Until recently, it was believed that modern humans’ ancestors, of the species Homo erectus, shared the ancient African plains with Homo habilis. But a recent discovery by paleontologist Meave Leakey suggests that they may have been joined by yet another close relative, dubbed Homo rudolfensis.

Between 2007 and 2009, Paleontologist Mauve Leakey and her team found the facial and jaw bones of three different creatures at Koobi Fora, east of Lake Turkana, Kenya. The jaw fragments are believed to be between 1.78 and 1.95 million years old.

Leakey contends that the bones lend weight to the theory that the disputed KNM-ER 1470 skull —discovered by Meave’s husband, Richard, in 1973— is actually a completely different and new human species. The 1470 skull was believed to be an “anomalous oddity” prior to this latest study.

For the past 40 years, the Leakeys insisted that 1470 is not really just a mutation of Homo erectus, as maintained by other scientists at the time.

“The specimens can be readily divided into a Homo erectus group, and two others: one including 1470 and the new specimens, and the other including everything else,” Leakey said in a report in NewScientist.

Leakey said that the bones were “unusually complete”, even retaining several upper teeth. This made it possible to extrapolate the probable shape of the lower jaw of the new species.

Leakey described the new face to be smaller than the 1470. Although it belonged to a younger individual, it still has the “same long, flat form.”

The new human species is has been dubbed Homo rudolfensis after the former name of Lake Turkana, Lake Rudolf.

However, a Huffington Post report said that the Leakeys’ fossils might be difficult to compare with other Homo species as no specimens have been found nearby that could conclusively differentiate the new fossils from those of Homo habilis. Any difference between Homo habilis and the ‘new species’ might be due to variations between sexes of the same species, the report said.

Leakey told National Geographic, “We’ve never known exactly what it was and how it fitted in with anything else.”

In a CBC report, some scientists are not buying Leakeys’ “new species discovery”, as they believe that the Leakeys lack evidence to prove their claim.

Tim White, an evolutionary biologist from University of California Berkeley said that it’s “(S)imilar to someone looking at the jaw of a female gymnast in the Olympics, the jaw of a male shot-putter, ignoring the faces in the crowd and deciding the shot-putter and gymnast have to be a different species.”

Eric Delson, paleoanthropology professor from New York’s Lehman College believes that, while the Leakeys might be correct in their “new species discovery”, the debate will not be over until they have found the specimens of both sexes from the species.

Meanwhile, George Washington University anthropology professor of Bernard Wood wrote an article also in Nature saying that while the new fossils belong to two distinct species, it is still subject to further studies if they are not part of the same lineage that led to the modern man, Homo sapiens.