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A definitive cause for autism spectrum disorders (ASD) has remained 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 in PLOS Genetics[open,DOI:10.1371/journal.pgen.1006618][DX], looked at the prevalence of alleles, or gene variants, commonly associated with an increased risk of ASD. The researchers discovered that these variants were found in much larger numbers than would be expected by chance, and they suggest that this may be because they are also linked to other genes implicated in cognitive ability.
The authors write 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 it would have been selected against during human evolution.
(Score: 2, Interesting) by JoeMerchant on Tuesday March 07 2017, @05:33PM (1 child)
what constitutes autism has just expanded over the years
In-part, this is true. However, in the 1980s, Autism was a 1:2000 diagnosis, even applying today's diagnostic criteria to the population back then would not get you to the 1:68 rates we have today, or, alternatively, if you apply the 1980s diagnostic criteria to today's population, you'll get much higher than 1:2000 rates.
A combination of genetic and environmental factors have caused a change in the rate and severity of incidence. I think this is most dramatically demonstrated with displaced populations, like Africans relocated to the U.S. - in a single generation they see marked increase in autism symptoms, something they did not experience in their native environment. Within our own family, we've had "autism like" symptoms for generations, but the relative severity of the effects has taken a dramatic upturn for males born since 1970. As you say, this is too fast for simple genetics to explain.
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(Score: 0) by Anonymous Coward on Tuesday March 07 2017, @11:22PM