Humans related to humble mud worm

It doesn't look like us but we share DNA with the worm

This brainless mud worm is a long-lost relative of human beings, scientists have discovered.

It appears the slug-like creature found living at the bottom of a Swedish lake shares its ancestry with people.

It does not have a brain or even sex organs and scientists are baffled about how the Xenoturbella procreates.

However, researchers at Cambridge University are convinced it shares DNA with humans.

The Xenoturbella was originally thought to be related to bivalve molluscs, such as mussels and oysters.

Dr Max Telford, from Cambridge University, who led the British and Danish team, said: "We found this hard to believe as it looks nothing like a bivalve mollusc.

It is fascinating to think that whatever long-dead animal this simple worm evolved from, so did we Dr Max Telford Cambridge University

"We have now been able to show that, amongst all of the invertebrates that exist, Xenoturbella is one of our very closest relatives.

"It is fascinating to think that whatever long-dead animal this simple worm evolved from, so did we."

The new research, reported in the journal Nature, puts humans and the Xenoturbella - whose Latin name means "strange flatworm" - together in the deuterostomes group of species, which contains the vertebrates, as well as starfish, sea urchins and certain marine worms.

Evolution

"Xenoturbella has joined a pretty exclusive group of species," said Dr Telford.

"Alongside vertebrates such as humans, there are only two other groups within this division. Xenoturbella is a significant addition."

Scientists hope studying the worm will give them a better understanding of vertebrate evolution.

Dr Telford added: "One obvious next step for scientists wishing to pursue this line of research is to study the embryonic development of Xenoturbella.

"The challenge now is to find these embryos, because nobody knows how Xenoturbella mates."