Inspired by the controversy, in 1796 Cuvier wrote a landmark paper, Note on the Species of Living and Fossil Elephants, in which he put forward for the first time a formal theory of extinctions. His belief was that from time to time the Earth experienced global catastrophes in which groups of creatures were wiped out.

在那场争论的启发之下，居维叶于1796年写了一篇具有划时代意义的论文《关于活着的象和变成化石的象的说明》。在这篇论文里，他第一次正式提出了绝种的理论。他认为，地球不时经历全球性的灾难；在此过程中，一批批的生物彻底死亡。

For religious people, including Cuvier himself, the idea raised uncomfortable implications since it suggested an unaccountable casualness on the part of Providence. To what end would God create species only to wipe them out later? The notion was contrary to the belief in the Great Chain of Being, which held that the world was carefully ordered and that every living thing within it had a place and purpose, and always had and always would. Jefferson for one couldn't abide the thought that whole species would ever be permitted to vanish (or, come to that, to evolve).

对于宗教人士来说，包括居维叶本人，这种看法具有令人不快的含义，因为这意味着上帝是捉摸不定的，莫名其妙的。上帝创造了物种，然后又消灭这些物种，他究竟要干什么？这种看法跟“大生物链”的信念绝对相反。那种信念认为，世界是精心安排的，世界上的每种生物都有一定位置，都有一个目的，过去从来就有，将来也总是会有。杰斐逊无法接受这种看法：整个物种有朝一日会消亡（或者会到那种地步，会演变）。

So when it was put to him that there might be scientific and political value in sending a party to explore the interior of America beyond the Mississippi he leapt at the idea, hoping the intrepid adventurers would find herds of healthy mastodons and other outsized creatures grazing on the bounteous plains. Jefferson's personal secretary and trusted friend Meriwether Lewis was chosen co-leader and chief naturalist for the expedition. The person selected to advise him on what to look out for with regard to animals living and deceased was none other than Caspar Wistar.

因此，当有人问他，派个考察队去密西西比河以里的美国内地进行考察有没有科学和政治价值的时候，他马上肯定了这个建议，希望勇敢的探险家们会发现一群群健康的乳齿象和别的超大动物在富饶的平原上吃草。杰斐逊的私人秘书和知心朋友梅里韦瑟·刘易斯被选定和威廉·克拉克一起担任领队，而且还是这次远征的首席博物学家。被选定来指点他该找什么活的动物和死的动物的不是别人，正是卡斯帕·威斯塔。