The 81st Annual Meeting of the American Association of Physical Anthropologists (2012)


Mojokerto revisited: assessing brain growth patterns in Homo erectus

CAITLIN A. O'CONNELL and JEREMY M. DESILVA.

Department of Anthropology, Boston University

Saturday All day, Plaza Level Add to calendar

Brain development in Homo erectus is a subject of great interest. Some researchers have suggested that its brain development resembled that of nonhuman apes, while others argue for a more human-like growth pattern. In this study, we retested hypotheses regarding brain ontogeny in H. erectus using new methods (resampling), data from additional H. erectus crania and newly refined endocranial volumes for the Mojokerto calvaria. We assumed that the Mojokerto individual was between 0.5-1.5 years at death, and used brain sizes from similarly aged humans and chimpanzees. Our results reveal a considerable amount of overlap between chimpanzee and human brain development, with humans achieving 65% (±14%) and chimpanzees 81% (±12%) of brain growth by 6 months to 18 months of age. Mojokerto had reached 69%-73% of its adult volume when compared to all H. erectus crania (n=22). When compared to the most relevant specimens from Indonesian sites greater than 1.2 myr (n=9), Mojokerto had reached only 69% of its adult cranial capacity. Mojokerto thus falls within the range of both humans and chimpanzees, though slightly (but not significantly) closer to the average human pattern. These findings do not support the contention that H. erectus had rapid, ape-like brain growth, and have important implications for considering the evolution of human childhood and cognitive abilities. We suggest that Homo erectus would have had a unique developmental pattern that should be considered as an important step along the continuum leading to extreme infant altriciality and long childhood in modern humans.

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