The battle for social supremacy could have led to the evolution of human cognitive abilities.
Credit: Priyan Weerappuli
SYDNEY: Human intelligence may have evolved in the battles for social supremacy fought by our ancestors, U.S. scientists say.
Their research supports the 'Machiavellian intelligence' hypothesis, which suggests that competition at a social level - and the ability to manipulate others for personal gain - is what drove an explosive increase in brain size and cognitive abilities of early Homo sapiens.
Sergey Gavrilets and Aaron Vose, from the University of Tennessee, used a mathematical model to show that "the mechanisms underlying the 'Machiavellian intelligence' hypothesis can indeed result in the evolution of significant cognitive abilities on the time scale of 10 to 20 thousand generations." Their findings are published today in the U.S. journal, Proceeding of the National Academy of Sciences.
The human brain underwent a runaway increase in size from about 350,000 years ago until about 35 thousand years ago. Researchers have long wondered what led to this increase, and what our ancestors used their generously proportioned brains for.
According to one theory, intense social competition led to the emergence of strategies for achieving social success including deception, manipulation and alliance formation. In other words, the kinds of traits you regularly see on daytime television. And just like in the soaps, people who employ these strategies are more likely to find a mate.
Over evolutionary timescales the genes that lead to bigger and better brains - and better social skills - became more widespread throughout the species. Now our brains consume 20 per cent of our energy, despite accounting for only 2 per cent of our body weight.
In their study, Gavrilet and Vose created a population model where genes controlled the capacity of brains to learn useful social strategies. Also known as memes, these strategies gave males who possessed them an edge in the fierce competition for mates.
By running simulations of their model over many thousands of generations, the researchers found that the evolution of intelligence passed through three stages. In the 'dormant' phase, the social strategies were a little too complex for the proto-humans' simple minds and they did not easily spread through the population.
During the next phase, which Gavrilet and Vose dub 'cognitive explosion', the population acquired the cerebral capacity to learn and use new memes, resulting in a dramatic increase in the number of memes employed in the population. This corresponds to the explosion in brain size that occurred in human history.
The final phase actually saw a decrease in cognitive capacity because the costs of maintaining highly developed minds began to outweigh their benefits. For example, having larger brains (thus larger heads) would lead to increased death at childbirth. "As the reproductive advantage of having a large brain decreases, there may be a tendency toward a reduction in cognitive abilities," the researchers said.
In their model all memes were considered to be beneficial, but Gavrilet and Vose point out that some ideas can be harmful. This reduces somewhat the advantage of having high cognitive abilities. After all, the ability to have complex ideas means you can have bad ideas too.
While their research demonstrates the plausibility of the 'Machiavellian intelligence' hypothesis, Gavrilets and Vose stress that their model "should not be applied directly to actual human history and society." However it does demonstrate the plausibility of the theory that could best be summed up as "Blessed are the scheming, for they shall inherit the Earth".
