Data frommodern humans onmean cranial capacity (1350 cm3) and
energetic cost of the brain (14.6W)were taken fromAiello andWheeler
(1995) and used to estimate the volume-specific cost of brain maintenance
(0.0108 W/cm3). Then, we combine this information with data
on cranial capacity for hominid fossils, taken from Shultz et al. (2012),
in order to estimate the energetic cost of brain maintenance for the latter
(Online Table 1). Given the scarcity of data on brain mass-specific
cost for primates, we assumed that no changes in this variable occurred
through hominid evolution. In this sense, data for rhesus monkeys
(Macaca mulatta) and modern humans indicate that mass-specific cost
of brain maintenance is fairly similar in both species (0.037 and
0.033 ml O2 g−1 min−1, respectively; Parker, 1990).