"study of decadence" in a species, etc., 1876, from Greek gēras (genitive gēratos) "old age" (see geriatric) + -logy. Related: 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]