Life on Earth Older than Previous Estimates; Traces of Oxygen Found in 3 Billion-year-old Rocks

We might have to take a second look at the evolution of life on earth.

A study on ancient soils has shown that oxygen was present on earth about three billion years ago, pushing evolution of oxygen-breathing organisms back in time. The study also supports the idea that life might have evolved on other planets.

The appearance of oxygen changed the way life evolved on Earth. Until, now researchers believed that the Great Oxygenation Event- a dynamic period of oxygen accumulation- occurred about 2.3 billion years back. The latest study argues that this event might have occurred 700 million years earlier than previously believed.

The origin of life on earth is still a matter of debate. What we do know is that cyanobacteria- a class of bacteria that photosynthesize and release oxygen introduced the gas to the atmosphere.

"We've always known that oxygen production by photosynthesis led to the eventual oxygenation of the atmosphere and the evolution of aerobic life," said Sean Crowe, co-lead author of the study and an assistant professor in the Departments of Microbiology and Immunology, and Earth, Ocean and Atmospheric Sciences at UBC.

For the study, researchers looked at levels of chromium and other metals in soil samples obtained from South Africa. The samples for the study were collected from The Nsuze paleosol, an ancient soil sandwiched between volcanic and sedimentary rocks, about 3 billion years old. Researchers also obtained samples from Ijzermyn iron formation to compare the levels of minerals, according to Space Reporter.

The experts looked at levels of chromium isotopes to look for traces of oxygen. Isotopes are variants of a chemical with same number of protons, but different number of neutrons. For example Chromium 53 (with 29 neutrons) is heavier than chromium 52 (with 28 neutrons).

During weathering, heavier chromium 53 gets washed from rocks and is deposited in the sea by rivers. This means that marine samples would have higher levels of heavier chromium than terrestrial samples. In the study too, researchers found that marine sediments had higher levels of heavier metal isotopes, Livescience said.

"This study now suggests that the process began very early in Earth's history, supporting a much greater antiquity for oxygen producing photosynthesis and aerobic life," said Crowe in a news release.

According to the researchers, the study also supports the idea that life could have evolved in other parts of the Universe.

"It's exciting that it took a relatively short time for oxygenic photosynthesis to evolve on Earth," Crowe told Livescience. "It means that it could happen on other planets on Earth, expanding the number of worlds that could've developed oxygenated atmospheres and complex oxygen-breathing life."

The study is published in the journal Nature.