Brain ontogeny and life history in Homo erectus

Abstract

Coqueugniot et al.’s (2004) recent study of the Mojokerto fossil (Perning 1), an important juvenile Homo erectus specimen from Indonesia, provides valuable insights into the evolution of human ontogeny, life history, and cognition. These authors used computed tomography to study the subarcuate fossa and the bregmatic region in Mojokerto, modern humans, and chimpanzees (Pan troglodytes). These analyses enabled assessment of the age at death and endocranial volume (EV) in the fossil, which suggested that the Mojokerto juvenile died at about one year of age (range: 0.5e1.5 years, and possibly younger) and had an endocranial volume of about 663 cc. Coqueugniot et al. used these estimates to investigate agerelated changes in proportional endocranial volume in H. erectus. Specifically, they calculated proportional EVs by dividing each juvenile’s EV by average adult EV within each species. Mojokerto’s proportional EV was measured at 72e84% of adult volume, indicating that the fossil fell into the range for one-year-old chimpanzees, but possibly above the range for comparably aged Homo sapiens. Based on these results, Coqueugniot et al. proposed that, like some primates, H. erectus gave birth to offspring with proportionately large brains. The authors argued that this result suggests restricted postnatal brain growth in H. erectus, and possibly the absence of secondary altriciality. They also suggested that H. erectus brains matured soon after birth, constraining the development of language and cognitive skills. Despite the high quality and innovative design of Coqueugniot et al.’s study, their analyses leave several important