Don't Look for Aliens— Look for Their Robots

Scientists searching for extraterrestrial life should make sure to look for robot agents of the aliens, says a leading SETI astronomer. The search for life outside earth has so far focused on identifying the building blocks of biochemistry, following the assumption that aliens would meet our definition of "alive." Seth Shostak of the Search for Extraterrestrial Intelligence Institute in California thinks it's reasonable to assume that life forms would quickly develop machines to aid them, reports the Telegraph.

“If you look at the timescales for the development of technology, at some point you invent radio and then you go on the air and then we have a chance of finding you," Shostak wrote in the journal Acta Astronautica. “But within a few hundred years of inventing radio—at least if we're any example—you invent thinking machines.” He expounds on his theory here in the Guardian.
(More extraterrestrial life stories.)