Earth may have been teeming with a complex ecosystem of microorganisms as far back as 3. 4 billion years ago.
Scientists, led by the University of Gottingen in Germany, studied fossils taken from the Buck Reef Chert in the Barberton Greenstone Belt in South Africa.
The region is well known for its ancient sedimentary rock close to the surface. These rocks can give a glimpse into our planet’s past.
In some of these rocks, researchers found chemical signatures that provided an insight into the biodiversity of ancient organisms, adding evidence to the early beginning of life on our planet.
“What I’m reading out of this is that early life was working very much similarly to life today,” Frances Westall, an expert in ancient biology from the French National Centre for Scientific Research, who was not involved in the study, told New Scientist.
Life on Earth more than 3 billion years ago
Scientists think that life on Earth began around 4. 3 billion years ago, but tracking down evidence dating back to that time is a difficult task.
Still, by drilling straight into ancient rock, scientists have found peculiar, carbon-rich layers in several cores taken from around the world.
These layers are widely thought to be fossilized life, frozen in rock billions of years ago.
The oldest accepted rock core containing fossilized life was found in Pilbara, Australia. This is thought to be more than 3. 5 million years old.
Older layers of carbon-rich material have been discovered, but due to their age it is not possible for scientists to be sure if they are fossils, or a non-biological phenomenon.
So, scientists are racing to learn as much about these ancient fossils. They’ve discovered that Earth had life on it more than 3 billion years ago.
“It’s very difficult to see the trend, simply because of a lack of well-preserved rocks,” says Westall.
“Personally, I think life emerged on Earth during the Hadean, probably about 4. 2, 4. 1 billion years [ago],” Westall said referring to a period of time that ended about four billion years ago.
Microbes’ metabolisms, billions of years after they died
The samples from the Barberton Greenstone Belt are among the oldest known fossils of life — dating back to about 3. 42 billion years ago.
Earlier analyses had looked at the shape of the fossilized microbes in the rock, suggesting these were varied and probably lived near water.
The new analysis, published in the peer-reviewed journal Precambrian Research on January 12, pushed the analysis even further by looking at the chemicals that made up the microbes.
Their research showed, as predicted, that there was a large number of bacteria who were “photoautotrophs”, meaning they were able convert sunlight into energy. This is similar to some bacteria today.
But they also found evidence that some microbes were likely already able to use up sulfate and make complex chemicals like methane and acetate.
This reinforces the idea that life was already very complex 3. 4 billion years ago, capable of using up carbon in a variety of ways that we still see today, the scientists said in the study.
“These results highlight the existence of an advanced biological carbon cycle as early as 3. 42 Ga ago,” they said.
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