Molecular fossil solves paleontology mystery

Abstract

If you could travel back in time some 580 million years, you’d face a stark landscape lacking macroscopic animals or plants. Just 40 million years later, ancestors of many animal lineages existing today sprang to life. But in that intervening stretch 570–540 million years ago, toward the end of the geological Ediacaran period, mysterious creatures populated Earth’s seabeds—and paleontologists have argued for decades about whether these organisms were animals; lichen; giant, single-cell amoeba-like organisms; or some other type of being. By analyzing the sterols present in a fossilized Ediacaran organism called Dickinsonia that was found with some soft tissue preserved, Jochen Brocks, a paleobiogeochemist at Australian National University, says his lab has now settled the debate: The fossil’s high abundance of cholestane—essentially fossil cholesterol—relative to other molecular skeletons pegs it as an animal (Science 2018, DOI: 10.1126/science.aat7228). Brocks’s team discovered the Dickinsonia and other E...