Fossil Discovery Supports Second Human Ancestor Species

The discovery of skull fossils in Kenya support the existence of a human ancestor first suggested in the 1970s, shedding light on the origins of modern people, scientists said.

The unearthing of three remains with distinctive jaw-lines and teeth in the Koobi Fora region of northern Kenya points to a separate kind of early human, of the genus Homo, on Earth almost 2 million years ago, according to a paper published today by the journal Nature.

The fossils provide evidence that an earlier skull finding from 1972 belongs to a new Homo species, the researchers said. That skull has been used to suggest that Homo habilis, sometimes known as the Handy Man, is also an ancestor for today’s humans, known as Homo sapiens.

The further identification of the newly discovered specimen, distinguished by its large flat face and small incisor teeth, means “human evolution is not the straight line that it once was, from our ancestors to us,” said Fred Spoor, study author and professor of evolutionary anatomy at University College London, on a conference call with journalists. “It looks like we are much more diverse creatures who filled different niches.”

The new kind of early Homo is likely to have co-existed with Homo erectus, which is the first species that archaeologists agree was a member of the human family. Diversity among early human ancestors means that “East Africa was quite a crowded place with multiple species,” Spoor said.

Different Face

The variation between the new fossils and existing Homo remains means scientists now have a good idea of what the second ancestral human species looked like, Spoor said.

“The face is very different, reflecting a different mechanical function,” said Meave Leakey, one of the paper’s authors and a paleontologist at the Turkana Basin Institute in Nairobi, Kenya. “We now have two specimens with very distinctive profiles, which are not down to regular variation.”

The fossils show the most complete lower jaw of early Homo ever found according to the paleontologists, who used digital technology to match the discovery with the earlier skull, which was unearthed by Leakey’s husband, Richard Leakey, in Kenya 40 years ago. Mary and Louis Leakey, Richard’s parents, discovered a 1.75 million-year-old skull which first showed the antiquity of hominids in Africa. Their granddaughter Louise Leakey is also a paleontologist based at Lake Turkana with the TBI.

Even after the new findings, the relationship between the 1972 fossil and human origins remains unclear, said Chris Stringer, researcher at the Natural History Museum in London.

“Despite its large brain and its possible use of tools, does it really represent an ancestor for later human species, or do other fossils represent our real ancestor?” Stringer said in a statement.

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