Chapter 10: - Protohumans

Summary

This chapter provides a broad overview of primate diversity and evolution, as well as a relatively detailed accounting of early human evolution. It presents a summary of the major anatomical and behavioral differences between apes and humans and the adaptations involved. Humans diverged from the apes between 6 million and 8 million years ago and we have a reasonably good fossil record by 4 million years ago. We can readily track the major adaptive shifts in human evolution, as we became more bipedal and big brained, depending on stone tools by at least 2.5 million years ago. This chapter emphasizes the similarities between apes and humans, and the fact that, evolutionarily, we are apes. Importantly, although there are clear trends through time in hominins, human evolution is not unilineal, and there were as many as seven species and three genera of human existing across Africa at around 2 million years ago, and 27 human species are now known to have existed over the last 7 million years. We were an adaptively diverse group, and the modern idea of a single species of human is a result of a series of extinctions across the hominin order starting around 1 million years ago.