What exactly pushed—or pulled—H. erectus out of Africa is a matter of fierce debate.
Was it some innate adaptability, such as social learning, curiosity, a taste for meat, or technological acuity? Did the expansion of grasslands or rapid changes in climate send them on their journey? Or was it some combination of these factors?
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H. erectus was not simply following spreading savanna as the climate changed but rather had the capacity to adjust to a variety of environments.
“The course of human evolutionary history has been a ratcheting up of different abilities to occupy a variety of environments,” says paleoanthropologist Rick Potts, the head of the Smithsonian Institution’s Human Origins Program, “of eating a greater variety of foods, of being able to respond cognitively and socially to a wider variety of situations.”
He notes that by around 1.4 to 1.6 million years ago, H. erectus was occupying tropical Southeast Asia and Indonesia. “That also by itself is an indicator that it’s not just one type of habitat that is being followed.”
But Potts believes there was an urgent trigger that spurred adaptations: periods of highly variable climate.
