ADDIS ABEBA — Scientists have discovered a nearly complete cranium of an early human ancestor, estimated to about 1.5 million years ago, and a partial cranium dated to about 1.26 million years ago, from the Gona study area in Ethiopia’s Afar region.
Both crania, assigned to Homo erectus, were associated with simple Oldowan-type and more complex Acheulian stone tool assemblages.
This suggests that H. erectus had a degree of cultural/behavioral plasticity that has yet to be fully understood.
The team was led by Sileshi Semaw of the Centro Nacional de Investigación sobre la Evolución Humana (CENIEH) in Spain and Michael Rogers of Southern Connecticut State University. U-M geologist Naomi Levin coordinated the geological work to determine the age of the fossils and their environmental context.
The team’s findings were published March 4 in the journal Sciences Advances.
Gona is located in the Afar Triangle of Ethiopia, adjacent to the well-known Middle Awash and Hadar study areas, where the famous skeletons “Ardi” and “Lucy” were found, respectively.
The nearly complete cranium was discovered at Dana Aoule North (DAN5), and the partial cranium at Busidima North (BSN12), sites that are 5.7 kilometers apart.
The research team has been investigating the Gona deposits since 1999, and the BSN12 partial cranium was discovered by N. Toth of Indiana University during the first season.
The DAN5 cranium was found a year later by the late Ibrahim Habib, a local Afar colleague, on a camel trail.
The BSN12 partial cranium is robust and large, while the DAN5 cranium is smaller and more gracile, suggesting that H. erectus was probably a sexually dimorphic species.
Remarkably, the DAN5 cranium has the smallest endocranial volume documented for H. erectus in Africa, about 590 cubic centimeters, probably representing a female, according to Southern Connecticut State University.
The smallest Homo erectus cranium in Africa, and the diverse stone tools found at Gona, show that human ancestors were more varied, both physically and behaviorally, than previously known, according to the researchers.
This physical diversity is mirrored by the stone tool technologies exhibited by the artifacts found in association with both crania.
Instead of only finding the expected large handaxes or picks, signature tools of H. erectus, the Gona team found both well-made handaxes and plenty of less-complex Oldowan tools and cores.