Friday, February 06, 2015

John F. Kennedy, Carnival cruises, blood plasma, sea water, and evolution

Here's a video of a commercial by Carnival Cruises. Apparently it aired during some recent football game in the USA. (They play football in January?)

The voice is that of US President John F. Kennedy. He says ...
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’s 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.
Here are the facts as I explain them in the latest edition of my textbook (p. 33).

There was a time when people believed that the ionic composition of blood plasma resembled that of seawater. This was supposed to be evidence that primitive organisms lived in the ocean and land animals evolved a system of retaining the ocean-like composition of salts.

Careful studies of salt concentrations in the early 20th century revealed that the concentration of salts in the ocean were much higher than in blood plasma. Some biochemists tried to explain this discrepancy by postulating that the composition of blood plasma didn’t resemble the seawater of today but it did resemble the composition of ancient seawater from several hundred million years ago when multicellular animals arose.

We now know that the saltiness of the ocean hasn’t changed very much from the time it first formed over three billion years ago. There is no direct connection between the saltiness of blood plasma and seawater. Not only are the overall concentrations of the major ions (Na+, K+, and Cl-) very different but the relative concentrations of various other ionic species are even more different.

The ionic composition of blood plasma is closely mimicked by Ringer’s solution, which also contains lactate as a carbon source. Ringer’s solution can be used as a temporary substitute for blood plasma when a patient has suffered blood loss or dehydration.
Here's a copy of something I posted on on Oct. 5, 1998.
It turns out that one of the most important researchers who investigated this problem was A.B. Macallum who was chair of my department from 1907-1917. [See Archibald Byron Macallum (1858 - 1934)] Macallum wrote a major review in 1926 (1) in which he debunked the idea that the ionic composition of blood plasma was nearly the same as that of sea water. Here's what he said seventy years ago,
"Quinton, in 1897 (2), 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, chuphur, silicon, carbon, phosphorus, fluorin, 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."
p. 320-321
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 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.

1. Macallum, A.B. (1926) The Paleochemistry of the Body Fluids and
Tissues. Physiol. Rev. 6, 316-357.

2. Quinton, R. (1898) Hypothese de l'eau de mer, milieu vital des
organisimes eleves. Compt. rend. de la Soc. de Biol. 935
I added more information on May 30, 2005.
The concentration of salts in seawater is more than three times higher than the concentration in most organisms. For example, the ionic concentration of seawater is 600 millequivalents and that of human blood plasma is only 150 milliequivalents. The same difference holds true for most species, including many single-cell organisms. Many bacteria can live quite happily in the sea or in fresh water because they are not dependent on the ionic composition of the surrounding medium. Many organisms are not isotonic with their surrounding if by "isotonic" one means within a few percent.

Perhaps modern salt concentration in human plasma reflects that of the ancient ocean? This idea has been around for a long time. The original chair (1907) of my department was A.B. Macallum and he was a leading proponent of this concept. The most widely cited paper was a review published near the end of three decades of work on this subject.

Macallum, A.B. (1926) The Paleochemistry of the Body Fluids and Tissues.
Physiol. Rev. 6: 316-357.

(Finding this paper was quite an adventure - I've told the story before on

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.

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.
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.

That's still a problem today. Here's the former President of the American Society of Hematology repeating the myth in 2008 [The Wonders of Blood].
Our blood is the foundation of our very existence as multicellular animals, said Andrew Schafer, a professor at Weill Cornell Medical College and the outgoing president of the American Society of Hematology. Blood is the one tissue that comes into contact with every other tissue of the body, and it is through blood that our disparate parts communicate, through blood that our organs cooperate. Without a circulatory system, there would be no internal civilization, no means of ensuring orderly devotion to the common cause that is us.

“It’s an enormous communications network,” Dr. Schafer said — the original cellphone system, if you will, 100 trillion users strong.

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.

Note: PZ Myers didn't like the commercial either ["]. One of his reasons was that the facts are wrong.


  1. .. .Macallum wrote a major review in 1926 (1) in which he debunked the idea that the ionic composition of sea water was nearly the same as that of sea water.
    Sea water is the same as sea water? That's a no-briner.

  2. It turns out that one of the most important researchers who investigated this problem was A.B. Macallum who was chair of my department from 1907-1917

    … and was also Maud Menten's first co-author (in 1906), and the one who sparked her interest in measuring ion concentrations, thus (probably) stimulating her desire to work with Michaelis in one of the leading laboratories in the world for studying hydrogen ions. I suspect she was more interested in learning how to deal with hydrogen ion concentrations than she was in the kinetic analysis that made her famous.Certainly, she continued her interest in ions after she returned from Germany, but as far as I know she did nothing further in enzyme kinetics.

  3. Of course the real story is more complicated.
    Nearly all marine invertebrates are osmoconformers and damn near ionoconformers as well: their extracellular fluids, including blood if they have it, are very very close to the osmotic and ionin composition of seawater.
    The same is true of one kind of vertebrate: the hagfishes. If Kennedy was a hagfish he'd have been correct.
    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.
    These issues are well known to evolutionary biochemists like Hochachka & Somero ( and are discussed in every textbook of comparative physiology.
    A couple more refs: