Scientists Uncovers 2.5 Billion-Year-Old Fossil Bacteria That Proved Existence Of Life Before Oxygen

For some living organisms, breathing might just be overrated. A team of researchers from the University of Cincinnati discovered fossilized evidence of bacterial life on Earth before oxygen, at two different locations in South Africa's Northern Cape Province.

This discovery sheds light on the possibility that some life forms, especially those who thrived in the ancient times, have lived fine without any oxygen. The researchers believe the microbes, which fed off sulfur, are the oldest of their kind ever discovered, hinting at the diverse ecosystems in the Earth's past.

"These are the oldest reported fossil sulfur bacteria to date," Andrew Czaja, UC assistant professor of geology, said in a press release by the University of Cincinnati.

"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," he added.

2.5 Billion-Year-Old Sulfur-Oxidizing Bacteria

In the study, published in the journal Geology of the Geological Society of America, the scientists found the bacteria that can oxidize sulfur. The bacteria, which is similar to single-celled organisms today, can be found in deep waters where the amounts of sulfur are high and there are almost no traces of oxygen.

The bacteria are exceptionally large, spherical-shaped and smooth-walled microscopic creatures. In fact, they are much larger than most bacteria found on Earth today. The researchers reveal samples of the bacteria, which were abundant in the deep waters during the Neoarchean Eon period about 2.8 to 2.5 billion years ago.

"These fossils represent the oldest known organisms that lived in a very dark, deep-water environment," Czaja explained.

"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," he added.

Early Life On Earth

In the past, life is thought to begin on Earth almost 3.5 billion years ago with an atmosphere mainly made up of carbon dioxide, ammonia and methane, Mail Online reports.

However, early life forms related to photosynthesizing cyanobacteria gradually leaked oxygen into the atmosphere, which led to the Great Oxygenation Event (GOE) more than 2.3 billion years ago. It was the period that made life forms emerge on the planet.

The new discovery, however, sheds light on the Earth's past and that some creatures survived even before oxygen existed, mainly because they were not dependent on oxygen or sunlight.

There is an ongoing debate about when sulfur-oxidizing bacteria first existed and how that fits into the evolution of life on Earth.

"But these fossils tell us that sulfur-oxidizing bacteria were there 2.52 billion years ago, and they were doing something remarkable," Czaja said.