Contact Optimists vs. Unique Earthers

Of the three fundamental questions asked by astrobiologists, the question of the second genesis of ETIL, is the one we ask next. We ask about the possibility that intelligent living creatures currently inhabit earthlike planets somewhere in the cosmos. To date no empirical evidence exists that extraterrestrial intelligence exists. Despite more than three decades of active SETI (Search for Extraterrestrial Intelligence) research, no radio or visual contact has occurred. If we rely solely on empirical evidence, then we have no reason to believe that anyone else is out there.

Space researchers are divided into two camps. The Contact Optimists contend that simple reasoning would suggest that the universe should be teeming with life. Those holding the Uniqueness Hypothesis, in contrast, suggest that the earth is probably the first and only home for a technological civilization. Until recently, the lack of empirical evidence combined with the high improbability of a repeat of earth’s evolutionary history seemed to give the edge to the uniqueness hypothesis, to the unique earthers (Brin, 1983).

The unique earth hypothesis depends on the assumption of the improbability that just the right prebiotic contingencies would fall into place to make the spring from non-life to life possible, and the low probability that the contingencies that made the evolution of intelligent life on earth could be repeated in sequence. Two of the most prominent evolutionary biologists, Stephen Jay Gould and Francisco Ayala (Gould 1989; Ayala 2004), have argued that if you replay earth’s evolutionary tape again and again, it will never produce the same result. “The chemical origin of life seemed to depend on such an improbable sequence of events, similar to throwing a die over and over and getting a six every time, that biologists were inclined to think that life elsewhere must be a very rare occurrence,” writes David Darling (Darling 2001, p.121).

Contact optimists, while recognizing the improbability problem, counter with the idea of big numbers. Because the number of possible locations in this vast universe for evolution to get started is so large, the number of possible repeats of earth’s biological history is also large. In contrast to the unique earth biologists, contact optimism has grown among astronomers. “Most of the speculation about life in the universe came from astronomers, who were generally positive about the idea simply because they thought there were probably so many planets around. With billions of potential homes, surely life couldn’t be that scarce,” comments Darling (Darling 2001, p.121). He concludes, “Almost beyond doubt, life exists elsewhere” (Darling 2001, p.xi).

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