Figure 1. Allometric analysis of brain size, body size, and gestational length by linear regression.

Brain to body weight ratios for adults (A) and neonates (B) are shown for humans (red), other higher primates (blue), and other mammals (black). The black line shows least squares fits to the 91 mammalian species. Neonatal brain (C) and body size (D) to gestational time ratios are displayed for the same species. The blue line shows least squares fits to 15 higher primate species. Allometric data was acquired by Sacher and Staffeldt (1974) [15].