> In summary, we're looking for ANCIENT Type III civilizations. Yes. This is because of the low probability that intelligent life develops somewhere else at ev

> In summary, we're looking for ANCIENT Type III civilizations. Yes. This is because of the low probability that intelligent life develops somewhere else at even close to the same time as it did on Earth. Our best understanding is that life has existed on Earth for something like 4 billion years, and complex life has existed for about 500 million. However, complex life capable of building spacecraft (or even radios) has only existed for a few hundred thousand (that is being extremely generous, of course), and only developed that technology in the last ~100 years. If intelligent life has or will evolve somewhere else in the universe, and progresses anything like it did here, then the odds seem overwhelmingly in favour of one of two scenarios: - It evolved millions of years ago, and if it has not wiped itself out, is virtually god-like by our standards due to its head start on technological development. - It has not yet evolved, or at best is the equivalent of primates or the proto-humans of several hundred thousand years ago.