KNM-ER 1470 cranium, and the recently discovered lower jaw KNM-ER 60000 (Image: Fred Spoor ) The lower jaw KNM-ER 60000 (Image: Mike Hettwer, courtesy of National Geographic)

Few treasure hunts last 40 years. Fewer still end with the unearthing of three bits of broken bone that could help untangle the roots of our family tree.


In 1972, the skull of an early human – known as KNM-ER 1470 – was found in Koobi Fora in northern Kenya. Homo habilis, an early member of our own genus, was thought to have had the plains of Africa to itself 2 million years ago, but the 1.9-million-year-old skull didn’t quite fit with the known remains of that species.

Some were convinced this was a tantalising glimpse of a whole new species, dubbed Homo rudolfensis. Others attributed the differences in shape between this skull and others belonging to Homo habilis to geographical or sexual variation within the species – the unusually large 1470 skull perhaps belonged to a male H. habilis. Without any other specimens to decide either way, the debate rolled on.

Meave Leakey and her colleagues have now discovered three new fossils that share many of the distinctive features of the anomalous skull. The finds finally look set to confirm that the 1470 skull is not an anomalous oddity, but belonged to a distinct species, which will probably continue to be called Homo rudolfensis.

Given the paucity of previous specimens, the three new fossils – a well-preserved face, a complete lower jaw, and part of a lower jaw – are a rich haul. To find such complete fragments is very unusual, Leakey says.

The new face is smaller than 1470 and belonged to a juvenile, but it has the same long, flat form that has bugged Leakey ever since 1972. “It’s been a long search,” she says.

Unlike the 1470 skull, the new face still has many of its teeth, making it possible to work out the probable shape of the lower jaw – another feature lacking in the 1470 skull. Both of the new jaws are a likely fit for the species.

Together, the finds confirm that the differences between Homo habilis and Homo rudolfensis are too great to imply they are male and female members of the same species. No modern ape shows such an extreme level of difference between male and female members of the species.

The fossil record actually suggests there were three roughly contemporaneous species of Homo around 2 million years ago. “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 says.

However, this still might not tie things up completely. In a commentary piece published alongside the new paper, Bernard Wood at George Washington University in Washington DC notes that some researchers have suggested that our evidence for Homo habilis and Homo rudolfensis stretches the definition of the genus Homo too far. While it now seems certain that these fossils belong to two distinct species, we may yet find that they are not in fact part of the same lineage that led to Homo sapiens.

Journal reference: Nature, DOI: 10.1038/nature11322