As the largest animals on the landscape disappeared, the scientists propose, human brains had to grow to enable the hunting of smaller, swifter prey.
This hypothesis argues that early humans specialized in taking down the largest animals, such as elephants, which would have provided ample fatty meals. When these animals’ numbers declined, humans with bigger brains, who presumably had more brainpower, were better at adapting and capturing smaller prey, which led to better survival for the brainiacs.
The hypothesis also explains why brain size shrank slightly, to about 80 cubic inches (1,300 cubic cm), after farming began: The extra tissue was no longer needed to maximize hunting success.
This new hypothesis bucks a trend in human origins studies. Many scholars in the field now argue that human brains grew in response to a lot of little pressures, rather than one big one. But Tel Aviv University archaeologists Miki Ben-Dor and Ran Barkai argue that one major change in the environment would provide a better explanation.
“We see the decline in prey size as a unifying explanation not only to brain expansion, but to many other transformations in human biology and culture, and we claim it provides a good incentive for these changes,” [said] Barkai.