Roll over, Coelacanth! You are no longer the world’s oldest living fossil, but a mere youngster, believed extinct 80 million years ago until discovered alive in 1938. Actually you weren’t the oldest such Lazarus taxon: that honour used to go to the Monoplacophora class of molluscs, thought to be extinct for 380 million years until discovered alive in 1952. But now an animal has been discovered which makes both of these seem young.
As the BBC reports, scientists have found an explanation for strange tracks made in rocks dated up to 1.8 billion years old. The old theory was that these tracks were made by primitive worms, but there was a problem in that this was more than a billion years before the first worms, or multi-celled creatures of any kind, appeared. The solution has now come to light on the sea bed near the Bahamas; I guess someone was enjoying the idyllic diving conditions when they spotted tracks just like the ancient ones. And they then discovered what was making them: “A single-celled ball about the size of a grape” which crawls slowly through the sea bed mud. Similar “globular or bulbous collapsible bodies” were found fossilised in the ancient rocks.
So here we have a creature which seems to have been crawling about the sea bed unnoticed, covered in mud, and little changed for billions of years, while above them continents have risen and fallen and the seas and the land have been ruled by a succession of different kinds of creatures which haven’t even noticed them. These little balls of jelly seem to be the ultimate survivors.
But even this unnamed creature is young compared to the blue-green algae which form stromatolites. The age given for the oldest stromatolites known to have been formed by living creatures is 2.7 billion years, and they are still being formed in the same way. In that ancient period stromatolites were common, but now they are very rare, and indeed one of the few places where they survive today is the sea bed near the Bahamas.