Nature rather than nurture governs intelligent behaviour in primates, scientists discover

The vexed question of whether intelligence is inherited from birth or acquired through education seems to have been answered – for chimpanzees at least.

Scientists have found that being a smart primate is down to genes rather than upbringing, suggesting that nature rather than nurture governs intelligent behaviour in our closest living relatives.

Researchers have argued for many decades over the genetic basis of human intelligence – based on IQ tests and studies of identical twins reared apart – but now a study has found that a chimpanzee’s “cognitive ability” is mostly governed by its genes rather than its environmental background.

The findings could be important for the understanding of human intelligence and cognitive abilities because whatever genes are involved in chimp behaviour are likely to have a common origin with those involved with human intellectual abilities, the scientists suggest.

“As is the case in humans, genes matter when it comes to cognitive abilities in chimpanzees. It doesn't mean that they are the only factor determining cognitive abilities, but they cannot be ignored,” said William Hopkins of the Yerkes National Primate Research Centre, who led the study published in the journal Current Biology.

“What specific genes underlie the observed individual differences in cognition is not clear, but pursuing this question may lead to candidate genes that changed in human evolution and allowed for the emergence of some human-specific specializations in cognition,” Dr Hopkins said.

The study involved behavioural tests on 99 captive chimps aged between 9 and 54 years. The performance of each ape was measured on a series of standardised cognitive tests for primates and the researchers concluded that about half of the variation in this ability is down to genetic factors – about the same or a little less than humans – and half down to non-genetic influences.

Chimp intelligence, based on their ability to carry out these experimental tests, was not influenced by their sex or their rearing history, whether for instance they were reared by human caretakers or by chimpanzee mothers, the researchers said.

“We found that some but not all cognitive traits were significantly heritable in chimpanzees,” the researchers said in their scientific paper.

“We further found significant genetic correlations between different dimensions of cognitive functioning, suggesting that the genes that explain the variability of one cognitive trait might also explain that of other cognitive traits,” they said.

“Presumably, these attributes would have conferred advantages to some individuals, perhaps in terms of enhanced foraging skills or increased social skills, leading to increased opportunities for access to food or mating,” they added.

Studying the intelligence of chimpanzees could lead to the discovery of particular intelligence-related genes that arose in the last common ancestor of humans and chimps, which existed about 5 million years ago, Dr Hopkins said.

“It is also intriguing to consider what changes in cortical organization [of the brain] might be associated with individual differences in cognition and whether common genes might explain their common variance,” he said.

Researching chimp intelligence has an added advantage over human studies because their behaviour is not complicated by class, culture, schooling or other socio-economic factors, which can influence how well humans perform at IQ tests, the researchers said.