Fossils Boost Life Origins Theory

By JEFF BARNARD Associated Press Writer JUNE 08, 2000 - Researchers have found what they believe are fossils 3.2 billion years old, suggesting that life on Earth originated in volcano-heated ocean depths where sunlight never entered. "The cradle of life may have been a sulfurous, subterranean inferno, not unlike a medieval vision of hell,'' said Birger Rasmussen, a paleobiologist at the University of Western Australia who reported the find in today's issue of the journal Nature. The formations, believed to be single-celled organisms, were found in Australian rock and are 600 million years younger than the earliest chemical evidence of life on Earth. But the find pushes back by some 2.7 billion years the fossil evidence of microbes living around hot springs at the bottom of the sea. The formations appear to be threadlike organisms, measuring a thousandth of a millimeter in diameter and a tenth of a millimeter long. They would have gotten their energy from chemicals like sulfur, rather than sunlight, Rasmussen said. "Deep beneath the ocean, hot springs would have been attractive habitats for primitive microbes, protected from the effects of early planetary bombardments, and bathed in a rich brew of metals and nutrients,'' Rasmussen said. "Such environments could have provided a safe setting for life hundreds of millions of years before Earth's surface was habitable.'' The findings do not settle the debate about how life started on Earth. The microbes could have migrated from somewhere else. But Rasmussen makes a compelling case that volcanic rocks out of reach of sunlight and bathed in boiling water may well have been the place it all began, said Andrew Knoll, a professor of paleobiology at Harvard University. "That medieval vision of hell is very much the current theory of biology,'' Knoll. Charles Darwin theorized that life may have started in a little pond warmed by sunlight. In the 1950s, scientists demonstrated that a bolt of lightning through a mixture of gases thought to simulate Earth's early atmosphere produced amino acids, a building block of life. Lately, however, biologists looking for the cradle of life have concentrated on places where hot water circulates through the Earth's crust. Rasmussen said he stumbled on the fossils while examining rock cores, consisting mostly of quartz and fool's gold, that had been drilled hundreds of yards below the surface. He was trying to figure out how much oxygen was in the early atmosphere. The spot is known as the Sulfur Springs deposit, situated in the Pilbara region of western Australia. Once an ancient seabed, the region now is rugged, rocky and hot, with little rainfall. "After looking at hundreds of slides, I noticed some unusual structures that contained a dense assemblage of intertwined filaments,'' he said. "After careful examination, I came to the conclusion that the filaments had to be biological.'' Knoll agreed. The filaments are regular in size, and in alignment. Besides adding to the picture of early life on earth, the fossils point the way for scientists looking for life elsewhere in the solar system, Rasmussen and Knoll said.