maintaining very similar ECF concentrations to the anthropocentric discussion in the OP, about 1/3 that of seawater but of very similar (though no, not precisely exactly the same) relative proportions of the major ions.
It costs significant amounts of energy for both freshwater and marine fishes to maintain their plasma at such different concentrations from their environment. That makes it an interesting evolutionary question.
Most recent discussions have concluded that the evidence best supports the hypothesis of an estuarine/osmoconforming origin of vertebrates. That is, our body fluids do, in fact, closely resemble the external environment of our ancestors, it’s just that that environment was not full-on seawater.
Unfortunately, the facts don’t match Mr. Peterson’s assertions. First, regarding the origin of vertebrates: if we confine our attention to actinopterygians, or ray-finned bony fish, scientists have concluded that their ancestors did indeed arise in estuaries. That’s the upshot of a 2012 paper by Greta Vega and John Wiens, titled, Why are there so few fish in the sea? (Proceedings of the Royal Society B, doi:10.1098/rspb.2012.0075). (Interested readers can find a discussion of this paper in Jerry Coyne’s post, Nearly all marine fish came from freshwater ancestors (Why Evolution Is True, February 16, 2012) and Alasdair Wilkins’ online article, Most fish evolved in freshwater (io9.com, 7 February 2012).) But the paper says nothing about lobe-finned fishes, or about cartilagenous fishes (sharks, rays, skates and ghost sharks). Indeed, the vast majority of sharks die in fresh water, as the online article, Biology of Sharks and Rays by Dr. R. Aidan Martin explains. Hence it is simply incorrect to say that vertebrates originated in estuaries. The most we can say is that the ancestors of most living vertebrates did. The first vertebrates, however, arose in the oceans.
Second, the mineral composition of estuarine water doesn’t match that of blood plasma, either. Dr. Jerry Bergman, who taught biology, genetics, chemistry, biochemistry, anthropology, geology, and microbiology at Northwest State College for over 25 years, convincingly demonstrates in his online article, Is the Sodium Chloride Level in the Oceans Evidence for Abiogenesis?, that the ionic composition of blood plasma doesn’t match that of sea water or fresh water. This disparity holds, regardless of whether we are considering the absolute concentrations of mineral ions or the relative proportions of those ions. And there’s more. Here’s the abstract of a recent paper by A. G. Becker et al. on teleosts [or bony fish] that was published in Neotropical Ichthyology, 9(4): 895-900, 2011, titled, Plasma ion levels of freshwater and marine/estuarine teleosts from Southern Brazil:
The purpose of this study was to investigate Na+, Cl-, K+, Ca2+, and Mg2+ levels in the plasma of freshwater and marine/estuarine teleosts collected at different salinities (0 to 34) from the estuarine and freshwater portions of the São Gonçalo channel in Southern Brazil. Any relationship between plasma ion levels and salinity and the capacity of ionic regulation of teleosts found at three or more different salinities (Genidens barbus and Micropogonias furnieri) was also investigated. Results showed no relationship between plasma ion levels and salinity when considering all species together, but the two species collected from three or more different salinities showed a significant positive relationship between plasma ion levels and salinity, indicating that G. barbus and M. furnieri have a high capacity to regulate plasma ion levels at both low and high salinities.
The myth returns, in a new guise, to the Talk Origins Website
But it gets worse. As you’ll recall, Professor Moran debunked the link between blood plasma and sea water on a Talk Origins post in 1998. But the myth continues to be propagated in a more recent Talk Origins post titled, Body Fluid Salinity (28 May 2005), written by a Professor Norman. (I have been informed that the professor is not Richard Norman, as I had previously believed, incorrectly. My sincere apologies to Richard Norman for the erroneous attribution. – VJT.) Here’s what he says in his article, when discussing the problem of how various kinds of animals manage to maintain the salinity of their body fluids in different environments:
Then there is the problem of terrestrial animals. For simplicity, I will only consider the terrestrial vertebrates — amphibians, reptiles, birds, and mammals (OK, I know there is no such thing as “reptile”, but no matter, the argument still holds). All these animals have body fluids roughly the same osmotic concentration as fresh-water fish, roughly 1/3 the concentration of sea water. In other words, this completely explains the original question — why humans have body fluids significantly less salty than sea water even though life first evolved in sea water. The answer is most definitely NOT that oceans were 1/3 as salty back then. It most definitely IS that the earliest vertebrates did evolve in salt water and then moved into fresh water. As an adaptation to avoid the osmotic effect of living the “type-two” way described above [where body fluids are significantly more concentrated than the environment – VJT], they dropped the salinity of their body fluids about as low as they could consistent with keeping their cells happy. From then on, all vertebrate evolution (including the lungfish and lobe-fin fish, the amphibians, the reptiles, the birds, and the mammals) all retained the ancestral body fluid concentration roughly 1/3 sea water.
Observe what Professor Norman is doing here. He dispenses with what I’ll call “Macallum’s myth,” only to substitute a new one of his own: that the concentration of various ions in terrestrial vertebrates’ blood plasma reflects their ancestors’ estuarine origins. As we saw above, this assertion is simply false.
Here are the concentrations of Na+, K+, Mg2+, Ca2+ and Cl- ions, measured in mM, in fresh water (average for N. America): 0.39, 0.04, 0.52, 0.21 and 0.23, respectively. Here are the concentrations in a terrestrial vertebrate (Homo): 142, 4, 5, 2 and 104. Here are the concentrations in average sea water: 470, 10, 10, 54 and 548. (Source: Harris, L. 1996. Concepts in zoology, 2nd ed. New York: Harper Collins, p. 276.) Not much of a correlation, is there?
Thus on the very Website – Talk Origins – where Professor Moran debunked the “blood plasma equals sea water” myth, a modified version of the myth has returned: blood plasma is now supposed to resemble estuarine water in its mineral content. Which Professor are readers supposed to trust: Moran or Norman?
Why, one wonders, can’t evolutionists agree on what their theory entails?