A question of diversity

When I taking biology in high school science seemed so simple. Lyell was a uniformitarian hero, Cuvier was a brillant anatomist (but sadly a narrow-minded catastrophist), Charles Darwin was the hero of all biology, and Lamarck was the official whipping boy of evolutionary science, the deconstruction of his ideas receiving more time than Darwin's theory of evolution by natural selection! In the years following my graduation in 2001 I didn't think too much about the issue, the work of naturalists who lived centuries ago hardly seeming relevant to modern science. Fortunately, I realized how incredibly ignorant this was and have been trying to learn as much as I can about naturalists of prior centuries (reading their actual works whenever possible), and the picture of the evolution of the science of natural history is far more complex than I had previously imagined.

Presently I'm still working on Gould's The Structure of Evolutionary Theory, a monstrous tome that is heavy on scientific history, but this week I have taken a bit of a break to read a few other books as a refresher. I started out on Sunday with Adrienne Mayor's Fossil Legends of the First Americans and read Stanley Hedeen's Big Bone Lick shortly thereafter (I will have a review of Hedeen's book shortly), and now I've moved on to Martin Rudwick's Georges Cuvier, Fossil Bones, and Geological Catastrophes. Indeed, Cuvier's study of the American "incognitum" from Big Bone Lick (now known as the American mastodon, Mammut americanum) is a connecting thread between all these works, and if I'm correct those fossils may have had a very important effect on why Cuvier never came to accept evolution as a fact.

As I was reading Rudwick's translation of some of Cuvier's papers, the self-assured (if not arrogant) manner of Cuvier definitely came across; he was a young anatomist trying to make the field of comparative anatomy more rigorous, and he didn't suffer the flimsy speculations of his predecessors (including Buffon). Clearly he was a man out to prove himself, and some of his most important ideas (indeed, the concepts we know him for today) involved catastrophes and extinction. As Gould noted in Time's Arrow, Time's Cycle, Cuvier's notion of catastrophism was not oppossed to Lyell's later formulation of uniformitarianism, and there is a passage in Rudwick's book that makes this especially clear. In an excerpt of "Extract from a work on the species of quadrupeds of which the bones have been found in the interior of the earth; addressed to savants and amateurs of the sciences, by G. Cuvier, member of the Institute, professor at the College de France and at the Pantheon central school, etc.," Cuvier is explicit about the need to study geology directly and not merely speculate about it;

They [earlier savants that developed systems of the earth] first guessed at nature rather than studying it; the others, while thinking they are only verifying the systems they admire, study it truly; and it is thus that the sciences - like peoples - pass from poetry to history.

The history of the earth has thus taken a new direction in the past twenty years. The Saussures, Pallases, and Dolomieus were less eager to attract the admiration of their contemporaries by brilliant but fragile edifices, than to set in place some solid foundations on which posterity could one day construct a lasting monument. They rejected all "system"; they recognized that the first step to make in divining the past was to establish the present firmly. [emphasis mine]

Cuvier, of course, was among those that studied the history of the earth truly, and the relationship between the American mastodon, Siberian mammoth, and living African & Indian elephants would play a key role in his insistence of extinction as a real phenomena and (perhaps) his rejection of Lamarck's hypothesis of evolution. The rough teeth of the mastodon were known by 1705 at the latest, but the most celebrated remains (from the most famed site) did not come out of the ground until 1739 when Native Americans brought mastodon remains back to camp while hunting food for the troops of Baron Charles de Lougueuil in Ohio (see Mayor's book for the generally overlooked contribution of the Native Americans in this oft-told tale).

The teeth and tusks ultimately made their way back to France, but the rough teeth of the mastodon were so different from those of an elephant (to which they were somewhat similar in overall form) that Louis-Jean-Marie Daubenton proposed that the tusks were those of an elephant and the teeth were those of a hippopotamus. This would be a continuing trend, the teeth of the mastodon being so different from those of elephants that they were thought to either be from a different kind of animal altogether or from a carnivorous form of elephant, the legends of the Native Americans supporting the latter view. How the fossils of animals considered to be exclusively tropical also puzzled Daubenton and Buffon, and the Noachian Deluge was invoked to explain the transport of the bones so far north.

Confusion about the teeth, tusks, and bones coming out of Big Bone Lick (and elsewhere) continued for some time, but ultimately Cuvier set the matter to rest in 1796 in "Memoir on the Species of Elephants, Both Living and Fossil." (collected with several other papers and recently reprinted). Not only did Cuvier demonstrate that the American mastodon (or the "Ohio Animal") was distinct from the mammoths being found in Siberia, but that both were distinct from modern African & Indian elephants, another division that Cuvier effectively proved. Of perhaps greater importance, however, Cuvier was certain that these distinct species no longer existed. From "Memoir on the Species of Elephants, Both Living and Fossil" translated in Rudwick's book;

What has become of these two enormous animals [the Siberian mammoth and the American mastodon] of which one no longer finds any [living] traces, and so many others of which the remains are found everywhere on earth and of which perhaps none still exist? The fossil rhinoceros of Siberia are very different from all known rhinoceros. It is the same with the alleged fossil bears of Ansbach; the fossil crocodile of Maastricht; the species of deer from the same locality; the twelve-foot-long animal, with no incisor teeth and with clawed digits, of which the skeleton has just been found in Paraguay: none has any living analogue. Why, lastly, does one find no petrified human bone?

All these facts, consistent among themselves, and not opposed by any report, seem to me to prove the existence of a world previous to ours, destroyed by some kind of catastrophe.

Cuvier, acting modest in the rest of the conclusion, states that he has only served as an anatomist to open up a new "highway" for a genius to pursue the question further, but the power of the argument is clear. The mastodon, the mammoth, the "crocodile" (which would later be named Mosasaurus by Cuvier), and the animal with "clawed digits" (which would be named Megatherium, also by Cuvier) no longer existed anywhere else in the world, and past diversity could not be accounted for under any of the various "systems" in fashion during Cuvier's time. As Rudwick states in a footnote on pg. 48 of his book, the transportation of bones/organisms, the transmutation of organisms, and the extinction of organisms were seen as three alternative explanations for why the fossil bones of so many bizarre animals were coming to light. In the case of transportation the Biblical flood was usually invoked to explain why fossils should should up out of place, and it was suggested that unusual forms were simply hiding in unexplored regions as the sustaining "great chain of being" could not be broken. Cuvier rightly rejected this, but transmutation was a bit trickier.

Evolution by natural selection, as proposed by Darwin, would not breach scientific circles until more than 50 years after Cuvier put out his call for international collaboration on fossil finds (see "Extract from a work..." quoted above), but Cuvier was active in scientific circles during the rise of Lamarckism. Under Lamarckism, evolution was not a branching process as envisioned by Darwin, but almost like a conveyor belt of species increasing in complexity in a straight line, almost manifesting the "great chain of being" through time. As creatures evolved away from the most basic, ancestral state, this left an opening for other basic creatures to fill and start moving up. Of further importance was that creatures did not become extinct in this system and so fossil remains would have to be representative of living species. I am not expert on the history of science and I do not know in detail what Cuvier thought of his Lamarck's work on evolution (at least not yet), but this surely would have been a sticking point.

Under Lamarck's program the fossil elephants Cuvier took so much time to describe would ultimately only be prior forms of the living African and Asian elephants, undercutting Cuvier's important ideas of extinction and catastrophes in the distant past. Indeed, it seems that Lamarck's concept of evolution could only reconcile past diversity by claiming that those creatures only represented a past form and that the modern descendants look different, but I would bet that Cuvier might have wondered just what animal the "Monster of Maastricht" evolved into, or why Indian elephants lost all their hair and retired to the tropics.

I cannot be at all sure of my hypothesis about why Cuvier rejected evolution, but I have to wonder how history might have gone differently if either Lamarck's hypothesis was better able to reconcile past & present diversity or if Cuvier considered the evolution of diversity instead of rejecting Lamarck's system. As I said at the beginning of this wandering post, Cuvier seemed like he had a lot to prove, so perhaps part of his rejection of evolution involved the promotion of his own ideas about geologic history as he certainly saw himself as a man apart from other savants. If I'm in any way right, then, Cuvier's rejection of evolution further underlines why Darwin's formulation of evolution by natural selection was so important; Darwin's theory not only recognized natural selection as a viable mechanism of evolutionary change, but his concept of evolution as a branching process leading to diversification successfully reconciled the variety of extinct and extant taxa. As I continue to read Cuvier perhaps I'll find out that I've somehow erred or that this idea has already been duly considered by historians of science, but the idea struck me with enough force that I simply cold not let it alone.

Further reading;

Academy of Natural Sciences - Discovering the Mastodon

American Monster by Paul Semonin