IV.

Behavior

The physiological adaptations that made humans more flexible than other primates allowed for the development of a wide range of abilities and an unparalleled versatility in behavior. The brain's great size, complexity, and slow maturation, with neural connections being added through at least the first 12 years of life, meant that learned behavior could largely modify stereotyped, instinctive responses. New environmental demands could be met by rapid adjustments rather than by slow genetic selection; thus, survival in a wide range of habitats and under extreme conditions eventually became possible without further species differentiation. Each new infant, however, with relatively few innate traits yet with a vast number of potential behaviors, must be taught to achieve its biological potential as a human.