Eighth Edition
by Harold L. Levin

Chapter 17 - page 4

Human Origins

Genus Homo

The genus Homo arose nearly 2.5 million years ago when australopithecines evolved into the ancestors of humans, Homo ergaster, also called Homo habilis.

Homo rudolfensis and Homo ergaster/Homo habilis lived in Africa around 2 million years ago.

The evolutionary transition may have been stimulated by the change to a cooler, drier climate about 2.7 million years ago. Rainforests were replaced by grasslands. In this environment, selective pressures may have led to bipedalism, greater intelligence, and the ability to make stone tools. Stone tools are found with fossils of Homo.

Genus Homo has a larger cranial capacity and some smaller teeth, but no striking anatomical differences.

Homo erectus arose from Homo ergaster/Homo habilis.

The opening at the base of the skull, where the spinal cord joins the brain, called the foramen magnum, is in a more forward position in Homo erectus, indicating that it had a more erect posture.

Comparison of replicas of Homo erectus (left) and Lucy, Australopithecus afarensis (right) skulls. Photo courtesy of Pamela Gore.

The Homo erectus Stage

Homo erectus (formerly known as Pithecanthropus erectus from Java and Sinanthropus pekinensis from China) is the first hominid known to have moved from Africa into Eurasia.

Homo erectus fossils include:

1. A 1.8 million years jaw in the Caucasus Mountains of Georgia
2. A 1.5 million years complete skeleton from east Africa near Lake Turkana (long-limbed, tall and slender with a remarkably modern skeleton)
3. A 750,000 year old skull cap from Olduvai Gorge

Homo erectus lived in the Early to Middle Pleistocene.

Homo erectus skull replica. Peking man, also known as Pithecanthropus pekinenses and Sinathropus pekinenses. Reconstructed from the remains of several individuals found in caves in Zhoukoudian/Choukoutien, China. About 400,000-500,000 years old. Photo courtesy of Pamela Gore.

Homo erectus reconstruction, Zhoukoudian/Choukoutien, China, about 400,000 years old. Photo courtesy of Pamela Gore.

A rapid increase in brain size had begun in Homo erectus.

Homo erectus skull characteristics:

1. Cranial capacity was 775 - 1300 cm³, slightly less than (or overlapping the lower range of) that of modern humans
2. Skull was rather massive and flat
3. Heavy, bony supraorbital (brow) ridges
4. Sloping forehead
5. The jaw jutted forward at the toothline, a condition called prognathous
6. The nose was broad and flat
7. The teeth were robust but essentially modern
8. Lacked a jutting chin

Homo erectus was a toolmaker and hunter. It is unclear whether they had language, wore clothes, built dwellings or used fire.

Document created by: Pamela J. W. Gore
Georgia Perimeter College, Clarkston, GA

March 6-7, 2006