AP BIOLOGY

Detailed explanation-1: -Some characteristics that have distinguished hominins from other primates, living and extinct, are their erect posture, bipedal locomotion, larger brains, and behavioral characteristics such as specialized tool use and, in some cases, communication through language.

Detailed explanation-2: -Walking upright on two legs is the trait that defines the hominid lineage: Bipedalism separated the first hominids from the rest of the four-legged apes.

Detailed explanation-3: -Whereas Old World monkeys have bilophodont molars, hominoids have Y-5 molars, which feature five cusps separated by a “Y”-shaped groove pattern (Figure 5.31).

Detailed explanation-4: -The two main characteristics of hominids are bipedalism and big brains. The brain case, or the skull, has increased in size over time to allow for the enlargement of the brain.