and Hidden Agendas
While most astrobiologists are upbeat about finding all kinds of life in the universe, a minority have their doubts. According to this skeptical school, our planet is so special that all but the simplest of organisms are likely to be uncommon elsewhere. Although many of the arguments on both sides are new, the debate about the uniqueness of Earth is as old as civilization. What's more, just as the debate in earlier times was by no means purely scientific, neither is it today.
The idea that our planet may be biologically almost unique was put under the spotlight by Rare Earth: Why Complex Life is Uncommon in the Universe, a book by Peter Ward and Donald Brownlee, a paleontologist and astronomer, respectively, at the University of Washington in Seattle. First published in January 2000, Rare Earth is a polemic for the view that whereas microbial life is likely to be widespread on other worlds, multicellular organisms—and intelligent life in particular—will prove to be scarce. The book has sold well, attracted an unusual amount of media attention, and has provoked comment and controversy among scientists and non-scientists alike. As its reviewer in the New York Times pointed out, "Rare Earth ... is producing whoops of criticism and praise, with some detractors saying that the authors have made their own simplistic assumptions about the adaptability of life forms while others call it 'brilliant' and 'courageous."' The Times of London wrote, "If they are right it could be time to reverse a process that has been going on since Copernicus."