London: Scientists have confirmed that a two-inch-long, worm-like sea creature is the ancestor of all vertebrate life forms.
This means human beings, as well as fish, amphibians, birds, reptiles and mammals are all descended from this creature.
The creature identified as that earliest-known animal to have the beginnings of a backbone is Pikaia gracilens, which evolved more than 500million years ago.
The discovery by Cambridge University scientists also put an end to a debate about whether Pikaia gracilens is the first member of the chordate family, the Daily Mail reported.
Chordates are distinguished by having a ‘notocord’, a flexible rod supporting the nerve running down their back, which, over millions of years, would become the spine in their more advanced descendants.
On both sides of Pikaia’s notocord in a neat zig-zag pattern are around 100 tiny blocks of muscle tissue – called myomeres – which are thought to have allowed it to propel itself quickly through the water by bending its body from side-to-side.
Pikaia had no eyes or teeth but has a clearly defined head, gills to take in oxygen, and two tiny tentacles which may have had some sensory ability to find chemicals to feed on in the water.
“The discovery of myomeres is the smoking gun that we have long been seeking,” said Cambridge professor Simon Conway, who led the study.
“Now with myomeres, a nerve cord, a notocord and a vascular (blood vessel) system all identified, this study clearly places Pikaia as the planet’s most primitive chordate.
“So, next time we put the family photograph on the mantlepiece, there in the background will be Pikaia,” he sated.
The researchers, whose study is published today in the journal Biological Reviews, analysed 114 specimens found in the Burgess Shale in Canada’s Rocky Mountains, one of the world’s most celebrated fossil fields with specimens dating back 505million years.
They used a range of new imagery techniques such as scanning electron microscopes, to reveal finer details in the Pikaia fossils.
It is not clear why Pikaia began to develop a backbone but it may have needed to escape more quickly from predators.