Girls have been faster learners for six million years, chimpanzee study shows

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The Independent Online

A study of young chimpanzees living in the wild might explain the biological reason why infant girls tend to learn faster than infant boys.

A study of young chimpanzees living in the wild might explain the biological reason why infant girls tend to learn faster than infant boys.

Primatologists have discovered distinct sex differences in the ability of young male and female chimps to acquire new skills "taught" by their mothers.

The scientists believe these gender differences in man's closest living relative could have a common evolutionary root with the differences seen in the speed of intellectual development of infant boys and girls.

Educationalists researching how young children learn complex skills should study the findings and take gender differences into account, said Professor Elizabeth Lonsdorf, head of field conservation at Lincoln Park Zoo in Chicago.

Professor Lonsdorf and her colleagues Lynn Eberly and Anne Pusey of the University of Minnesota believe that the gender differences in learning behaviour seen in young chimps and children could date back to when apes and humans last shared a common ancestor, about six million years ago.

Their four-year study, published in the journal Nature, involved filming 14 young chimps living in the Gombe National Park in Tanzania to observe how they learnt complex skills such as "fishing" for termites using a thin stick as a tool.

It has already been established that young chimps learn by watching adult females who lick the stick clean of termites each time they pull it from the termite nest.

But the new study has demonstrated there is a distinct difference between how quickly females and males pick up this cultural trait, Professor Lonsdorf said. Even though mothers showed no preference in teaching sons or daughter, it was the daughters who closely copied their mothers while the sons would quickly lose patience and break away to play games.

On average, females learnt to extract termites using a fishing stick at the age of 31 months, whereas it took males 58 months to reach the same standard. The females fished more often and caught more termites each time they dipped a stick into a termite mound.

Professor Lonsdorf also found that each mother fished in a particular way, dipping her stick into the termite nest to a given length. She showed that the daughters learnt how to fish in the same way as their mothers, whereas the sons did not.

"Our findings indicate that female chimpanzees start to fish for termites at a younger age than males; they are more proficient than males once they acquired the skill; and they each use a technique similar to their mother's, although males do not," Professor Lonsdorf said.

"To our knowledge this is the first systematic evidence of a difference between the sexes in the learning or imitation of a tool-use technique in wild chimpanzees," she said.

For chimpanzees, the differences in learning how to use a fishing stick makes sense. Termites are a vital source of dietary protein for females whereas male chimps can hunt for small monkeys. "The availability of animal protein is limited for chimpanzees. Mature males often hunt monkeys in trees, but females are almost always either pregnant or burdened with a clinging infant," Professor Lonsdorf said.

"Termites are a rich source of protein and fat. Females can fish for termites and watch their offspring at the same time," she said.

Adult females spend more time termite fishing than adult males, which means that the young of both sexes seem to pursue activities at a very early age that are related to their different roles in later life, she added.

This may have also been the case with the last common ancestor of apes and humans, and it could account for the gender differences seen in human children today.

"This finding is a heads up to researchers studying the learning of relatively complex skills that they should take sex into account," Professor Lonsdorf said.

"A similar disparity in the ability of young males and females to learn skills has been demonstrated in human children and may be indicative of different learning processes.

"A sex-based learning difference may therefore date back at least to the last common ancestor of chimpanzees and humans," she added.