4.1-billion-year-old crystal may hold earliest signs of life | Science News

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4.1-billion-year-old crystal may hold earliest signs of life

Life on Earth appeared before 4.1 billion years ago, new research suggests. This zircon crystal contains a small carbon impurity (indicated by arrow) associated with living organisms.

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New evidence suggests that life on Earth arose before 4.1 billion years ago, 300 million years earlier than previous estimates.

The oldest known fossils date back  to around 3.5 billion years ago, so scientists use other clues in the search for early signs of life (SN: 2/8/14, p. 16). Lifeforms preferentially stockpile carbon-12 in their cells, so any ancient substance enriched with carbon-12 could have a biological origin.

Researchers report the discovery of a 4.1-billion-year-old zircon crystal containing a carbon-12-laden impurity. Ancient carbon-containing zircons from this time period are extremely rare — only around one in 10,000 crystals — so the finding will be difficult to confirm, the researchers note October 19 in the Proceedings of the National Academy of Sciences.

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