Science / Medicine : Rapid Evolution of Life Theorized

NASA scientists proposed last week that it could not have taken more than 165 million years for the most fundamental forms of life to evolve on Earth--far less time than some had thought.

Based on studies of craters on the moon, Verne Oberbeck and his colleagues at the Ames Research Center in Mountain View, Calif., estimated that objects at least 150 miles in diameter slammed into Earth about every 165 million years. Impacts of that magnitude would have “sterilized” the surface of Earth, killing all developing life, he said.

That means it could not have taken longer than 165 million years for early chemical evolution to occur on Earth because any such life would have been destroyed every time one of these objects struck, Oberbeck said.

If the new, shorter estimate is correct, then the most fundamental forms of life can apparently evolve in less time than had been thought, said planetary scientist Christropher Chyba of Cornell University in Ithaca, N.Y. “If life evolves fast, then maybe it’s easy. And if the evolution of life was easy, then there’s great hope for it to have happened on other worlds as well,” he said.