Oldest ever domains of life co-existed as early as 2.7 billion years ago

Scientists at the University of Illinois at Chicago have found direct evidence that the three known domains of life - eukaryotes, bacteria, and archaea - coexisted at least as long as 2.7 billion years ago.

Washington, Aug 21 : Scientists at the University of Illinois at Chicago have found direct evidence that the three known domains of life - eukaryotes, bacteria, and archaea - coexisted at least as long as 2.7 billion years ago.

Present theories state that they went their separate ways around three billion years ago, and until now scientists had been unable to pin down the time of that split.

Associate professor of earth and environmental sciences, Fabien Kenig and his former doctoral student Gregory Ventura, discovered lipid remains of archaea in shale samples deep in a Canadian gold mine near Timmins, Ontario, about 400 miles north of Toronto.

Analysis of the samples revealed a complex mixture of molecular fossils, "essentially made of archaea-derived lipids".

According to the researchers, the archaea lived in water and sediments when the sea covered the region. After burial, the archaea thrived where very hot water circulated in the rocks and where gold was deposited.

Later, shale containing fossilized archaea got buried under thousands of feet of volcanic rock and sediments, the scientists wrote in their study in the August 20-24 edition of the Proceedings of the National Academy of Sciences.

"Now we are sure the three domains of life were well separated and evolving (independently) by 2.7 billion years ago," said Prof. Kenig.

The finding broadens the known geographic reach of archaea during this time period, adding proof that the ancient organisms existed both in sedimentary environments and in subsurface hydrothermal settings, he said.

"Considering the extent and composition of today's deep biosphere, it is likely that such hydrothermal subsurface communities have existed for much of the Earth's history," the study said.

ANI