Scientists have discovered the earliest signs of motion on Earth.
They found string lines serving for mucus, left from a dense creature creeping through mud before 2.1 billion years in West Africa.
The guidelines found in a rock dug in Gabon raise the record of the oldest evidence of movement on Earth.
Earlier evidence dates back 570 million years, but the new discovery pushes it for 1.5 billion years. The results are published in the PNAS journal.
Scientists from the French National Center for Research (CNRS) use the latest X-ray techniques to explore the ancient rock without penetrating it.
They showed that the ancient mucus lines are up to 6 mm in diameter and extend to 17 cm across the rock.
They were left from a collection of unicellular organisms that clustered to form a single, snail-like creature, scientists said.
The small beings that exist today call this amoeba when resources are scarce.
An ancient snail would have to move from time to time to find new sources of food for damp and damp habitats.
At that time, the Earth was largely covered by serene, shallow oceans – with little land in sight.