16.18 Human Evolution

What is a "cave man"?

What if you were to wake up in the Cenozoic, even in the very recent Cenozoic, but with a group of Neanderthals? They were close relatives, but you might find them to be a bit different from your usual friends.

Human Evolution

Humans evolved during the later Cenozoic. New fossil discoveries alter the details of what we know about the evolution of modern humans, but the major evolutionary path is well understood.

Primate Ancestors

Humans evolved from primates, and apes and humans have a primate common ancestor. About 7 million years ago, chimpanzees (our closest living relatives) and humans shared their last common ancestor.

Hominids

Animals of the genus Ardipithecus, living roughly 4 to 6 million years ago, had brains roughly the size of a female chimp. Although they lived in trees, they were bipedal. Standing on two feet allows an organism to see and also to use its hands and arms for hunting. By the time of Australopithecus afarensis, between 3.9 and 2.9 million years ago, these human ancestors were completely bipedal and their brains were growing rapidly (Figure below).

Homo

The genus Homo appeared about 2.5 million years ago. Humans developed the first stone tools. Homo erectus evolved in Africa about 1.8 million years ago. Fossils of these animals show a much more human-like body structure, which allowed them to travel long distances to hunt. Cultures begin and evolve.

Homo sapiens

Homo sapiens, our species, originated about 200,000 years ago in Africa. Evidence of a spiritual life appears about 32,000 years ago with stone figurines that probably have religious significance (Figure below).

The ice ages allowed humans to migrate. During the ice ages, water was frozen in glaciers and so land bridges such as the Bering Strait allowed humans to walk from the old world to the new world.

DNA evidence suggests that the humans who migrated out of Africa interbred with Neanderthal since these people contain some Neanderthal DNA.

Summary

• Australopithecus afarensis was completely bipedal and had a growing brain.
• Homo erectus evolved 1.8 million years ago and left behind signs of an early culture.
• Our species is Homo sapiens, which evolved 200,000 years ago in Africa and continues to today.

Review

1. What are the characteristics that make humans human?
2. Why did the evolution of bipedalism advance human evolution?
3. How did people get from the old world to the new world?