Genes that make you clever may also be cause of autism

THE same genes that cause higher intelligence can also trigger autism, research suggests.

A study of more than 5,000 people found that the genes which are linked with exceptional brain power were also associated with the disorder.

The Yale University authors said that the findings may explain why autism has not been eliminated by natural selection. Genes that have a negative effect on reproductive success normally die out.

The researchers said a variety of genes known to have effects including boosting brain growth were beneficial in most cases, and that is why they continue to be passed on. But the downside is that the same genes increase the chances of autism.

Autism – more properly known as autism spectrum disorders (ASD) – includes Asperger’s disease.

It has long been known that some people with autism have superior abilities in areas such as mathematics and science. It affects four to five times as many males as females. Those with the condition can also have difficulties with understanding language and the rules of social interaction, as well as understanding emotion.

The researchers used a computer model that simulated the effects of natural selection on different sets of genes.

They concluded that the genetic variants found in people with autistic disorder were present at a much higher rate than would be expected by chance. This showed that the genes have a ‘signature for positive selection’.

The authors, writing in PLOS Genetics, said previous research had found many overlaps between autism and having a high IQ. But this was the first time that it had been shown that the genes linked to higher IQ and autism are being positively selected in evolution.