The Mystery of Extinction
A hundred years ago the French scientist Cuvier, who gave much time to the study of the fossils of extinct mammals, presented the “cataclysmal” explanation of their end. They were destroyed by sudden great geologic changes. To us, perhaps, these changes seem to have ignored certain other animals in a most disquieting way. Cuvier was at a disadvantage, of course, for he was working in a Bible-ridden world which had to accept the Book of Genesis as fact. Even as late as 1887, Henry H. Howorth wrote in The Mammoth and the Flood:
These facts ... prove in the first place that a great catastrophe or cataclysm occurred at the close of the Mammoth period, by which that animal, with its companions, were overwhelmed over a very large part of the earth’s surface. Secondly, this cataclysm involved a very wide-spread flood of water, which not only killed the animals but also buried them under continuous beds of loam or gravel. Thirdly, that the same catastrophe was accompanied by a very great and sudden change of climate in Siberia, by which the animals which had previously lived in fairly temperate conditions were frozen in their flesh underground and have remained frozen ever since.[24]
In the hundred years since Koch found a mammoth and a spear point in Missouri we have learned little that is definite about the reasons for the extinction of mammoth, mastodon, camel, horse, sloth, and the rest. We merely know that they died out as the glaciers began to melt. The most natural guess for either scientist or amateur is that change of climate was the lethal factor. Yet we know that many of them had already survived drastic changes of climate and lived through interglacials as well as glacials in the Great Ice Age. Further, how do we account for the survival of deer, antelope, fox, rabbit, moose, beaver, bear, and so many other animals? How could climate be so selective? If the dire wolf died, why not the timber wolf? If the short-faced bear, why not the grizzly? If one form of rabbit and three forms of antelope, why not all rabbits and all antelopes? If disease instead of climate was the great eliminator—as some have suggested—we face the same dilemma.
The mysteries of extinction are so many and so baffling that it is small wonder no book in English has been written on the subject. Since 1906, when Henry Fairfield Osborn summed the matter up in his paper of fifty-odd pages, “The Causes of Extinction of Mammalia,” Eiseley credits only two theories with contributing anything new to the discussion.
One is the hypothesis of Sewall Wright and his co-workers that when an animal was greatly reduced in numbers it would suffer fatally from inbreeding.[25] This, however, leaves us still searching for what reduced its numbers so radically.
The other theory is Sauer’s: Man, the hunter, destroyed the larger, clumsier, and more gregarious animals largely by means of fire drives, and these fires made the grasslands.[26] Or, at least, the fire drives “broke the back” of mammalian resistance.[27] Eiseley objects on a number of grounds. It was not alone the large, clumsy, and gregarious animals that disappeared. Certain mollusks, a variety of toad, a subfamily of rabbits, the dire wolf, the saber-toothed tiger, three forms of antelope, the short-faced bear, and a small horse also disappeared. More damaging still to Sauer’s theory is the fact that a number of birds became extinct. Eiseley asks, “Why, if this method was so deadly, did the living bison and the living antelope roam the plains in countless numbers?” He points out that, while there is abundant evidence of extinct bison caught and killed in fire drives, there is no proof of mass kills of mammoth, horse, camel, and antelope.[28] He also mentions the mastodon, the giant beaver, and the sloth, which frequented eastern forests or northern bogs and died in them. “Though man was on the scene at the final perishing, his was not ... the appetite nor the capacity for such gigantic slaughter.”[29] Though Sauer believes that the numbers of hunting man in the New World were comparatively large when he killed Bison antiquus, most authorities disagree. Alfred S. Romer believes that if man had been numerous enough and deadly enough to play a major part in the killing, we should find more evidences of his association with the extinct mammals.[30]
Romer and Edwin H. Colbert have put forward another explanation for the extinction of the mammals. They suggest that the advent of man in the New World may have upset a nicely balanced state of nature.[31] But man had been living with just such animals in the Old World for hundreds of thousands of years before they became extinct. What, then, destroyed the mammoth in Europe?
The most pulling of all the fossils of extinct animals are those in the deep Alaska muck beds. Their numbers are appalling. They lie frozen in tangled masses, interspersed with uprooted trees. They seem to have been torn apart and dismembered and then consolidated under catastrophic conditions. Eden and Plainview spear points and perhaps one Clovis have been found in these chill beds. Skin, ligament, hair, flesh, can still be seen.[32] If scientists can solve this mystery before the high-pressure water stream of the miner disperses the evidence, perhaps we shall be nearer solving one of the greatest and most tantalizing problems involved in the story of early man—the date of the extinction of the great mammals.
This problem of when the mammoth died should have puzzled the Old World as well as the New and caused us to question the dating of Neanderthal and Cro-Magnon quite as much as Folsom man. Oddly enough, it did nothing of the kind. In Europe the mammoth was accepted as diagnostic of the glacial period. The fact that a Magdalenian man of southern France sketched a mammoth on the wall of a cave proved that the man existed in the Great Ice Age. But in America, if a spear point turned up with the bones of a mammoth, too many anthropologists accepted it as proof that the animal died after the ice fields had melted. The mammoth proved the antiquity of man in Europe; man proved the modernity of the mammoth in America. The only shred of evidence to support such reasoning was the questionable pottery and coal that lay beside the mastodon bones in Ecuador. We should have had more and better proof, and we are beginning to get it.