David Brin criticizes the possibly reckless turn in recent SETI research. He also speculates on what the great silence may say about human societies. It may not be such a good idea to go about shouting to the cosmos - not when we have so little idea of what may be out there.

That said, Brin speculates on the nature of any intelligent life we are likely to meet. He notes that our scientific and technological society is very unusual when compared to societies of the past: It is, he says, diamond-shaped, with relatively few at either the bottom or the top, and with a broad equality of social station, rights, and even wealth in the middle. Maintaining such a society is hard work, and one reason we seem to be alone in the universe may simply be that very few alien civilizations have escaped from feudalism or something like it.

Robin Hanson runs a cost-benefit analysis on our use of very loud radar signals. He finds that if there is even a small probability of a hostile civilization hearing us, then the risks are not worth the rewards. This conclusion holds up under fairly severe assumptions, and it grows much firmer as we consider our likely technological developments in the near future. Astronomy, moreover, is advancing rapidly, and it will likely tell us much more about the probability of existence and the nature of extraterrestrial life. When it does, we may have a better idea of the wisdom of sending out very loud radio signals. In the meantime, he concludes that yes, humanity should indeed shut the hell up.

We have few tools at our disposal to learn about intelligent extraterrestrials - if they even exist. But one relatively powerful tool is evolutionary psychology. Jerome H. Barkow reviews some findings from terrestrial evolutionary psychology and considers their implications for alien life. We will learn a lot if we can discover what aliens find sexy, he claims - because sexual selection has overwhelmingly influenced terrestrial animals, including ourselves.

We will also learn a great deal by observing aliens’ predation history, their group cooperation, and their genetic transmission of culturally favored traits. Of course, these observations will have to wait for first contact. Barkow concludes by agreeing with Robin Hanson - until we know more, humanity should probably keep relatively quiet.

Douglas Vakoch argues that active SETI is not to be feared: If highly advanced civilizations exist out there, they will have highly advanced radio detection equipment. If they are anywhere near us, then they will have known about us for decades. Messaging them can do no more harm than what we have already done, and it may do us a great deal of good, particularly if these civilizations are waiting for us to make the first move, and if messaging them directly is the signal they need to initiate contact.