ABSTRACT
Encephalization, which represents the additional processing capacity beyond that required for routine control of body functions, accelerated with the evolution of the primates, reflecting their visuomotor adaptations. Further increases in encephalization occurred with the advent of the hominids, presumably reflecting the growth of cognitive maps. Thus embryological neurogenetic processes ultimately determine both target brain size of the adult and ultimate body size. While mammalian brain-body size trends are usually reported in terms of adult values, it may well be instructive to view them as endpoints of ontogenetic brain-body growth trajectories. During embryogenesis, the architecture of the brain is under the control of a host of poorly understood neurochemical factors, and it is then that neurodevelopmental disorders as ultimately devastating as autism and schizophrenia may first strike. Nevertheless, humans are unusual in the prolonged duration of brain growth for up to a year after birth, perhaps as a consequence of full bipedal terrestriality.
