UNIVERSITY OF MINNESOTA PRESS, APRIL 2013“It takes one to know one”—this schoolyard retort has thus far guided the search for extraterrestrial intelligence (SETI), and the belief is reinforced by countless science-fiction portrayals of aliens as humanoids. Is it possible that cosmic evolution has converged on bipedal, big-headed forms looking somewhat like us and having their run of a bevy of Earth-like planets? If so, where are they? Why haven’t they, like us, broadcast their presence across the electromagnetic spectrum, contacting their brothers across the stars and mitigating our cosmic loneliness?

I ponder these questions and more in my new book, Cosmic Apprentice: Dispatches from the Edges of Science.

SETI is complicated by the fact that intelligence is multiple and the possibility  that the search for extraterrestrial intelligence is a replacement for religion in a secular age. Instead of believing in a god who made us in...

Even great scientists fall prey to this anthropocentric and zoocentric tendency to imagine extraterrestrial intelligence as a reflection of ourselves in a cosmic distorting mirror. Stephen Hawking warns not only that aliens probably exist but also that we must be careful of broadcasting our presence because, if they find us, they may eat us. But wouldn’t aliens able to navigate the vast distances of interstellar space have the technical capacity to synthesize food directly from interstellar matter? Traversing the universe for a human snack makes about as much sense as booking a supersonic jet to Morocco to eat a single garbanzo bean. In contrast, physicist Michio Kaku speculates any aliens likely to arrive on Earth will be less like Christopher Columbus and company destroying Native American populations (as Hawking suggested) and more like the United States’s experience during the Vietnam War: one of conflict with no benefit, with the aliens ultimately hightailing it back to the stars whence they came.

Both of these scenarios show the difficulty Earthlings have imagining aliens who are truly alien: they always seem to take the form of thinly disguised versions of ourselves, slightly different races, perhaps human subspecies. Part of the problem is that it is hard for us to imagine communicating with beings that are too different from ourselves. At the end of Contact, written by my late father Carl Sagan, the aliens project themselves as humans in order to communicate with us. In Stanislaw Lem’s Solaris, a planet with a living ocean beams images of familiar humans up to a human crew orbiting above. Lem’s “solution” to the science-fiction depiction of aliens underscores the depth of our interspecies communication problem.

I have an admiration for science but recognize it as a fallible human expression of a greater planetary intelligence that remains in some ways more alien to us than anything we seek in the stars. Life-forms—including our own bodies—generally regulate unchecked growth. But the unchecked growth and technological innovation of our civilization are causing problems of global pollution, starvation, war, and climate change. Ultimately, exponential growth, whether of spreading pathogens that kill their hosts, of the stem cells in our own bodies, or of our own technoscientific civilization, is unsustainable. Is a typical plateau in the growth of even the most advanced technical civilizations, including abandoning SETI efforts to address problems at home, the reason why we don’t see aliens? As physicist-cum-theoretical-biologist Josh Mitteldorf shows, aging itself looks like a genetic adaptation for regulating population—steady death rates keep ecosystems in balance, lessening the likelihood of populations booming to the point where they get wiped out by starvation and disease.

The search for life elsewhere continues to be a worthy scientific endeavor, but the greatest benefits to our species may lie in a renewed examination of terrestrial intelligence here at home.

Dorion Sagan, son of astronomer Carl Sagan and biologist Lynn Margulis, is an award-winning writer, editor, and theorist. His writing has appeared in The New York Times, Wired, Natural History, and other publications. Read an excerpt of Cosmic Apprentice.

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