A definitive cause for autism spectrum disorders (ASD) hasremained elusive, although the best picture so far seems to be one of a mix of genetic and environmental factors. This suggests that any genes involved with the condition by necessity are being passed on from generation to generation. A new study now suggests that these genes are being positively selected for.
The study,published inPLOS Genetics, looked at the prevalence of alleles, or gene variants, commonly associated with an increased risk of ASD. The researchersdiscovered that these variants were found in much larger numbers than would beexpected by chance, and they suggest thatthismay be because they are also linked to other genes implicated in cognitive ability.
The authorswrite that this positive selection between the genes thought to contribute to autism and those that might promote intelligence may explain why autism is such a prevalent condition, especially when it seems like itwould have been selected against during human evolution.
It might be difficult to imagine why the large number of gene variants that together give rise to traits like ASD are retained in human populations why arent they just eliminated by evolution? saysco-author Joel Gelernter, professor of genetics and of neuroscience at Yale University, in astatement. 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.
The authors think that the positive relationship might be down to the fact that many of the gene variants found to be associated with ASD are also involved in molecular functions that affect the creation of new neurons. And so while conditions such as autism may be limiting to those who inherit genes that increase their risk for it, the genes are beneficial for our species as a whole as they may help in intellectual achievement.
The study is interesting as a possible explanation, or at least hint, as to why autism is so prevalent, but it still doesnt fully explain the causes behind the condition. These gene variants are thought to increase a person’srisk, but that means you could still carry them and not show signs of autism, and vice versa. It’sa complicated condition and westill have a long way to go before we have a full explanation for it.