This document classifies primates into two main groups - prosimians and anthropoids. Prosimians are tree-dwelling, resemble early primates, and are mostly nocturnal. Anthropoids have opposable thumbs, well-developed collarbones, and rotating shoulder joints. Great apes like gibbons, orangutans and gorillas are classified as anthropoids. Humans are also anthropoids and are distinguished by traits like bipedalism, a cup-shaped pelvis, and the ability to speak.