New studies of the world's most primitive living things - colonies of bacteria found on the Western Australia coast - suggest that life on Earth may have begun much earlier than the accepted date of about 3.5 billion years ago.
The colonies build rock-like structures, known as stromatolites, in tidal pools at Shark Bay: research has revealed that they are comparable with ancient stromatolite fossils found in the nearby Pilbara region, which are the oldest convincing evidence of life.
Sophisticated investigations by a team at the UNSW Australian Centre for Astrobiology (ACA) have now revealed that the colonies are very biologically diverse - involving many more than just a few species as previously thought - and that the same was probably true of the 3.5 billion-year-old Pilbara stromatolites.
"Powerful new chemistry and genomic tools have revealed that the Shark Bay stromatolites have remarkable biodiversity, with evidence so far of more than 100 species of bacteria," says ACA Deputy Director Professor Brett Neilan.
"In effect, this suggests that by 3.5 billion years ago Earth was already teeming with diverse microbial life. If this is so, evolution must have already been going on for a long time. We can't be sure, but certainly many tens of millions of years earlier. These findings could reset the start of the clock of life."
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