“物種衰落的研究”等，1876年，源自希臘語 gēras（屬格 gēratos）“老年”（參見 geriatric）和 -logy。相關詞彙： Geratologic。
I have adopted this new term with considerable hesitation and doubt, and have only done so under the pressure of necessity. In no other way can I better convey my conviction that there is a traceable correspondence between all manifestations of decline in the individual and in the group to which the individual belongs, which may, like embryology, be used inductively in reasoning upon the probable affinities of animals. [A. Hyatt, paper on "Genetic Relations of Stephanoceras," read June 7, 1876, published in Proceedings of the Boston Society of Natural History, vol. xviii, 1877]
我在極度猶豫和懷疑中採用了這個新術語，只是在必要的壓力下才這樣做。通過這種方式，我可以更好地表達我的信念，即個體和個體所屬的羣體中所有衰退表現之間存在可追溯的對應關係，這種關係可以像胚胎學一樣歸納地用於推理動物的可能親緣關係。[A. Hyatt，“Stephanoceras 的遺傳關係”論文，1876年6月7日讀，發表於《波士頓自然歷史學會議事錄》第18卷，1877年]
