Alleles in genes linked to autism may have been conserved throughout human evolution because they are also associated with increased cognitive ability, the Independent reports.
Yale University researchers searched for signals of selection around genes associated with neuropsychiatric disorders like autism, but also with attention deficit hyperactivity disorder, bipolar disorder, major depressive disorder, and schizophrenia. As they reported recently in PLOS Genetics, the researchers found that common autism risk alleles were enriched for signatures of incomplete selection. The genes these alleles map to also tend to be expressed in the brain, involved in nervous system development, as well as linked to increased cognitive ability.
"We found a strong positive signal that, along with autism spectrum disorder, these variants are also associated with intellectual achievement," study author Renato Polimanti from Yale tells the Independent.
His coauthor Joel Gelernter, also at Yale, says that these autism-linked alleles haven't gone by the wayside because they offered an advantage. "The idea is that during evolution these variants that have positive effects on cognitive function were selected, but at a cost — in this case an increased risk of autism spectrum disorders," he adds.