A question of diversity


The American mastodon (Mammut americanum), illustrated in one of Cuvier's memoirs.

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

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I am having difficulty reading your post because all that goes through my head is: holy shit, you graduated HIGH SCHOOL in 2001?!?!?!?!!!! I've been in grad school longer than you've been out of high school!

*bangs head on desk and weeps*

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!

To be fair, you can learn a lot about how evolution by natural selection works by deconstructing exactly why evolution by inheritance of acquired characteristics didn't work, and never could have. So some of that deconstruction should count as time devoted to Darwin's theory.

It's an interesting thought - where would Cuvier have gone, had he a model for speciation. I'm no historian of science, but it makes you wonder - there were two perfectly valid models that could have been applied. One is a hybrid origin for species. Mules were well known. As was the hybrid origin of the English and French nations - Anglo-Saxon + Celt + Norman (themselves a hybrid people) for the English, Romano-Gaul + Frank for the French. The other model comes from the bible - the Tower of Babel, where God created the nations by giving them mutually incomprehensible languages (as does another hybrid people, the Samaritans).

It's all so simple with hindsight. :)

Derek; Deconstructing erroneous ideas can be helpful, but at the same time instruction on why the verified ideas hold true is also important. In my particular class we spent a lot of time talking about doberman tails and giraffe necks, but Darwin only got a brief nod and the way evolution actually proceeds was not effectively addressed. The point of the intro was that much of what I learned tried to narrow down the "important" subjects so far that the course ended up making caricatures of many naturalists, giving me the impression (which I think is somewhat harmful) that if something is old it's wrong and we can only appreciate the work of past naturalists in a historical context.

Elisabeth; It's not quite the same, but in the past I had made friends with freshmen who graduated before I did (my sister, who started a year after me as an undergrad, is now finishing her master's degree!). At least you got to grad school; I'm still hitting the undergrad ceiling much like a fly bangs against a window.

Okay, I'm back. Sorry for the age-induced hysteria.

So, when Cuvier posits a "the existence of a world previous to ours," what, exactly, does he mean by that? Does he mean an entire world that was utterly different that was completely destroyed and everything started all over again and it is in this world that we reside? Or did he mean that the previous world was one containing us and those fossils but some catastrophe killed off the fossil creatures while we survived.

Also, I assume from what you've written that Cuvier never tried to come up with a theory of evolution which would take into account his fossils?

P.S. My younger brother was kind enough to point out at Christmas that given that I am not likely to graduate before my next birthday, he will obtain his doctorate at a younger age that I will obtain my doctorate. Cheeky bastard.

Elisabeth; Thanks for the questions. Sometimes I forget that not everyone is familiar with these naturalists so it's good to be reminded that sometimes I need to fill in some background information. Cuvier was famous for his idea of catastrophism, so the fossil animals he discovered were alive in a time before humans and were destroyed by a great catrastrophe. During his time (and like one of the quotes suggests) no human fossil remains were known then, so he had no reason to think that we had lived alongside the fossil animals that were wiped out. He didn't propose that the "world" as a planet was destroyed, but more that the world was different in the past and a catastrophe changed what once was.

Also, Cuvier did not come up with a hypothesis for evolution, although some of his contemporaries (most famously Geoffrey) more or less did. Geoffrey and Cuvier engaged in a great debate over a number of years about science, but it was more of a debate about approaches to science than it was about evolution itself. Cuvier organized his natural history by function (parts of a body of an animal fit it to a particular role and functions, and if you change one part everything falls to pieces), while Geoffrey was more open to evolution and represented the "formalist" side of the issue (he tried to group all animal groups together by finding an archetype that could explain diversity of life but unite them all at the same time). The Cuvier/Geoffrey debate is a bigger issue for another time, but the short answer is that Cuvier did not come up with a hypothesis for evolution, but his focus on function (adaptation) was influential on natural theologian William Paley and in turn on Darwin.

The relationships between the successive generations of naturalists is very complex, moreso than just "X accepted evolution, his opponent did not." What a tangled bank we weave...

Sorry to hear about your brother rubbing that in your face. I haven't had the same experience yet, although I can imagine I will someday.

This is essentially the territory that I hope to cover in my mammoth book. You are working your way through the same reading list that I am. I look forward to reading your review of Stanley Hedeen's "Big Bone Lick" before I pay retail for it.

If you haven't yet read Rudwick's "The Meaning of Fossils," you should. It's really the indispensable overview of the evolving ideas of extinction and evolution. Incidentally, it was written before you were born, but apparently none of his nuance about Cuvier or Lamarck appears to have made it into the high school history of science narrative yet. Another, even older, overview is John C. Greene's "The Death of Adam."

A nice bit of trivia: while the mammoth and mastodon were the slam dunk evidence for the idea of species extinction, later on they would be brought up as an argument against evolution by natural selection. The argument was that the persistence of the basic elephant forms through ice ages and warmer times showed that mere environmental changes couldn't cause major changes in species. Some more profound force must be involved. It didn't occur to them that the basic elephant form was just a well-adapted, all-purpose beast.

Lamarck was the official whipping boy of evolutionary science

Lamarck really doesn't get the credit he deserves. Everyone remembers his mistaken theory of evolution, but he actually made another contribution to biology that, in my opinion, makes him one of the most influential biologists ever - he invented the dichotomous identification key.

Are you going to review Mayor's book? I'd be interested in hearing what it was about and what you thought of it.