A 2-million-year-old flat-faced skull found.

A 2-million-year-old flat-faced skull pulled from the sandstones of east Africa has shored up claims that at least three species of early humans once co-existed in an "evolutionary experiment" that saw an explosive increase in brain size paired with radically different faces, teeth, and jaws.
While the new partial skull and two newly found jawbones look radically different from modern humans, they match an enigmatic, nearly complete skull found 40 years ago that paleoanthropologists have long struggled to fit into the human family tree.

Distinct species

Together, the new finds and the puzzling skull describe a species of early humans clearly distinct from two others known from fossils from the same period, said Meave Leakey, the 70-year-old paleoanthropologist who led the team that discovered the fossils.
The "base of the human lineage was indeed diverse," Leakey said from her longtime home at the Turkana Basin Institute in northern Kenya. Her colleagues made the finds near there.
The new fossil report is bound to stir up more controversy in a field long marked by contention.
In an e-mail message, noted UC Berkeley anthropologist Tim D. White wrote: "We still don't understand Homo habilis because there are still too few fossils," referring to another group of early human fossils from the region discovered in the 1960s. "This is a field that continues to be plagued by practitioners unfamiliar with the degree to which individuals within species can vary."
In 2007, an associate of Leakey's noticed a jawbone sticking out of a block of sandstone in the arid region. After hauling the block to their laboratory, the team whittled away with dental drills and revealed a face, its right cheek and upper jaw intact. The small fossil probably came from an adolescent, Leakey's team reports in this week's issue of the journal Nature.

Partial jawbones

Nearby, the team also found two partial jawbones that match both the new skull and the mystery skull.
All of the fossils date between 1.78-million and 1.95-million-years-old.
At that time, East Africa was a roiling hotbed of human evolution. Other fossil finds show that the long-lived species thought to be our direct ancestor, Homo erectus, thrived in the region, which was undergoing rapid changes in plant cover, rainfall and, in all likelihood, availability of various foods.
Another, more primitive hominid species, called Paranthropus bosei, also lived in the region at the time. Stout-bodied and with giant molars, these creatures more closely resembled the more ape-like creatures known as the Australopitecines and are not thought to be human ancestors. Instead of evolving, they died out.
But the new finds - and the mystery skull - clearly don't belong to any of these groups, said Leakey, who is also a National Geographic explorer-in-residence.