Table S1.
Percent volume and number of cortical neurons in prefrontal region
| Species | % VGM | % VWM | % OWM | % neurons |
| O. garnettii | 9.2 | 3.7 | 7.6 | 8.3 |
| S. midas | 7.4 | 3.6 | 2.8 | 6.4 |
| A. trivirgatus | 9.2 | 1.9 | 7.4 | 7.8 |
| C. apella | 6.6 | 3.0 | 3.6 | 4.2 |
| M. fascicularis | 7.7 | 4.4 | 6.5 | 6.9 |
| P. cynocephalus | 13.5 | 8.0 | 14.4 | 16.2 |
| M. nemestrina | 7.5 | 4.6 | 6.8 | 7.8 |
| Homo sapiens | 10.0 | 5.5 | 7.2 | 7.8 |
% VGM, percentage of gray matter volume contained in prefrontal region; % VWM, percentage of white matter volume contained in prefrontal region; % OWM, percentage of all other (nonneuronal) cells in the white matter contained in prefrontal region; and % neurons, percentage of all cortical neurons contained in prefrontal region.