No relative expansion of the number of prefrontal neurons in primate and human evolution

Proc Natl Acad Sci U S A. 2016 Aug 23;113(34):9617-22. doi: 10.1073/pnas.1610178113. Epub 2016 Aug 8.


Human evolution is widely thought to have involved a particular expansion of prefrontal cortex. This popular notion has recently been challenged, although controversies remain. Here we show that the prefrontal region of both human and nonhuman primates holds about 8% of cortical neurons, with no clear difference across humans and other primates in the distribution of cortical neurons or white matter cells along the anteroposterior axis. Further, we find that the volumes of human prefrontal gray and white matter match the expected volumes for the number of neurons in the gray matter and for the number of other cells in the white matter compared with other primate species. These results indicate that prefrontal cortical expansion in human evolution happened along the same allometric trajectory as for other primate species, without modification of the distribution of neurons across its surface or of the volume of the underlying white matter. We thus propose that the most distinctive feature of the human prefrontal cortex is its absolute number of neurons, not its relative volume.

Keywords: cortical expansion; evolution; number of neurons; prefrontal cortex; primate.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Biological Evolution*
  • Cell Count
  • Female
  • Gray Matter / anatomy & histology
  • Gray Matter / cytology*
  • Gray Matter / physiology
  • Humans
  • Male
  • Microtomy
  • Neurons / cytology*
  • Neurons / physiology
  • Prefrontal Cortex / anatomy & histology
  • Prefrontal Cortex / cytology*
  • Prefrontal Cortex / physiology
  • Primates
  • Species Specificity
  • White Matter / anatomy & histology
  • White Matter / cytology*
  • White Matter / physiology