LONDON, Jan 31: A team of British scientists has just announced a precise description of humanity’s earliest known evolutionary ancestor – a discovery which gives a whole new meaning to the phrase “old bag”.
The newly named Saccorhytus Coronarius was a microscopic animal which spent its life “wriggling around” on the ocean floor, according to a new study in the journal Nature.
The 540 million-year-old “exquisite” fossil was unearthed during an excavation in China led by University of Cambridge researchers, who say its discovery means humanity can now trace its roots back a further 30 million years.
The creature is thought to be the most primitively example of category of animal life from which humans and other vertebrates eventually emerged.
Most other early deuterostome groups date from about 510 to 520 million years ago, when they had already begun to diversify into vertebrates, as well sea squirts, as well as animals like starfish, sea urchins and acorn worms.
This level of diversity has up till now made it difficult to work out what an earlier common ancestor might have looked like.
Simon Conway Morris, Professor of Evolutionary Palaeobiology at Cambridge, said: “To the naked eye, the fossils we studied look like tiny black grains, but under the microscope the level of detail is jaw-dropping.
“All deuterostomes had a common ancestor, and we think that is what we are looking at here.”
As team leader on the project which discovered fossil, Professor Conway Morris had the honour of naming it.
He said that, while determined to adhere to tradition by using words of classical origin, he was determined to emphasize the organism’s bag-like qualities.
“Saccus refers to bag or sack, and rhytus is from the Greek and refers to folds or wrinkles,” he said.
The study suggests that creature’s body was symmetrical, which is a characteristic inherited by many of its evolutionary descendants, including humans.
Saccorhytus was also covered with a thin, relatively flexible skin and muscles, leading the researchers to conclude that it moved by contracting its muscles and got around by wriggling.
Researchers said one of the most intriguing features of the ancient creature was an apparent lack of an anus.
Evolutionary scientists are able to estimate when species diverged into other species by looking at the difference in their genetic information, working on the basis that the longer two groups have evolved separately, the greater the biomolecular difference between them.
However, creatures before the stage of Saccorhytus were so small that there are very few discoverable fossils which can be checked against this “molecular clock”.
It means the recent discovery may well retain its position as humanity’s earliest known ancestor for a long time while new technology is developed to uncover even smaller fossils. THE TELEGRAPH