The 82nd Annual Meeting of the American Association of Physical Anthropologists (2013)


Early postnatal brain growth in Homo erectus: Incorporating uncertainties

ZACHARY COFRAN1 and JEREMY DESILVA2.

1School of Humanities and Social Sciences, Nazarbayev University, 2Department of Anthropology, Boston University

Friday 9:00-9:15, Ballroom B Add to calendar

Different studies focusing on the Mojokerto calvaria have variously concluded that Homo erectus brain growth was either similar to chimpanzees, within the human range of variation, or overlapping with both species’ patterns. However, these inferences have relied on comparing subadults with adults, due to the absence of fossil neonates. The purpose of this study is to examine early postnatal brain growth in early H. erectus, utilizing recent estimates of cranial capacity and chronological age for the Mojokerto calvaria, and estimates of H. erectus neonatal brain size. Randomization methods, taking into account the ranges of these estimates, are employed to compare H. erectus brain growth with cross-sectional samples of recent humans and chimpanzees between birth and 1.25 years of age.

In the first 1.25 years of life, brain size increases by a median factor of 2.0 and 2.6 in chimpanzees and humans, respectively, with great overlap between species; H. erectus is intermediate, with a median size increase of 2.3 times (resampled) neonatal values. Median absolute size increase is 206 and 558 cm3, in chimpanzees and humans, respectively. Resampled H. erectus values overlap the upper half of the chimpanzee range and are subsumed entirely within the human range, albeit mostly in the lower half. The ‘intermediate’ rate of H. erectus brain growth would have entailed high energy requirements and great parental investment. We discuss implications for H. erectus social behavior and cognition, and suggest applications of the present analytical techniques to questions of australopithecine brain development.

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