Newspaper article The Christian Science Monitor

Rocks of Ages Yield Clues to Life's Start

Newspaper article The Christian Science Monitor

Rocks of Ages Yield Clues to Life's Start

Article excerpt

Wielding a unique high-tech probe to explore slices of ancient rock, scientists have found the oldest evidence yet of primitive life on Earth.

The discovery pushes back by at least 300 million years the earliest known traces of living organisms. The results also suggest that the tiny life forms were hardy enough to withstand a punishing meteor bombardment Earth endured more than 3.8 billion years ago, the researchers say. The meteor onslaught is thought to have sterilized the young planet.

As scientists gain more experience with the new probe, it could help provide details on living conditions for microbes on early Earth and offer a more precise means of unearthing geochemical signs of past life in meteorites. "Our evidence establishes beyond a reasonable doubt that life {on Earth} emerged at least 3.85 billion years ago," says Stephen Mojzsis, a graduate student at the Scripps Institution of Oceanography in La Jolla, Calif., and lead author of a research paper in the latest issue of Nature. "We may well find that life exists even earlier." Until now, 3.5 billion-year-old bacteria fossils found in western Australia represented some of the earliest evidence for life on Earth. William Schopf, a paleobiologist with the Center for the Study of Evolution and the Origin of Life at the University of California at Los Angeles (UCLA), discovered and analyzed these fossils over a seven-year period and reported his results in 1993. He uncovered eight new species and noted that the microbes' diversity and physical complexity suggested that their ancestors must have been much older than 3.5 billion years. The evidence Mr. Mojzsis's team uncovered comes not from fossils, but from the chemical makeup of samples taken from a 3.85 billion-year-old rock formation on Akilia Island, off of southern West Greenland. The samples, once ancient ocean sediment, changed dramatically under immense pressure and searing temperatures born of geological change. …

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