Tuesday, May 29, 2007

Oldest Life on Earth


A Canadian-led team of scientists has discovered what they say is the oldest indisputable evidence of life on Earth -- the fossilized trackways of slithering microbes in a 3.35-billion-year-old rock from Australia.

The team, led by University of Western Ontario geologist Neil Banerjee and including three scientists from the University of Alberta, claims to have completed the first "direct dating" of a biomarker from the planet's earliest epoch. Previous studies -- including one led by Banerjee in 2004 that fixed a 3.5-billion-year-old age to fossilized microbe trails found in South Africa -- have been criticized for relying on techniques that dated surrounding rock rather than the "ichnofossil" tracks themselves.

Banerjee said Monday the dating of the Australian fossils is "quite unique" because the researchers used a state-of-the-art, laser-plasma mass spectrometer at the U of A to precisely target tiny minerals and organic residues captured inside the microbes' primordial burrows.

"One of the criticisms of our earlier work was based on the analogy that just because the London Underground was dug into million-year-old rock, that doesn't make the Underground a million years old," said Banerjee. "This time, we dated the fossil itself. To our knowledge, this is the first time anyone has directly dated an archean microfossil."


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