Scientists conventionally divide the causes of human variation into what two categories?

One of the most striking differences between humans and other social mammals is that humans can cooperate in __________ groups of __________ individuals.

Which of the following statements is true of sexual selection?

How do children acquire most of the knowledge they need to survive?

What is the ultimate source of all new genetic variation?

Reciprocal altruism requires

The figure below compares Neanderthal skulls (orange box) with modern human skulls (blue box). What differences do you see?

Sympatric speciation occurs when two populations

There is no increased risk of choking when babies sleep on their backs.

Babies of mothers who smoked during pregnancy are at a higher risk of SIDS.