Slowly rolling across the ocean floor, a humble single celled creature is poised to change our understanding of how complex life evolved on earth.

The grape-sized Gromia sphaerica, a distant relative of microscopic amoebas, had previously been discovered lying motionless at the bottom of the Arabian Sea.

The oldest fossils of animal trails, called 'trace fossils', date to around 580 million years ago, and palaeontologists believed they must have been made by multicellular animals with complex, symmetrical bodies.

But G. sphaerica's traces are the spitting image of the old, Precambrian fossils; two small ridges line the outside of the trail, and one thin bump runs down the middle.