Finally, aswe mentioned in the introduction, changes in climatic factors
have been also ascribed as “prime movers” in the evolution of the
brain in hominids. First, the fall in Earth temperature during the last millions
years may have caused a general increase in body size by
prolonged growth, resulting in even greater increases in brain size due
to the strong positive allometry of brain size with body size during
fetal and early postnatal growth (the “proportional growth prolongation”
hypothesis; Vrba, 1994, 1998). Second, the increase in climatic