Chapter 19: Human EvolutionOverview |
The human implications of evolutionary biology have been, and remain, a cause of heated controversy. In 1925, Tennessee school-teacher John T. Scopes was convicted of violating a new state law prohibiting the teaching of evolution. The Scopes case was popularly known as the Monkey Trial, indicating that for many observers the central issue at stake was the origin of the human species. In 1995, the Alabama state board of education ruled that all textbooks discussing evolution must carry a disclaimer admonishing readers to consider evolution as theory, not fact. National Public Radio reporter Debbie Elliot interviewed members of the school board about their decision (National Public Radio 1995). Again, the origin of our species was a key issue. Board member Stephanie Bell, for example, told Elliot, “Most people do not believe that we evolved from apes.”
Refer to Chapter 19 to explore research on the evolutionary history of our species.
19.1 Relationships Among Humans and the Extant Apes Humans (Homo sapiens) belong to the primate taxon Catarrhini (Goodman, et al. 1998), which includes the Old World monkeys, such as the baboons and macaques, and the apes (Figure 19.1). The apes include the gibbons (Hylobates) of Southeast Asia and the great apes. The great apes include the orangutan (Pongo pygmaeus), also of Southeast Asia, and three African species: the gorilla (Gorilla gorilla), the common chimpanzee (Pan troglodytes), and the bonobo, or pygmy chimpanzee (Pan paniscus).
Refer to section 19.1 of your textbook to learn about how we are related to these fascinating creatures.
19.2 The Recent Ancestry of Humans According to the evidence, humans and the two chimpanzees last shared an ancestor about 5.4 million years ago. With appropriate caution, we can use what we know about humans, chimpanzees, and bonobos to infer something of the nature of that last common ancestor. It is probable that we inherited from it at least some of the behaviors that are shared by its three descendants today.
Turn to section 19.2 of your textbook to learn more about our recent ancestors.
19.3 The Origin of the Species Homo sapiens There is considerable uncertainty and debate, however, over how many species they actually represent and how modern humans, Homo sapiens, emerged from among the others.
Turn to section 19.3 of your textbook to explore the research and controversies surrounding the origins of modern humans.
19.4 The Evolution of Uniquely Human Traits Humans have a number of traits that are unique among extant primates: We walk bipedally, we have very large brains, we manufacture and use complex tools, and we use language.
Refer to section 19.4 of your textbook to consider evidence on the origin of tools and language.