Chimpanzee’s highly heritable intelligence window on human IQ

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A story about chimpanzee intelligence — especially the genetics of chimpanzee intelligence — is really a story about human intelligence. After all, we share some 96 percent of our genetic material, and the similarities between chimps and humans are stunning.

They have language, use tools, even develop distinct cultures. These are all things that, until relatively recently, we thought were uniquely human activities.

So a study in Current Biology from Georgia State University and the Yerkes National Primate Research Center that declares general intelligence in chimpanzees roughly 50 percent heritable (i.e. genetically determined) is a strengthening of the well-established genetic basis for intelligence in humans.

This is the first thorough look at the genetic underpinnings of intelligence in our close kin the primates. The authors of the paper write: “[A]side from early attempts to selectively breed for learning skills in rodents, studies examining the role that genetic factors might play in individual variation in cognitive abilities in nonhuman animals, particularly nonhuman primates, are scare.”

To make up for this scarcity, the authors — led by primatologist William D. Hopkins — put nearly a hundred chimpanzees through a battery of tests. New Scientist’s Andy Coghlan outlines the experimental process:

To assess heritability, Hopkins and his colleagues studied 99 captive chimpanzees – 29 males and 70 females – aged from 9 to 54. The team had the chimps do 13 standard tasks to measure their cognitive abilities.

Hopkins teased out ability in four broad categories: spatial memory and ability; tool use; communication skills; and establishing causality. Tests to remember which of three beakers hid food, for example, helped measure spatial memory, while challenging chimps to obtain visible but otherwise inaccessible food by attracting attention from humans helped measure communication skills.

They also re-tested the same chimps after a year, to see if their data held steady over time. It did. They took all of these tests and combined them to create a “g”-value for each individual, called “g” for general intelligence. This g-value is what they used for broad comparisons, and when they looked for the effects of things like sex (male/female) or rearing history (chimp-reared/human-reared) they found none.

“As is the case in humans,” Hopkins told Science 2.0, “genes matter when it comes to cognitive abilities in chimpanzees. It doesn’t mean that they are the only factor […] but they cannot be ignored.”

Furthermore, the results were “bang on with human results […] showing that results in nearly all of the tests are significantly heritable,” human intelligence genetics researcher Robert Plomin of King’s College London told Coghlan at New Scientist.

This all reinforces the perspective of io9’s Jason G. Goldman, who explains how chimpanzees offer a sort of ‘stripped-down’ version of human intelligence that makes the fundamentals easier to study:

It’s hard to study intelligence in humans — our cultures are incredibly complex, and what counts as “smart” is defined as much by our societies as it is by our genes. So some researchers have turned to chimpanzees to understand what actually gives rise to intelligence in the brain.

Chimpanzee intelligence may be complex, but it’s still not quite the socio-cultural mess that human intelligence often is. So it is their minds and the genes that help build them that may offer the clearest window into our own intelligence yet.

Kenrick Vezina is Gene-ius editor for the Genetic Literacy Project and a freelance science writer, educator, and naturalist based in the Greater Boston area.

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