Irish and Indian scientists rewrite Earth history
Irish and Indian scientists have rewritten Earth's history by finding oxygen-producing life forms existed 60 million years earlier than thought.
They believe these life forms are responsible for adding oxygen to our atmosphere.
This laid the foundations for more complex life to evolve.
The research was carried out by geologists at Trinity College Dublin and the Presidency University in Kolkata, India.
It found evidence for chemical weathering of rocks leading to soil formation that occurred in the presence of oxygen.
They estimate this took place at least 3.02 billion years ago.
The soil came from the Singhbhum Craton in eastern India, and was named the 'Keonjhar Paleosol' after the nearest local town.
"It shows we can still make findings of early earth. It re-writes the evolutionary history books of when photosynthesis appears" Quentin Crowley, from the School of Natural Sciences at Trinity, said.
"Our research gives further credence to the notion of early and short-lived atmospheric oxygenation"
Such levels of oxygen could only have been produced by organisms converting light energy and carbon dioxide to O2 and water.
Great oxidation event
The widely accepted model for evolution of the atmosphere states that oxygen levels did not considerably rise until about 2.4 billion years ago.
This 'great oxidation event' enriched the atmosphere and oceans with oxygen, and heralded one of the biggest shifts in evolutionary history.
However, recent work on soil from South Africa suggests that oxygen levels may have begun to increase 2.96 billion years ago.
Prof Crowley's findings therefore moves the goalposts back at least 60 million years.
"This is a very exciting finding, which helps to fill a gap in our knowledge about the evolution of the early Earth," Prof Crowley said.
"This paleosol [soil] from India is telling us that there was a short-lived pulse of atmospheric oxygenation and this occurred considerably earlier than previously envisaged."
"This particular example is the oldest known example of oxidative weathering from a terrestrial environment, occurring about 600 million years before the great oxidation event that laid the foundations for the evolution of complex life."