The Courier & Advertiser (Perth and Perthshire Edition)
Scientists find ‘oldest ancestor’
Microfossil discovery could be common link to many species
Humankind evolved from a bag-like sea creature which had a large mouth, apparently had no anus and moved by wriggling, scientists have said.
The microscopic species is the earliest known prehistoric ancestor of humanity and lived 540 million years ago, a study published in the journal Nature said.
The creature is named Saccorhytus, after the sack-like features created by its elliptical body and large mouth.
Its existence was identified from microfossils found in China.
Researchers believe it was about a millimetre in size, lived between grains of sand on the sea bed and had a large mouth relative to the rest of its body.
It is thought the creature was covered with a thin, relatively flexible skin, had a muscle system which could have made contractile movements, and researchers believe it got around by wriggling.
The study found the creature probably ate by engulfing food particles, or even other creatures, but scientists were unable to find any evidence the animal had an anus.
Simon Conway Morris, of Cambridge University, said: “If that was the case, then any waste material would simply have been taken out back through the mouth, which from our perspective sounds rather unappealing.”
The creature is thought to be the most primitive example of a ‘deuterostome’, a broad biological category that encompasses a number of sub-groups, including the vertebrates.
If the conclusions of the study are correct, Saccorhytus was the common ancestor of a huge range of species, and the earliest step yet discovered on the evolutionary path that led to humans, hundreds of millions of years later.
“All deuterostomes had a common ancestor, and we think that is what we are looking at here,” added Mr Conway Morris.
The study was carried out by an international team of academics, including researchers from Cambridge University and Northwest University in Xi’an, China.
Most other early deuterostome groups are from 510 to 520 million years ago, when they had already begun to diversify into vertebrates, sea squirts, echinoderms – animals such as starfish and sea urchins – and hemichordates – a group including things like acorn worms.