Thank you for sending me to Scientific American's Web site. There, in addition to the pieces you mentioned, I found Ian Crawford's article on extraterrestrial intelligence called "Where are they?" Again, this reverberated with several things we have been batting back and forth, not only the little green men who make crop circles and precision-cut cattle, but also the idea that life arose here so surprisingly soon after the formation of the earth. As Crawford points out, this seems to imply that life is inevitable on planets with the right conditions, which only deepens the "Fermi paradox"--that statistically, ETs should be common, but since they haven't turned up or sent any signals, they obviously are not common.
Apparently, Paul Horovitz calculates that there should be a million suitable solar systems within 1,000 light years, and if just one of those has a radio-transmitting civilization then there will be 1,000 civilizations in the whole galaxy, or--if each lasts 1,000 years--there have been 12 billion civilizations altogether. So why do we still have to make our own crop circles?
Crawford's resolution of the paradox is that life may be near-inevitable, but multi-cellular life is not. It took 3 billion years to crop up here. And intelligent life took another 700 million years. It might have taken less time if the meteorite hadn't knocked out some promising dinosaurs, but even that argument is thin, because the meteorite missed the brightest dinosaurs of all--the birds--and they have hardly done much to invent radio and spacecraft in the intervening 65 million years.
I differ from Crawford in one particular, however. He describes the appearance of intelligence as a contingent fluke, based on Stephen Jay Gould's random-walk hypothesis. But Gould is wrong about this, I think, as Bob Wright has convincingly demonstrated in part of his book Nonzero. There is a progressive element to some kinds of evolution, and human intelligence is a kind of destiny, not just a fluke. Brains get bigger because of evolutionary arms races--predator vs. prey or male vs. female trying to outwit each other--and this produced steady, incremental progress in the brain size of big mammals during the entire Tertiary, as Leigh van Valen first demonstrated. Van Valen coined the term "Red Queen" for this process, after Alice's friend in Through the Looking Glass who runs buts stays in the same place: a predator gets faster or cleverer, but so does its prey, etc. This dynamic would seem to drive at least some species towards sufficient braininess to invent radio. After all, the dolphins, elephants, crows, and octopi are not that far behind us in the intelligence stakes.
So, George, tell me: Where are they?