People in developing countries have lower IQs because their bodies divert energy from brainpower to fighting disease, researchers claimed today.In hot nations blighted by deadly infections, the priority is survival and populations have evolved to develop stronger immune systems rather than intelligence, according to the controversial theory.
Some critics warned the study could become an excuse for racism if it was used to suggest that people in the Third World are not as smart as those in cooler, richer climes.
People from developing nations where heat and disease are prevalent have lower IQs because their bodies focus on survival, researchers have found
Others pointed out that the ancient Persians, Greeks and Romans lived in hot climates and still boasted extraordinary civilisations.
U.S. researchers claimed their work could explain why national IQ scores vary around the world and are lower in some warmer countries stricken by diseases such as malaria, tetanus and tuberculosis.
Infection could have as important an impact on intelligence as education, diet and wealth, said researcher Randy Thornhill and a team from the University of New Mexico.
Children under five use most of their energy for brain development and this can be restricted if the body has to fight disease, they wrote in the Proceedings of the Royal Society.
They compared data from worldwide IQ studies with disease maps drawn up by the World Health Organisation and concluded that the higher the level of infectious disease in a country, the lower the average national IQ.
'The effect of infectious disease on IQ is bigger than any other single factor we looked at,' said Chris Eppig, lead author on the paper.
Disease is a major sap on the body's energy, and the brain takes a lot of energy to build. If you don't have enough, you can't do it properly.
'The consequence of this, if we're right, is that the IQ of a nation will be largely unaffected until you can lift the burden of disease.'
Critics of the study argued there are many different kinds of intelligence that Western academic-based IQ tests fail to measure.
Low IQ does not necessarily equate to stupidity or incompetence, they said. People in hot countries have the intellectual skills to survive in very difficult environments.
The research could be abused to rationalise racism, just as the Nazis perverted scientific study in the 1930s, some critics said.
Experts pointed out that children fighting debilitating disease are likely to miss a lot of school, which could be the real reason for a lower IQ score, not compromised brain development.
Professor Richard Lynn of Ulster University said the picture was complex, with low national IQs partly propagating the spread of infectious diseases. HIV had a high infection rate in low-IQ nations, he said, because people did not understand how it was contracted and relied on baseless superstitions to avoid it.
Prof Thornhill’s work drew headlines ten years ago when his book A Natural History of Rape controversially argued sexual coercion emerged as an evolutionary adaptation
