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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) by stormwyrm on Tuesday March 07 2017, @04:22PM (3 children)
The criteria of what constitutes autism has just expanded over the years, and diagnosis has also gotten more aggressive. We weren't looking as hard for autism in the past. The harder you look for something, the more of it you will tend to find, and you'll find even more of it if you broaden the criteria of your search.
http://scienceblogs.com/insolence/2017/01/25/another-reminder-that-there-is-no-autism-epidemic/ [scienceblogs.com]
If there was a genetic selection for autism, it likely took place a lot longer than a mere decade or two ago. It literally takes generations for genetic selection to happen, so the timeframe is more like centuries.
Numquam ponenda est pluralitas sine necessitate.
(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.
Україна досі не є частиною Росії Слава Україні🌻 https://news.stanford.edu/2023/02/17/will-russia-ukraine-war-end
(Score: 0) by Anonymous Coward on Tuesday March 07 2017, @11:22PM
(Score: 2) by dry on Wednesday March 08 2017, @02:24AM
While they weren't looking for autism as hard in the past, they still noticed the dysfunctional. I got diagnosed as brain damaged due to shortage of oxygen at birth back when I was evaluated in 1967. During my sons diagnosis for basically the same symptoms, the Doctors and researchers were very interested in the relationship between my son and I, as in blood samples for genetic tests and they seemed to just automatically accept that I'm autistic.