The first multicelled life appeared on Earth more than 1.5 billion years earlier than previously thought, new fossil discoveries show.
t had previously beeen believed that until the so-called Cambrian explosion 600 million years ago, the only life on Earth was single-celled microbes, or prokyarotes.
But the new fossil organisms unearthed in Gabon appear to date back three and a half billion years.
More than 250 specimens have been collected so far, and a hundred studied in detail. Some are up to a foot long - too large and too complex to be prokaryotes or eukaryotes. They come in a range of shapes and sizes, showing that different types of life co-existed during the early Proterozoic.
To demonstrate this, researchers at the University of Poitiers relied on several advanced techniques to identify thesamples and reconstruct their environment.
Using an ion microprobe, the researchers were able to distinguish organic remains from the local clay. Through microtomography - a high resolution three-dimensional scan - they were able to reconstruct the samples in 3D and examine their internal structure.
The creatures appear to have lived in colonies, with more than 40 specimens found in a half-meter square. They lived in shallow seas, often gentle but periodically affected by tides, waves and storms.
To develop over 2.1 billion years and achieve such differentiation, the team believes that these life forms may have benefited from a significant but temporary oxygen increase in the atmosphere known to have occurred around the time of the new fossils.
The team plans to continue examining the history of the Gabon basin, looking for more fossils and also examining the mineral content of the surrounding rock to find out more about the levels of oxygen at the time.
The research appears in Nature.