A Short History of Panspermia from Antiquity Through the Mid-1970s

Panspermia is the philosophical proposition that the precursors of life are present in space and able to initiate life on reaching a suitable environment (especially the Earth). Only in the past century has the subject advanced from the lowly status of a dreamy hypothesis to a vibrant new science that is testable and observable. This history of panspermia presents the major figures associated with such hypotheses. It examines their motives, methods, and arguments, situated when possible in their historical context and culture rather than their impact on the present. From antiquity to the early modern period (1500-1800), the debates on the plurality of worlds and panspermia overlapped considerably. In the later modern period (1800 to the present), the narrative thread interweaves panspermia with the origin of life and the theory of evolution, and we can see authentic inputs from scientists rather than philosophers. In the interests of concision, I have omitted topics such as the Search for Extraterrestrial Intelligence, the exploration of the solar system by probes and landers, planetary protection (the inverse of panspermia), and the discovery of exoplanets. The historical literature is sometimes confusing: to correct for that, I have personally examined the original sources of every work cited rather than simply accepting the published findings of other scholars at face value.