“The Deadly Mission of Phineas Snodgrass,” Frederik Pohl, 1962 – (short short) Snodgrass travels back to Year One and to solve the world’s medical problems, only to create a population crisis that threatens to destroy all human life.
Comments: Read in 100 Great Science Fiction Short Short Stories. A response to L. Spraque De Camp’s Lest Darkness Fall.
Author: Wikipedia: “Frederik George Pohl, Jr. (born November 26, 1919) is an American science fiction writer, editor and fan, with a career spanning over seventy years — from his first published work, “Elegy to a Dead Planet: Luna” (1937), to his most recent novel, All the Lives He Led (2011).” Read by Geoffrey A. Landis at PodOmatic. See also io9’s article, “Great moments in alternate history: the non-fall of the Roman empire.”