Human’s oldest ancestor found in Burgess Shale

Researchers from the University of Toronto, the Royal Ontario Museum (ROM) and the University of Cambridge have confirmed that a 505 million-year-old creature, found only in the Burgess Shale fossil beds in Canada's Yoho National Park, is the most primitive known vertebrate and therefore the ancestor of all descendant vertebrates, including humans. The research team's analysis proves the extinct Pikaia gracilens is the most primitive member of the chordate family, the group of animals that today includes fish, amphibians, birds, reptiles and mammals. Their study is based on the analysis of 114 specimens and is published in the British scientific journal Biological Reviews . Pikaia was first described, on the basis of only a few specimens, by American palaeontologist Charles Doolittle Walcott in 1911 as a possible annelid worm, a group that includes today's leeches and earthworms. However, scientists have long speculated that Pikaia was a chordate because it appeared to have a very primitive notochord - a flexible rod found in the embryos of all chordates - which goes on to make up part of the backbone in vertebrates. "Our analysis provides evidence that Pikaia indeed had a notochord," said co-author of the study Jean-Bernard Caron, an assistant professor of ecology and evolutionary biology at U of'T and curator of invertebrate palaeontology at the ROM. A nerve cord and vascular system were also identified in their study.