在那場爭論的啟發(fā)之下,居維葉于1796年寫了一篇具有劃時代意義的論文《關于活著的象和變成化石的象的說明》。在這篇論文里,他第一次正式提出了絕種的理論。他認為,地球不時經歷全球性的災難;在此過程中,一批批的生物徹底死亡。
For religious people, including Cuvier himself, the idea raised uncomfortable implications sinceit suggested an unaccountable casualness on the part of Providence. To what end would Godcreate species only to wipe them out later? The notion was contrary to the belief in the GreatChain of Being, which held that the world was carefully ordered and that every living thingwithin it had a place and purpose, and always had and always would. Jefferson for one couldn'tabide the thought that whole species would ever be permitted to vanish (or, come to that, toevolve).
對于宗教人士來說,包括居維葉本人,這種看法具有令人不快的含義,因為這意味著上帝是捉摸不定的,莫名其妙的。上帝創(chuàng)造了物種,然后又消滅這些物種,他究竟要干什么?這種看法跟“大生物鏈”的信念絕對相反。那種信念認為,世界是精心安排的,世界上的每種生物都有一定位置,都有一個目的,過去從來就有,將來也總是會有。杰斐遜無法接受這種看法:整個物種有朝一日會消亡(或者會到那種地步,會演變)。
So when it was put to him that there might be scientific and political value in sending a party toexplore the interior of America beyond the Mississippi he leapt at the idea, hoping theintrepid adventurers would find herds of healthy mastodons and other outsized creaturesgrazing on the bounteous plains. Jefferson's personal secretary and trusted friend MeriwetherLewis was chosen co-leader and chief naturalist for the expedition. The person selected toadvise him on what to look out for with regard to animals living and deceased was none otherthan Caspar Wistar.
因此,當有人問他,派個考察隊去密西西比河以里的美國內地進行考察有沒有科學和政治價值的時候,他馬上肯定了這個建議,希望勇敢的探險家們會發(fā)現(xiàn)一群群健康的乳齒象和別的超大動物在富饒的平原上吃草。杰斐遜的私人秘書和知心朋友梅里韋瑟·劉易斯被選定和威廉·克拉克一起擔任領隊,而且還是這次遠征的首席博物學家。被選定來指點他該找什么活的動物和死的動物的不是別人,正是卡斯帕·威斯塔。