We're Now Pretty Certain Life on Earth Is 3.5 Billion Years Old

The Earth is 4.5 billion years old. But what about the life that exists on it? We've thought since 2006 that biological activity in the form of stromatolites—ancient layered geological structures—first appeared here 3.5 billion years ago, and now we have even more evidence to prove it.

Scientists took to the Strelley Pool Formation in Australia to check out the sulfur some rock formations that got there as a result of biological activity. They've looked at these deposits before, but this time they analyzed them through a different technique—analyzing the distribution of isotopes in each layer rather than on the whole—and their findings corroborated previous conclusion. Ars Technica explains:

Many of the differences were associated with inclusions of organic material within the rock. Similar values were found in iron-sulfur compounds that had precipitated out. The large positive values, the authors suggested, are an indication that the original source of the sulfur was probably from the atmosphere, consistent with what we know of its likely composition during the Archean era.

It seems life might not just be older than dirt, but as old as rocks. [Ars Technica]

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