Scientists Discover Evidence of Ancient Life on Earth Before Oxygen Existed

A team of researchers from the University of Cincinnati has discovered proof that early life forms that lived on Earth thrived even without oxygen billions of years ago.

The study, published in the journal Geology of the Geological Society of America, discovered a 2.52-billion-year-old bacteria that can oxidize sulfur. The said bacteria is similar to single-celled organisms in present time that can be found in deepwaters where amounts of sulfur are high. The smooth-walled spherical bacteria is larger in size compared to modern bacteria.

The researchers found ancient rocks which hold fossilized evidence of this bacteria in two locations: one in South Africa and another in the Northern Cape Province. Andrew Czaja from UC, Nicolas Beukes from the University of Johannesburg and Jeffery Osterhout, a UC master's graduate, discovered that during the Neoarchean Eon, which dates back 2.8 to 2.5 billion years ago, these sulfur-oxidizing bacteria thrived in the depths of the ocean.

"These fossils represent the oldest known organisms that lived in a very dark, deep-water environment. These bacteria existed two billion years before plants and trees, which evolved about 450 million years ago. We discovered these microfossils preserved in a layer of hard silica-rich rock called chert located within the Kaapvaal craton of South Africa," Czaja told Science Daily.

The researchers noted that the Neoarchean Eon was a time where the atmosphere only contained one percent oxygen. Because of an extremely different atmospheric makeup, the researchers believe that a set of different creatures that did not need sunlight or oxygen lived in deep waters during that time.

The team used radiometric dating and geochemical isotope analysis to determine that the fossils they found were during the said time. During the Neoarchean Era, before the shifting of tectonic plates, the team said that South Africa and Western Australia belonged to a supercontinent called Vaalbara.

"These are the oldest reported fossil sulfur bacteria to date. And this discovery is helping us reveal a diversity of life and ecosystems that existed just prior to the Great Oxidation Event, a time of major atmospheric evolution," Czaja said.