Recent fossil and archaeological finds have complicated our interpretation of the origin and early evolution of genus Homo. Using an integrated data set from the fossil record and contemporary human and nonhuman primate biology, we provide a fresh perspective on three important shifts in human evolutionary history: (1) the emergence of Homo, (2) the transition between non-erectus early Homo and Homo erectus, and (3) the appearance of regional variation in H. erectus. The shift from Australopithecus to Homo was marked by body and brain size increases, a dietary shift, and an increase in total daily energy expenditure. These shifts became more pronounced in H. erectus, but the transformation was not as radical as previously envisioned. Many aspects of the human life history package, including reduced dimorphism, likely occured later in evolution. The extant data suggest that the origin and evolution of Homo was characterized by a positive feedback loop that drove life history evolution. Critical to this process were probably cooperative breeding and changes in diet, body composition, and extrinsic mortality risk. Multisystem evaluations of the behavior, physiology, and anatomy of extant groups explicitly designed to be closely proxied in the fossil record provide explicit hypotheses to be tested on future fossil finds.
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