Israeli researchers have proposed a new theory that it was the need to prey on small animals that drove humans to develop larger brains and become the smartest animal on earth.
The researchers posit that by killing off large animals, an abundant source of much-needed fat, Homo erectus, an ancient human species, was forced to move to chase smaller creatures — and the smaller they were, the more ingenuity it took to catch enough of them to meet dietary needs. This, in turn, selected for bigger and more capable brains in the species.
In a paper published on the peer-reviewed MDPI website, Miki Ben-Dor and Prof. Ran Barkai of Tel Aviv University presented their “unifying” hypothesis that the decline in prey size was the “one driver for many key physiological and cultural phenomena in human prehistory.”
The researchers studied the Pleistocene period, covering the period between about 2.6 million to 11.7 thousand years ago, and assessed that there was a relationship between the reduction in the average weight of African animals and the extinction of megafauna, and human brain development in Homo erectus living in the region.
“At the end of this period, humans had established themselves as a species of unprecedented ecological dominance,” they wrote in the paper. “Most notable among these changes was the directional increase in brain volume in the lineages leading to Homo sapiens.”
That included “the habitual use of fire, periodical change of stone-tool technologies, big-game hunting, resource intensification, food production, and animal and plant domestication.”
They suggested that “as prey size declined, humans adapted to acquire and consume smaller and smaller prey” while also adapting to maintain the balance between their biological needs and the energy those needs required, which was obtained from eating.
Humans can’t get all the calories they need by digesting meat, they need fat too. The smaller the animal, the less fat, and the more efficient early humans needed to be at catching them to survive, which required more thought.
“We can’t eat that much protein,” Ben-Dor explained to Haaretz in a report published Thursday. “We need fat too. Because we needed the fat, we began with the big animals. We wiped out the prime adults who were crucial to the survival of species. Because of our need for fat, we wiped out the animals we depended on. And this required us to keep getting smarter and smarter, and thus we took over the world.”
Another key element of human dominance, language, makes significant demands on the brain but was worth the effort because it enabled cooperation for hunting, Ben-Dor said.
“We just need to follow the money,” Ben-Dor said. “When speaking of evolution, one must follow the energy. Language is energetically costly. Speaking requires devotion of part of the brain, which is costly. Our brain consumes huge amounts of energy. It’s an investment, and language has to produce enough benefit to make it worthwhile.”
“What did language bring us? It had to be more energetically efficient hunting,” he concluded.