Internal carotid foramina in selected hominin species: (a) Australopithecus africanus, (b) Homo neanderthalensis (cast) and (c) archaic Homo sapiens. All photographs are the same scale (increments in b and c are 0.5 mm) and thus illustrate the increase in foramen size across hominin evolution.
Allometric relationships derived for the brains of 12 species of hominins: (a) mean endocranial volume (Vbr) plotted against body mass (Mb), where . (b) Mean lumen radius (r) of internal carotid arteries in relation to endocranial volume (Vbr), where . (c) Cerebral blood flow rate (), calculated from the size of the internal carotid foramina, in relation to endocranial volume (Vbr), where . Allometric power regressions (solid curves) with 95% confidence bands (dashed curves) are presented on arithmetic axes, but were calculated on log-transformed data.