|Homo ergaster/erectus skull|
The genus began about 2.3 million years ago. Their ancestors were almost certainly some line of Australopithecine apes. Species of Homo have:
- A larger brain (above 900ml)
- Improved walking and running ability.
As the process continues, the forehead becomes more vertical, the skull becomes rounder, the teeth are reduced in size, arms are shorter and legs are longer. The skeleton becomes more delicate. particularly in our species.
- Alexander, Richard D. 1990. How did humans evolve? Reflections on the uniquely unique species. Special Publication. Ann Arbor, MI: Museum of Zoology, University of Michigan.
- Flinn, Mark V.; Geary, David C.; Ward, Carol V. 2005. Ecological dominance, social competition, and coalitionary arms races: why humans evolved extraordinary intelligence. Evolution and Human Behavior. 26 (1): 10–46. 
- Hartwig, Walter C., ed. 2002. The Primate fossil record. Cambridge Studies in Biological and Evolutionary Anthropology. 33. ISBN 978-0-521-66315-1