“Natural selection selects for autism” thesis revisited

To "select for" smacks of teleology. Mung

Darwin said that retarded people had mor hair. he said this was because they regressed more back to our ape ancestors. (The descent of man). So this guy seems to be saying the same thing. Autism is a regression of normal people to a ape origin. I still say these things are not that complicated. I see all retardations and autisms as just dealing with memory interference. Its just not realized how memory is the majority of our thinking at any one time. Retarded or Autistic peoples always have memory 's above average in certain things or greater attention abilities in certain things which all are about memory. Robert Byers

But I'm not sure that it does. I mean, I work in psychiatric research, and I am not the slightest bit distracted by it, except as a mild annoyance. In fact the only time I generally hear about this kind of paper is on the internet! And one of the reasons it really doesn't distract is that there have been such huge strides in genetics that we are able to see that GWAS studies, for instance, show tiny (if significant) odds ratios for any one allele, even though the disorder in question may be highly heritable. The really interesting thing about genetics and mental disorders is what the alleles in question actually do, hence the search for "endophenotypes". Many mental disorders are highly heritable but the vast majority of people with any given "risk" allele do not have the disorder. This suggests not only that a disorder is likely to be caused by many genes of small effect, but that those genes may have neutral or even beneficial effects when inherited in a different environmental and/or genetic context. For example, a gene that may contribute to a disorder in one person may protect another from a different disorder. And the disorders themselves are not usually unitary constructs anyway. So the idea that selection may favour a disorder phenotype is kind of silly. Much more likely that selection simply nudges the allele distributions along various dimensions, depending on current conditions, and that what we call "disorders" are the phenotypes that result from an disadvantageous genetic cocktail, rather than from a once-advantageous trait. And by the same token, these alleles will tend not to be "selected out" of the population, and so mental disorders will tend to persist in the population, despite the generally low reproduction rate of, for example, people with autism or schizophrenia. In other words, while I would regard evolutionary processes as important to the understanding of mental disorders, the idea that the disorders were "selected" in the past is simply naive IMO. However, the idea that alleles that slightly increase the risk of certain disorders may be, in the main, advantageous for most of us, is not, nor is the idea that the mean advantageousness or otherwise of any given allele will change over time. Regarding your last point: I'm not sure if changes of frequency of diagnosis of a disorder is necessarily an indication that a disorder is evolving. In some cases, something that wasn't a problem in one society, becomes one in a changed society; in other cases, once a condition is recognised in a severe form, it also becomes recognisable in mild, and even sub-clinical forms. Most mental disorders lie on a continuum that extends into the "normal" range. A bigger problem with autism, I think, is that the extension of the diagnosis into the milder ranges has in some ways obscured the seriousness of profound autism. Not that the extension hasn't been useful, but severe autism remains a very difficult condition. Elizabeth Liddle

Dr. Liddle, don't let me detain you from ''this post dedicated to yourself, but one observation: You are quite right that most EP is bunk. But it's not harmless bunk if it takes the place of and distracts people's attention from the search for reasonable causes and treatments of human disorders, leading to pointless theorizing about the past, resulting in unproductive disputes. For one thing, any given trait could always have been just plain negative but not fatal. The details of preliterate societies' adaptations to such traits are typically inaccessible. Autism is inconsistent with most societies' cultural values, but it is only a survival issue at the extreme end of its spectrum, where it entails global development delay. The fact that we don't need a specifically evolutionary explanation for autism is just as well, as we will probably never have one. In my view, evolution studies might more usefully concentrate on how the disease seems to be evolving today, to be much more frequent among those who definitely recognize it as a problem. O'Leary

Most evolutionary psychology that goes by the name is bunk, and based on absurdly simplistic notions about the heritability of traits that affect cognition and behaviour. Elizabeth Liddle