Wallace proposed the first evolutionary theory of aging. He stated that if too many people lived for a long time they would compete for resources needed for other members of the species that were of reproduction age.

Wallace's paragraph briefly expressing this idea was published by the editor of the translation, Edward B. Poulton, as a footnote on p. 23 with this comment: "After reading these proofs Dr. A.R. Wallace kindly sent me an unpublished note upon the production of death by means of natural selection, written by him some time between 1865 and 1870. The note contains some ideas on the subject which were jotted down for further elaboration, and were then forgotten until recalled by the argument of this Essay. The note is of great interest in relation to Dr. Weismann's suggestions, and with Dr. Wallace's permission I print it in full below."

(Thanks to Tim Opler for this reference.)

By “amphimixis” Weismann meant the union of the two parent germs, which he considered the principal source of heritable variation in evolution by natural selection. English translation in Weismann’s Essays upon Heredity, Vol. 2, Oxford, 1892.

Weismann produced experimental evidence that acquired characters are not transmitted.

Weismann elaborated the theory of the continuity of the germ plasm. English edition, 1893.