A classic example of natural selection at work is the origin of giraffes’ long necks. The ancestors of modern giraffes were animals similar to deer or antelope, with necks of ordinary length.

Although male and female giraffes have the same body proportions at birth, they are significantly different as they reach sexual maturity. Females have proportionally longer necks and longer ...

An analysis of skull and vertebrae fossils suggests that an early relative of giraffes butted heads to compete for mates, which may reveal why modern giraffes are so throaty. “Discokeryx has extreme ...