Growing Up Fast, Maturing Slowly

The developmental mechanisms that set up brain and body plans are highly conserved across vertebrates. This chapter explores the effects of brain volume increase in hominins on brain organization, and identifies those evolutionary changes to the hominin brain that cannot be explained by size increase alone. Approaching this issue from an evo-devo perspective, it explores the evolutionary changes of prenatal and postnatal brain development that are responsible for increased adult brain size in hominins, and how they affect life history and internal brain organization. The chapter also considers the evolutionary trajectories of brain size, brain organization, and brain shape, and the interaction of these three variables. As brains do not fossilize, the chapter discusses brain evolution based on “endocasts”, that is, imprints of the brain and its surrounding structures in the fossilized internal brain-case.