Fetal and infant head circumference sexual dimorphism in primates

Tracey H. Joffe, Alice F Tarantal, Karen Rice, Michelle Leland, Ann Kathrin Oerke, Charles Rodeck, Michael Geary, Peter Hindmarsh, Jonathan C K Wells, Leslie C. Aiello

Research output: Contribution to journalArticlepeer-review

18 Scopus citations


Studies have shown that after controlling for the effects of body size on brain size, the brains of adult humans, rhesus monkeys, and chimpanzees differ in relative size, where males have a greater volume of cerebral tissue than females. We assess whether head circumference sexual dimorphism is present during early development by evaluating sex differences in relative head circumference in living fetuses and infants within the first year of life. Head circumference is used as a proxy for brain size in the fetus and infant. Femur length is used as a proxy for body length in the fetus. Ultrasonography was used to obtain fetal measures, and anthropometry was used to obtain postnatal measures in humans, rhesus monkeys, baboons, and common marmosets. We show that statistically significant but low levels of head circumference sexual dimorphism are present in humans, rhesus monkeys, and baboons in early life. On average, males have head circumferences about 2% larger than females of comparable femur/body length in humans, rhesus monkeys, and baboons. No evidence for head circumference sexual dimorphism in the common marmoset was found. Dimorphism was present across all body size ranges. We suggest that head circumference sexual dimorphism emerges largely postnatally and increases throughout maturation, particularly in humans who reach adult dimorphism values greater than the monkeys. We suggest that brain dimorphism is not likely to impose an additional energetic burden to the gestating or lactating mother. Finally, some of the problems with ascribing functional significance to brain size sexual dimorphism are discussed, and the energetic implications for brain size sexual dimorphism in infancy are assessed.

Original languageEnglish (US)
Pages (from-to)97-110
Number of pages14
JournalAmerican Journal of Physical Anthropology
Issue number1
StatePublished - Jan 2005


  • Baboon
  • Encephalization
  • Human
  • Marmoset
  • Rhesus monkey

ASJC Scopus subject areas

  • Agricultural and Biological Sciences (miscellaneous)
  • Anthropology


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