Color photo of a paleoanthropologist in a hat holding a fossil Australopithecine skull

Enlarge / Yohannes Haile-Salassie poses in the field with the newly discovered skull. (credit: Photograph courtesy of the Cleveland Museum of Natural History)

A 3.8 million-year-old fossil skull is giving anthropologists their first look at an early Australopithecine, the hominin genus that eventually led to modern humans. The skull belongs to a member of a species called Australopithecus anamensis, which many anthropologists have considered the ancestor of the fossil hominin Lucy and the rest of her species, Australopithecus afarensis. But the find suggests that, as with most of these things, the story may be more complicated.

Meet A. anamensis

A. anamensis lived in Eastern Africa between 3.8 million and 4.2 million years ago. Like Lucy, they would have walked upright, but with a gait that we would probably pick out as a little odd. They probably would have still had upper arms adapted to the physical strains of climbing, especially as young children. At the moment, however, those are just assumptions—albeit very likely ones—based on what we know about other Australopiths. That's because, until now, anthropologists knew A. anamensis only from its teeth and jaws. In fact, skulls are hard to find at all in the fossil record before 3.5 million years ago.

That doesn’t sound like much to go on, but the sizes and shapes of teeth changed noticeably between hominin species, so they’re very handy for identification. In fact, paleoanthropologist Yohannes Haile-Salassie and his colleagues identified their newly found skull as A. anamensis based on the size and shape of its canines, which had certain anatomical features that stood out from A. afarensis and other close relatives.

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