But a new book by UW Professors Peter Ward and Donald Brownlee contends that, contrary to popular thought, we just might be alone and Earth might be unique, if not in the universe at least in this celestial neighborhood.
In Rare Earth, Ward and Brownlee examine the remarkable confluence of conditions and events that deposited life-forming chemicals on Earth, allowed simple life to gain a foothold, and then protected the planet sufficiently and created just the right environmental factors for advanced life to slowly evolve.
“It seems like something a lot of people don’t want to hear, yet nearly everyone who works in these areas has remarked at one time or another how unusual the Earth is, ” says Brownlee, an expert on comets, the space bodies that might have delivered the first organic chemicals and life-sustaining water to Earth. In fact, he and Ward, whose extensive research on the fossil record has provided key insights into prehistoric mass extinctions, frequently discuss the Earth’s unusual character with students in their astronomy and geological sciences classes.
The scientists don’t argue that life is rare. Recent evidence showing that simple microbial life can survive extreme conditions on Earth is an indicator that such life also might be widespread in the galaxy and the universe. “But you need to have a vast amount of time to let evolution ramp up to animals, and we think there are only a small number of planets where that could happen, ” explains Ward, who says the key is having near equilibrium in such things as temperature and water content over enormous time spans.
“The underlying theme of the book is that the Earth is a very charmed planet, ” says Brownlee. “We know of no other body that is even remotely like Earth.”
The authors may be as charmed as the planet. In February, after Rare Earth was featured as the centerpiece of the New York Times’ Science section, sales rocketed. Within hours, the book shot to the top ten on Amazon.com. Six months after publication, it remains among the top 200 sellers of the million or so books that Amazon sells.