Technosignatures: A 400-Year History

Technosignature Science (TS), also known as astroarchaeology or SETA (Search for Extraterrestrial Artifacts), is a contemporary research programme which attempts to detect evidence of extraterrestrial intelligent life by identifying phenomena which may be explained only as the result of technological modification of a given environment (i.e. technosignatures). Examples of technosignatures include artificial satellites, atmospheric pollution, asteroid mining, as well as interstellar radio communications, which are the target of "classical" SETI. TS promises numerous potential developments in the near future; it also poses several interesting epistemological questions concerning the identification and assessment of technosignature-related evidence, which are starting to be explored by relevant literature in recent years. However, the debate concerning technosignatures has deep roots. Indeed, many of the questions facing astronomers today have direct precursors dating as far back as the XVII century. My talk will outline the history of the debate concerning what constitutes evidence when it comes to extraterrestrial intelligent life. I will offer examples of historical controversies and discussions concerning phenomena which were identified and described as technosignatures (from Kepler's oppida lunaria to Schiaparelli's 'canals' on Mars, and others). Finally, I will highlight some key epistemological and methodological points in these debates which are most relevant to contemporary discussions, hopefully helping to bring these questions into clearer focus for future research.