Fossilized remnants of ancient carbon from the heart of South Africa's Mpumalanga province have just yielded the earliest chemical evidence yet of life on Earth.

According to a new analysis using machine learning, fragmentary traces of carbon from the Josefsdal Chert, dating back 3.33 billion years, are the earliest and most confident detection of biotic chemistry found on Earth to date.

In addition, the team's work identified the oldest evidence for photosynthesis to date in rocks 2.52 and 2.3 billion years old, from South Africa and Canada, respectively – pushing back the documented timeline for the process by more than 800 million years.

"Our results show that ancient life leaves behind more than fossils; it leaves chemical 'echoes'," says mineralogist and astrobiologist Robert Hazen of the Carnegie Institution for Science in the US. "Using machine learning, we can now reliably interpret these echoes for the first time."

Time, decay, and geology are not kind to the traces life leaves behind – and the greater the passage of time, the greater the opportunity for degradation.

In addition, the first life to emerge on Earth would have been tiny microbes, scientists believe, whose physical remnants would have been dramatically altered in the billions of years since they first wiggled around in the primordial damp.

That's not to say they left no traces. Based on their physical structure, formations such as stromatolites are interpreted as the remains of microbial mats, vast communities of microbes so numerous that they left behind layers in ancient rock. There is also black chert and shale, as well as carbonate formations, within which ancient, fragmentary traces of fossilized carbon have been retained over eons.

It's difficult to determine with certainty, however, whether these sooty remnants of highly altered carbon were produced by biological or non-biological processes.

Now, a team led by Hazen, in a paper with Carnegie Science astrobiologists Michael Wong and Anirudh Prabhu as first authors, developed a way to positively identify ancient carbon produced by life.