Life on Earth may have begun 300m years earlier than previously thought
Discovery, if confirmed, indicates that living organisms appeared on Earth 4.1 billion years ago, remarkably soon after its formation
Living organisms may have existed on Earth as long as 4.1bn years ago – 300m years earlier than was previously thought, new research has shown.
If confirmed, the discovery means life emerged a remarkably short time after the Earth was formed from a primordial disc of dust and gas surrounding the sun 4.6bn years ago.
Researchers discovered the evidence in specks of graphite trapped within immensely old zircon crystals from Jack Hills, Western Australia.
Atoms in the graphite, a crystalline form of carbon, bore the hallmark of biological origin. They were enriched with 12C, a “light” carbon isotope, or atomic strain, normally associated with living things.
It suggests that a terrestrial biosphere had emerged on Earth as early as 4.1bn years ago, said the scientists writing in the journal Proceedings of the National Academy of Sciences.
The US scientists, led by Dr Mark Harrison, from the University of California at Los Angeles, said the graphite was completely encased in zircon that was crack-free and could not have been contaminated despite the passing of aeons.
They wrote: “This study extends the terrestrial carbon isotope record around 300m years beyond the previously oldest-measured samples from south-west Greenland.”
Some non-biological processes could also produce the light form of carbon, notably meteorite impacts, said the researchers.
But the amount of extra-terrestrial carbon needed to account for the findings made meteorites an unlikely source.
“A biogenic origin seems at least as plausible,” the scientists added.
Confirming the connection with early life would represent “a potentially transformational scientific advance” they said.