This brainless mud worm is a long-lost relative of human beings, scientists have discovered.
It doesn't look like us but we share DNA with the worm
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
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.
"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
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.
"Xenoturbella has joined a pretty exclusive group of species," said Dr
"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
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