Scientists have discovered what could be the earliest signs of movement on Earth.
They found string-shaped mucus strands left by a slug-like creature crawling through mud 2.1 billion years ago in West Africa.
The strands , found embedded in rock dug up in Gabon, trounces the record for the oldest evidence of motion on Earth.
Previous evidence dated back to 570 million years ago, but the new discovery pushes this back by 1.5 billion years. The results were published in the journal PNAS.
Scientists at The French National Center for Scientific Research (CNRS) used state of the art x-ray tech to examine the ancient rock without breaking into it.
They showed that the ancient mucus strands are up to 6mm across and extend 17 centimeters through the rock.
They were left by a collection of single-celled organisms that bunched together to form a single, slug-like creature, scientists believe.
Tiny creatures that exist today called amoeba do this when resources are scarce.
The ancient slug would have moved every now and then to find new food sources in its wet, muddy habitat.
At the time, Earth was largely covered by calm, shallow oceans – with little land in sight.