2.6-Billion-Year-Old Carbon May Be Oldest Remains of Life on Land

Remnants of organic matter in soil collected in South Africa indicate that microorganisms had moved from the Earth’s oceans onto land at least 2.6 billion years ago, according to researchers from Pennsylvania State University. Although life has been known to exist in the oceans for at least 3.8 billion years, the oldest known remnants on land, found in Arizona, were only 1.2 billion years old.

Geochemist Hiroshi Ohmoto and his colleagues report in today’s Nature that the samples were collected in Mpumalanga province and were found between two rock layers, one known to be 2.6 billion years old and the second 2.7 billion years old. Studies showed that the most likely source of the carbon molecules they found was large mats of bacteria.

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--Compiled by Times medical writer Thomas H. Maugh II