Ancient human ancestor looked like an eel: study
Published Monday, March 5, 2012 4:43PM EST
New research based on fossils found in Canada suggests our earliest ancestor may have looked less like a monkey and more like a worm.
When fossils found in the Rockies a century ago were re-examined over the last three years, researchers realized an eel-type creature had something in common with humans.
Pikaia gracilens, a worm-like sea creature with a spine and central nervous system, shares some of its genes with humans, according research published in the British scientific journal Biological Reviews.
Pikaia was discovered in 1911 in Yoho National Park in the Rocky Mountains. One hundred years later, researchers in Toronto and the U.K. found the five-centimetre-long creature is the earliest-known vertebrate.
At 505 million years old, Pikaia is the earliest known creature in the chordrate group, which includes all vertebrates. Researchers said it's a distant cousin of humans, but humans may not have evolved directly from the small S-shaped swimmer.
Finding an ancestor is "almost impossible" based only on fossils because the evolutionary links are extinct, study co-author Jean-Bernard Caron said.
Caron, the Royal Ontario Museum's curator of Invertebrate Palaeontology, teamed up with Cambridge University professor Simon Conway Morris to study 114 Pikaia fossils found in B.C. They took three years to study the fossils.
Previously, Caron said, all descriptions of Pikaia had been based on only a few samples.
"If you only have one sample, you only have one view," he said. Combining the 60 samples from the ROM with those from the Smithsonian Museum in Washington let Caron and Morris get a three-dimensional view of Pikaia.
Initially, Pikaia was thought to be an early earthworm, Caron said, but when they looked at all the fossils showing Pikaia in different positions, they found the similarities it shares with humans.
Pikaia had a notochord, an early backbone that is similar to the flexible rod found in all vertebrates. They also found a nerve chord, artery system and muscle tissue, all of which are similar to basic human features, Caron said.
"So, next time we put the family photograph on the mantle-piece, there in the background will be Pikaia," Morris said in a press release.
The new findings have convinced Caron to return to the fossil beds in the Burgess Shale area this summer with a group of ROM researchers to look for more specimens.