Rather, life grew here on Earth for about half the age of the galaxy before we humans even knew that the sun was a star among the stars. Our single species itself was five hundred centuries old before we knew our place in the sky. Reflection has led me to argue that we had to number on the order of a billion thinking human beings before our earth could become home to such devices as sensitive microwave receivers, longer still for the alternatives. Technology is a social phenomenon spread among billions whose diverse lifework led to what we now can do. IQ does not alone create means for detecting signals from the stars.
Intelligence is necessary but it is insufficient.
That tentatively defines the time scale. Without a synchronizing feature we do not notice at all in the Galaxy, we cannot expect a good match to our quite new status, for we have known of radio astronomy for less than one century out of all earth history. One sees at once that detectable counterparts are likely to be ahead of our level of technology, while the rest of them, still silent and undetectable, are far behind on the human scale of time. What we see as possible is an ambitious project, old by any human standards, defined by a timescale we do not know, undertaken perhaps intermittently by some curious, effective, but by no means all-powerful, species of billions of beings of our technological kind dwelling somewhere out there among the many, many stars. They too must pay the energy bills and await an answer, perhaps not for the first time.