A 3.8 million-year-old skull belonging to our oldest-known ancestor has been discovered in Ethiopia. The fossil belongs to an ancient hominin (human or human ancestor) with the scientific name Australopithecus anamensis. It is believed to be the direct ancestor of 3.2 million-year-old Australopithecus afarensis, popularly known as “Lucy”. Anamensis dates back to a time when our ancestors were emerging from the trees to walk on two legs, although it still had distinctly ape-like features.

Anamensis is the oldest-known member of the Australopithecus group. Until now, only a handful of teeth, some limb bones and a few fragments of skull belonging to Anamensis had been discovered. The latest specimen, a remarkably complete adult male skull, provides scientists with “the first glimpse of the face of Australopithecus anamensis”, according to paleoanthropologist Yohannes Haile-Selassie of the Cleveland Museum of Natural History, who led the research team.

The skull, slightly larger than a modern adult human’s fist, shows that the fossil, named “MRD”, had a small brain: about a quarter of the size of a modern human's. Although MRD was still ape-like, its canine teeth are smaller than those seen in earlier fossils. There are prominent cheekbones, showing that it could chew tough food during dry seasons when less vegetation was available. A number of features differ from those of Lucy. For example, Amanensis possessed a sloping face, unlike the flat face that Lucy has.

The dating of the skull also reveals that Anamensis and its descendant, Lucy, co-existed for a period of at least 100,000 years. This means that Anamensis, which lived from 4.2 million to 3.8 million years ago, continued to live on after the Lucy group (which lived 3.9–3 million years ago) branched off. The two species—probably separated by geography to begin with—may have later crossed paths and competed for food and territory.