Two crania from Gona assigned to Homo erectus—the DAN5 skull dated to 1.55 million years ago (Ma) and the BSN12 partial skull dated to 1.26 Ma, earlier published in Science Advances (Semaw et al., 2020)—were reanalyzed, and CENIEH scientists Sileshi Semaw and Emiliano Bruner, and colleagues reported results of their investigations in a recent paper published in the Journal of Human Evolution (https://doi.org/10.1016/j.jhevol.2021.103102; online December, 2021).

A comparative study with a larger sample (n=38) demonstrated that some of the difference in endocranial volume between the two Gona fossils reflects broader species-level brain expansion from 1.77 to 0.1 Ma. The BSN12 partial cranium is markedly larger than the DAN5 skull (598 cubic centimeters), but both fossils represent the smallest adult H. erectus known from their respective time periods in Africa.

Although the DAN5 cranium bears a particularly close affinity to the Georgian H. erectus fossils at Dmanisi and to Kenyan fossils assigned to H. habilis, the study confirmed that the DAN5 fossil is likely early African H. erectus, though the smallest yet found in Africa.

The earlier study attributed the differences in size and robusticity of the two fossils to either sexual dimorphism or anagenetic evolution. The current study concludes that no clear pattern of sexually patterned size or shape differences are shown within H. erectus based on current assessments of sex for individual fossils.