  The intuition suggested by the Drake equation implies that technology should
be less prevalent than biology in the galaxy. However, it has been appreciated
for decades in the SETI community that technosignatures could be more abundant,
longer-lived, more detectable, and less ambiguous than biosignatures. We
collect the arguments for and against technosignatures' ubiquity and discuss
the implications of some properties of technological life that fundamentally
differ from nontechnological life in the context of modern astrobiology: It can
spread among the stars to many sites, it can be more easily detected at large
distances, and it can produce signs that are unambiguously technological. As an
illustration in terms of the Drake equation, we consider two Drake-like
equations, for technosignatures (calculating N(tech)) and biosignatures
(calculating N(bio)). We argue that Earth and humanity may be poor guides to
the longevity term L and that its maximum value could be very large, in that
technology can outlive its creators and even its host star. We conclude that
while the Drake equation implies that N(bio)>>N(tech), it is also plausible
that N(tech)>>N(bio). As a consequence, as we seek possible indicators of
extraterrestrial life, for instance, via characterization of the atmospheres of
habitable exoplanets, we should search for both biosignatures and
technosignatures. This exercise also illustrates ways in which biosignature and
technosignature searches can complement and supplement each other and how
methods of technosignature search, including old ideas from SETI, can inform
the search for biosignatures and life generally.
