Chapter Summary

The primates are one of the earliest of the existing mammal groups to evolve after the mass extinction of 65 mya. They appear to have evolved first in what are now North America and Europe, but the success of their adaptations allowed them to radiate over the Old World and into the New World.

About 23 mya, the hominoids appear in the form of primitive apes. This successful group has left fossils all over Africa, Europe, and Asia. It is from one of the African apes that our family, Homindae, branched off from some 5 or 6 mya.

The evolution of habitual bipedalism marks the beginnings of our family and was the major distinguishing characteristic of this family for the first half of its time on earth. Bipedalism may have begun as part of one group’s adaptation to the forests. We still see this trait—along with food sharing and sexual consciousness—in today’s bononobos. However, these adaptations would also prove useful in Africa’s increasingly variable environment, and the hominids soon were well established and radiated—perhaps from Ardipithecus—into three distinct groups, often classified as separate genera: Australopithecus, Paranthropus, and Homo.

The first two genera, Australopithecus and Paranthropus, with their chimp-sized brains, remained largely vegetarian and persisted until nearly 1 mya. They eventually lost out to a combination of environmental change and competition from the third hominid genus, Homo, with its bigger brain and ability to manipulate its environment both mentally and technologically, including making the stone tools. These adaptations allowed the earliest members of our genus to more safely and efficiently exploit an abundant and reliable new food source—meat scavenged from natural deaths among the great herds of savanna animals. This adaptive base led, as we will see in the next chapter, to the further radiation of this type of hominid, who eventually became one of the earth’s dominant species.

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