The "exquisitely preserved" fossils found in Gabon suggest organisms began moving 2.1 billion years ago. They may, as creatures, have resembled colonial amoeba or slime moulds.
Scientists at the French University of Poitiers report they have discovered the earliest traces of life forms that were able to move independently.
Geologist Abderrazak El Albani and his team's report in the Proceedings of National Academy of Sciences journal asked: "Was this biological innovation the prelude to more perfected forms of movement or an experiment cut short by the drastic drop in atmospheric oxygen rates which occurred approximately 2.083 billion years ago?"
The previous, earliest evidence of moving lifeforms was half a billion years old.
"The more or less sinuous structures are tubular, of a generally consistent diameter of a few millimetres, and run through fine layers of sedimentary rock," the team reported.
Found in an ancient rock in Africa, the findings indicate comparatively complex organisms could have existed more than 1.5 billion years earlier than previously thought.
El Albani and his team reported finding fossils of multicellular organisms in the same rocks in the Franceville basin in Gabon in 2010. “It’s a unique place in the world, where we have this preservation of the rocks,” he said. Most rocks are of this age have been metamorphosed by extreme heat and pressure.
Over the last eight years, the team have made further field trips and collected more than 500 specimens, including the trace fossils.
The team includes scientists and researchers from France, Canada, Sweden, the USA, UK and Denmark. They reconstructed the fossil traces using non-destructive 3D X-ray imaging technology.
The discovery has raised new questions about the history of life.