There's now evidence that life on Earth began at least 3.5 billion years ago.
Scientists have confirmed this to be true from microfossils in a nearly 3.5-billion-year-old rock found in Western Australia.
Paleobiology professor J. William Schopf of the University of California-Los Angeles and geoscience professor John W. Valley of the University of Wisconsin-Madison led the study, conducting it along with other researchers from the UW-Madison and using technology from the research university's WiscSIMS Laboratory.
Life On Earth Existed 3.5 Billion Years Ago
Back in 1993, Schopf first described microfossils in the journal Science, identifying them based on their unique, cylindrical, and filamentous shapes. In 2002, he also published more evidence of the fossils' biological identities.
Now Valley and the other geoscientists at the University of Wisconsin-Madison used a secondary ion mass spectrometer or SIMS, also known as IMS 1280, to separate the carbon of every fossil into each one's isotopes. This allowed them to measure their ratios and conclude that the fossils have a biological origin as opposed to a mineral one.
"By 3.465 billion years ago, life was already diverse on Earth; that's clear — primitive photosynthesizers, methane producers, methane users. These are the first data that show the very diverse organisms at that time in Earth's history, and our previous research has shown that there were sulfur users 3.4 billion years ago as well," Schopf says.
These lifeforms are believed to have existed when there was little or no oxygen in the atmosphere, as Schopf thinks that advanced photosynthesis hadn't evolved yet. In fact, he says that oxygen would've killed these microbes.
The rock specimen is now stored in the London Museum of Natural History.
Coauthors of the paper include Kouki Kitajima and Michael J. Spicuzza of the University of Wisconsin-Madison and Anatoliy B. Kudryavtsev of the University of California-Los Angeles.
Oldest Fossil Debate Settled
Before this, a debate has been roaring on over the oldest fossils in existence, and this has been going on for more than 20 years already.
Particularly, Schopf's findings have been criticized before, with naysayers asserting that they are simply minerals that appear like biological specimens.
Thanks to advances in technology to further analyze the rock in question more closely, the new research has now brought things to a close.
"I think it's settled," Valley says.
This study is published in the journal Proceedings of the National Academy of Sciences or PNAS.