When did the Earth reach oxygen levels sufficient to support animal life? Researchers from McGill University have discovered that a rise in oxygen levels occurred in step with the evolution and expansion of complex, eukaryotic ecosystems.
When did the Earth reach oxygen levels sufficient to support animal life? Researchers from McGill University have discovered that a rise in oxygen levels occurred in step with the evolution and expansion of complex, eukaryotic ecosystems. Their findings represent the strongest evidence to date that extremely low oxygen levels exerted an important limitation on evolution for billions of years.
“Until now, there was a critical gap in our understanding of environmental drivers in early evolution. The early Earth was marked by low levels of oxygen, till surface oxygen levels rose to be sufficient for animal life. But projections for when this rise occurred varied by over a billion years—possibly even well before animals had evolved,” says Maxwell Lechte, a postdoctoral researcher in the Department of Earth and Planetary Sciences under the supervision of Galen Halverson at McGill University.
Ironstones Provide Insights Into Early Life
To find answers, the researchers examined iron-rich sedimentary rocks from around the world deposited in ancient coastal environments. In analyzing the chemistry of the iron in these rocks, the researchers were able to estimate the amount of oxygen present when the rocks formed, and the impact it would have had on early life like eukaryotic microorganisms—the precursors to modern animals.
Read more at McGill University
Image: Ironstones deposited on the seafloor nearly two billion years ago now occur as rocky outcrops along the lakeshore of Tu Nedhé (Northwest Territories, Canada). (Credit: Devon Cole)
