Canadian Sedimentary Rocks Hold Oldest Evidence Of Life On Earth


Scientists claim to have found what could possibly be the oldest evidence of life on Earth in 3.95-billion-year-old rocks found in a northern Labrador region in Canada.

Graphite In 3.95-Billion-Year-Old Rocks

In a study published in the journal Nature on Wednesday, Sept. 27, Tsuyoshi Komiya, from the University of Tokyo, and colleagues reported that they found graphite, a form of pure carbon in the sedimentary rocks.

Geological analysis of the graphite hinted that the material was biologically produced, which could mean that the Labrador graphite would be 150 million years older than the graphites believed to hold the oldest traces of life on Earth. Before the discovery in Canada, the oldest evidence of life was found in 3.8-billion-year-old rocks in Greenland.

"We concluded that the large fractionation between the δ13Ccarb and δ13Corg values, up to 25‰, indicates the oldest evidence of organisms greater than 3.95 Ga," the researchers wrote in their study. "The discovery of the biogenic graphite enables geochemical study of the biogenic materials themselves, and will provide insight into early life not only on Earth but also on other planets."

Graphite May Not Have Been Inorganically Produced

Some scientists, though, are skeptical about the biological origins of the carbon and suspect that the graphite may have been inorganically produced. Matthew Dodd, from the University College London, pointed out that the chemical signature that Komiya and colleagues detected may have been produced by different chemical processes that do not require biology.

"The study is somewhat limited in evidence for biogenecity of the graphite," Dodd said. "The authors rely solely on the isotopic composition of carbon in the graphite, therefore it will take further analyses to provide conclusive evidence."

Implications Of The Discovery

Nonetheless, if the researchers' conclusion turns out correct and the graphite indeed has biological origins, the discovery means that it did not take long before life emerged on our planet. It suggests that life emerged just 500 million years or so after Earth formed. It also means that early life on Earth emerged, took root, and survived in a hostile environment.

During the Eoarchaean Era, 500 million years after our planet formed, Earth was littered with volcanoes. The young crust was also too hot to support tectonic activity, and the atmosphere contains ammonia and methane without free-floating oxygen. Asteroids and comets likewise hit the surface, and the sun's brightness was only 75 percent of what it is today.

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