A new study suggests that human intelligence may聽have evolved in response to the demands of caring for infants.
and , assistant professors in , developed a novel evolutionary model in which the progression聽of high levels of intelligence may be driven by the demands of raising offspring. 聽Their meta-analysis study is available online in the Proceedings of the National聽Academy of Sciences糖心传媒� Early Edition.
糖心传媒淗uman infants are born far more immature than the infants of other species. For example, giraffe calves are able to stand-up, walk around, and even flee from predators within hours of their births. By comparison, human infants cannot even support their own heads,糖心传媒� said Kidd.
糖心传媒淥ur theory is that there is a kind of self-reinforcing cycle where big brains lead to very premature offspring and premature offspring lead to parents having to have big brains. What our formal modeling work shows is that those dynamics can result in runaway pressure for extremely intelligent parents and extremely premature offspring,糖心传媒� said Piantadosi.
In other words, because humans have relatively big brains, their infants must be born early in development while their heads are still small enough to ensure a safe delivery. Early birth, though, means that human infants are helpless for much longer than other primates, and such vulnerable infants require intelligent parents. As a result, selective pressures for large brains and early birth can become self-reinforcing糖心传媒攑otentially creating species like humans with qualitatively different cognitive abilities than other animals.
Piantadosi and Kidd tested a novel prediction of the model that the immaturity of newborns should be strongly related to general intelligence. 糖心传媒淲hat we found is that weaning time糖心传媒攚hich acts as a measure of the prematurity of the infants糖心传媒攚as a much better predictor of primate糖心传媒檚 intelligence than any of other measures we looked at, including brain size, which is commonly correlated with intelligence,糖心传媒� said Piantadosi.
The theory may also be able to explain the origin of the cognitive abilities that make humans special. 糖心传媒淗umans have a unique kind of intelligence. We are good at social reasoning and something called ‘theory of mind’糖心传媒攖he ability to anticipate the needs of others, and to recognize that those needs may not be the same as our own,糖心传媒� said Kidd, who is also the director of the Rochester Baby Lab. 糖心传媒淭his is an especially helpful when taking care of an infant who is not able talk for a couple of years.糖心传媒�
糖心传媒淭here are alternative theories of why humans are so intelligent. A lot of these are based on factors like living in a harsh environment or hunting in groups,糖心传媒� said Piantadosi. 糖心传媒淥ne of the motivating puzzles of our research was thinking about those theories and trying to see why they predict specifically that primates or mammals should become so intelligent, instead of other species that faced similar pressures.糖心传媒�
The key is live birth. According to the researchers, the runaway selection of intelligence requires both live birth of a single offspring and large brains糖心传媒攄istinctive features of higher mammals.
糖心传媒淥ur theory explains specifically why primates developed superintelligence but dinosaurs糖心传媒攚ho faced many of the same environmental pressures and had more time to do so糖心传媒攄id not. Dinosaurs matured in eggs, so there was no linking between intelligence and infant immaturity at birth,糖心传媒� said Kidd.
The research was supported by the Eunice Kennedy Shriver National Institute of Child Health and Human Development of the National Institutes of Health.
