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On Whales Legs

Sperm Whale Engineering Manual
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It is common nowadays to hear pleas for the teaching of Creationist "science" together with evolution in high schools and universities.  If implemented this prospect would make a mockery of our educational system and would be tantamount to teaching the Flat Earth theory alongside conventional geography.  Although there are countless reasons why I believe this to be the case, I would offer the following argument from the fossil record of whales as providing compelling support for the evolutionary position.

It has been known since Darwin's time that whales occasionally show evidence of vestigial limbs and pelvic structures.  This is most obvious in whale embryos, but adult whales have actually been found with protruding limb rudiments.  (See the discussion in P. Gingerich et al, "Hind Limbs of Eocene Basilosaurus: Evidence of Feet in Whales," Science 249, July 13, 1990, p. 154).  Why would an animal be born with traces of legs when it currently has no use for them?  That the vestigial stumps have no functional purpose in modern whales is obvious. How, then, are we to explain the case of the whale's vestigial structures in a logical and scientific manner?

The evolutionist position is at once simple and perfectly logical: modern whales have vestigial legs and pelvic girdles precisely because they evolved from land animals with legs (most likely artiodactyls, an ungulate mammal of which hippos are perhaps the best modern example).

It would thus stand to reason that the earliest whales had fully functional legs and that only later did their legs begin to diminish in utility to the point at which they appear in modern whales as vestigial stubs concealed beneath the blubber.  It is to be expected, moreover, that various intermediate forms will be found between early whales with fully functional hind limbs and modern whales with vestigial limbs only. 

What, then, does the fossil record reveal?  Early whales, as exemplified by Ambulocetus natans, show well-formed fully functional hind legs.  Two other whales--Indocetus ramani and Rodhocetus kasrani--appear later in the fossil record and show diminished although still perfectly functional hind limbs.  Basilosaurus isis, finally, had very tiny hind limbs the utility of which is unknown.  (See the bibliography appended at the end of this note for the relevant scientific literature on these respective animals).  In the case of Rodhocetus, at least, where the pelvis is well-preserved, there can be no doubt but that the legs were attached to the pelvic girdle and that they were functional.  As P. Gingerich et al note in their analysis of the whale in question, "The pelvis of Rodhocetus articulates with the vertebral column by normal mammalian sacral synarthroses, meaning that Rhodocetus could support its body weight on land." ("New whale from the Eocene of Pakistan and the origin of cetacean swimming," Nature 368, 1994, p. 847).

The standard Creationist response when confronted with this compelling evidence from paleontology is to simply ignore it.  Indeed I know of no credible, substantive attempt to deal with the issue of the whale's vestigial structures to be found anywhere in the Creationist literature.  One possible explanation for the whale's vestigial legs--one I've heard more than once in debates with Creationists--is to view them as the product of random mutations.  Yet there is every reason to conclude that this is a most unlikely possibility.

If the Creationists are right, it stands to reason that other vertebrates would be subject to similar random mutations.  Sharks, for example, might develop vestigial limbs and hip girdles just like whales.  This hypothetical position stands in direct contrast to the evolutionist position, which holds that *only those vertebrates which evolved from land animals can be expected to show traces of hind limbs*.  Thus, it is well-known that various species of snakes show unequivocal evidence of vestigial hind limbs (boas, for example).  As reptiles, snakes evolved from amphibians which originally had legs.  Sharks, on the other hand, do not display vestigial hind limbs for the simple reason that they are fish and thus owe their origin to the prochordates, none of which ever possessed legs.  Much as the presence of vestigial limbs in whales and snakes  constitutes conclusive support for the evolutionist position, so too does the lack of vestigial hind limbs in sharks serve to undermine the Creationist position.

In an essay entitled "Senseless Signs of History," Stephen Gould makes a point of direct relevance to our ongoing discussion about the hip-sockets of whales.  Gould's subject was how Darwin went about distinguishing his hypothesis of evolution from that espoused by Biblical creationists:

"How do we know that a modern result [the whale] is the product of alteration through history and not an immutable part of a changeless universe?  This is the problem that Darwin faced, for his creationist opponents did view each species as unaltered from its initial formation.  How did Darwin prove that modern species are the products of history?  We might suppose that he looked toward the most complex and perfected adaptations of organisms to their environments: the butterfly passing for a dead leaf...Paradoxically, he did just the opposite.  He searched for oddities and imperfections.  The gull may be a marvel of design; if one believes in evolution beforehand, then the engineering of its wing reflects the shaping power of natural selection.  But you cannot demonstrate evolution with perfection because perfection need not have a history.  After all, perfection of organic design had long been the favorite argument of creationists, who saw in the consummate engineering the direct hand of a divine architect...But, Darwin reasoned, if organisms have a history, then ancestral stages should leave *remnants* behind.  Remnants of the past that don't make sense in present terms--the useless, the odd, the peculiar, the incongruous--are the signs of history.   They supply proof that the world was not made in its present form...Why should the fetus of a whale make teeth in its mother's womb only to reabsorb them later and live a life sifting krill on a whalebone filter, unless its ancestors had functional teeth and these teeth survive as a remnant during a stage when they do no harm?" (The Panda's Thumb, pp. 28-29)

Why indeed? 

Bibliography:

 

J. Thewissen, S. Hussain, M. Arif, "Fossil Evidence for the Origin of Aquatic Locomotion in Archaeocete Whales," Science 263, Jan. 14, 1994, pp. 210-212.

P. Gingerich et al, "New whale from the Eocene of Pakistan and the origin of cetacean swimming," Nature 368, April 28, 1994, pp. 844-847.

P. Gingerich et al, "Hind Limbs of Eocene Basilosaurus: Evidence of Feet in Whales," Science 249, July 13, 1990, pp. 154-157.