By Maina Kiarie
In 2005 a team of Kenyan and Japanese researchers digging on mud flow deposits in the Nakali region of northern Kenya’s Rift Valley province unearthed a fossil jawbone and eleven isolated teeth. They named it Nakalipithecus nakayamai and dated to 10 million years ago. The genus Nakalipithecus (Nakali ape) is derived from the name Nakali (where it was found) and ‘pithecus’ (ape). Nakayamai is derived from the name of the Japanese geologist Katsuhiro Nakayama who died while working on the project.
According to Kyoto University researchers, Nakalipithecus is very close to the last common ancestors of gorillas, chimpanzees, and humans. Nakalipithecus also resembles Ouranopithecus, another prehistoric hominid species found in Greece.
Nakalipithecus is important in the story of human evolution because together with Ouranopithecus, it provides evidence that the Homininae lineages of today diverged no earlier than about 8 million years ago. Nakalipithecus also supports the theory that the closest relatives of humans evolved in Africa. Some scientists think that modern type great apes went extinct in Africa and that the Homininae were originally an Asian lineage, which later recolonised Africa. This idea is challenged by Nakalipithecus because it is a basal hominin (common ancestor or close to common ancestor).
Until recently molecular studies suggested that the divergence between humans and chimpanzees occurred between 7 and 5 million years ago and that of the divergence of gorillas occurred between 9 and 8 million years ago. The split between gorillas and humans is now thought to have happened as long ago as 10.5 million years ago. The new date was proposed after the discovery of Chororapithecus abyssinucus.
The jaw fossil is about the same size as that of a female gorilla. Nakalipithecus would have been slightly larger than a baboon.