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| Humans are animals, chordates, and vertebrates. We share certain characteristics, such as a more developed nervous system, with other creatures in these categories. Humans are mammals, which means we rely a great deal on a reproductive strategy of few births and extensive parental care. This reproductive pattern is associated with higher intelligence and a greater capacity for learned behaviors. Other adaptations of mammals include differentiated teeth, a skeletal structure capable of swift movement, and the ability to maintain a constant body temperature. Humans belong to a specific order of mammals known as primates. The primates have certain characteristics, such as skeletal flexibility, grasping hands, and keen eyesight, which evolved in order to meet the demands of life in the trees. Although many primate species no longer live in the trees, they have retained these basic primate characteristics and use them in new ways to adapt to the environment. Most humans no longer use their grasping hands to move about in trees, but use them instead for tool manufacture and use. There is a great deal of biological and behavioral variation among the living primates. The order Primates is composed of the more biologically primitive prosimians and the anthropoids, which consist of monkeys (New World and Old World), apes, and humans. Monkeys are quadrupedal (four-footed) and have a tail. Although New World monkeys are exclusively arboreal, some species of Old World monkeys are arboreal and others are terrestrial. The hominoids (apes and humans) are a group of anthropoids that share certain characteristics, such as the lack of a tail, similar dental features, larger brains, and a shoulder complex suitable for climbing and hanging. Hominoids consist of the "lesser apes" (gibbons) and the "great apes." The great apes consist of an Asian form (orangutan) and three African form (gorilla, chimpanzee, bonobo). The African apes are the most similar to humans. The term hominin is used to describe humans and their extinct relatives that lived after the evolutionary split with the African apes. |