The order of primates contains animals with forward-facing eyes and very flexible fingers, legs and arms. These things evolved as an adaptation to living in the trees. Primates are able to grasp branches and move from limb to limb. Similarly, the forward-facing eyes give them excellent depth perception, to gauge distances accurately between trees. The 235 species of primates are divided into two subgroups: prosimians and anthropoids. Prosimians, such as lemurs, exhibit lower intelligence and have features - like whiskers - that resemble lower-level animals. Anthropoids, on the other hand, are considered the "higher primates." They are larger than other primates, have flat faces and complex brains. Finally, anthropoids are divided into three subgroups of their own: monkeys, apes and hominids.
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