Hominids split from animals that looked like chimpanzees 7 Ma, which is the time of the first fossil with evidence of bipedalism. After. The first homo species with larger brains than chimpanzees lived 2.5 Ma. At this point, brain size steadily increased in size until the appearance of Neanderthals and Homo sapiens in the last several hundred thousand years. There might have been a dramatic transformation of humans in South Africa approximately 100,000 years ago although some anthropologists do not agree.
The shift to bipedalism was one of the most important developments in the evolution of humans. It was a “morphological and behavioral markers of our lineage.” It ultimately led to brain expansion, tool use, language, body hair loss, and other characteristics of humans.
Humans (Homo sapiens sapiens) are classified within the genus Homo (a single genus can have several species). There have been three traditional members of the Homo genus: Homo sapiens, Homo neanderthalensis, and Homo erectus. After the discovery of Homo rudolfensis (2.4–1.9 Ma) and Homo habilis (2.4–1.4 Ma) fossils, these species were added to the Homo genus; however, there is still some controversy over whether these two species should be classified as Homo.
After Homo habilis, the next human ancestors in the fossils record, Homo erectus, appeared approximately 2 Ma and survived until 500 ka years ago. Homo erectus brains (900-1100 cc) were much larger than previous Homo species and they had human-like body proportions. The teeth of Homo erectus are similar to human teeth (no large canines).
Neanderthals, Homo sapiens neanderthensis, appear in the fossil record approximately 300,000 years ago. They lived in cold climates in Europe, the Middle East, and the Steppe. Their bodies were adapted to cold climates and were thus shorter and stockier than Homo sapiens. Although their brains (1200 – 1700 cc) had approximately the same volumes as Homo sapiens (1000 – 1800 cc); their skulls were flatter and longer, and they had distinct eyebrow ridges, as with other archaic humans.
Homo sapiens means "wise man." There were three stages in the evolution and dispersion of modern humans around the world. First, anatomically modern humans evolved from archaic homo erectus ancestors in Africa. Second, modern thinking humans probably first appeared in southern Africa. There is debate over whether the advent of modern thinking was relatively sudden or gradual. Some people think humans underwent a dramatic transformation in South Africa. Subsequently, third, modern thinking humans left Africa and spread around the world. This is called the Out of Africa model of human evolution.
Homo sapiens (us) left Africa approximately 50,000 years ago and populated the entire world over the next 40,000 years. The scientific concept that all humans descended from a people group in Africa is called the Out of Africa model of human origins. Mitochondrial haplotypes document the paths of human migration as if people left behind pieces of paper with their names on them (Figure 13‑23).
Near the end of the sixth age, Moses described a modification of humankind, assuming that the word “make" has its normal meaning: a modification of something that already exists.
Children clapping in Madagascar. Credit: Hery Zo Rakotondramanana . Used here per CC BY-SA 2.0.