[1] More specifically, with handling sets of sensory stimuli that society expects everyone to be able to cope with. It's a somewhat open question to what extent "disability", in this case, means "different from what society expects". (Oddly enough, I don't think this even used to be part of the official diagnostic criteria despite being really common.)
In selecting for intelligence a harm is acquired: the risk of sevre autism.
So "simplistic perception" is not correct. By selecting for intelligence, we incidentally acquire a problem.
Not sure what you mean here. You can have simultaneous selection for and against 'autism spectrum disorder', if it is heterogeneous. If for example it is a mix of actual social dysfunctionality/brain damage and greater intelligence/abstracting/systematizing, you could have selection against the former and selection for the former, and the net measured effect on the mixture could go either way.
(This is not as odd as it sounds. We seem to see something very similar with the Neuroticism trait: the overall trait appear bad for you, which makes sense since it's usually seen as not very good to have a lot of, but if you break it down into its 'facets', some of them are good for you: "Genetic contribution to two factors of neuroticism is associated with affluence, better health, and longer life" http://biorxiv.org/content/early/2017/06/06/146787 , Hill et al 2017. It's analogous to how there are minimal sex differences on Big Five personality when examined at the Big Five factor level, but when broken down to their sub-factors, sex differences jump out at you.)
That is directly at odds with the analysis in the Grove et al. paper; the genetic basis of increased educational attainment is distinct from that associated with 'severe' autism.
I think this is a case of wanting to see patterns that aren't necessarily there; we'd like to see a nice even spectrum of behavior, with undesirable extremes at the ends. It's a nice reductive interpretation of complicated data. The problem is that it doesn't seem to fit. At least so far; genomic studies are very useful, especially as a starting point, but ultimately mechanistic explanations that generate testable genetic hypotheses are the gold standard for biology. And for good reason.
Still, given that what evidence exists does suggest a different framework, I'd be very hesitant to conclude that there is a trade-off.
> We find that the observed excess in ASD subjects of alleles positively associated with education attainment is confined to Asperger’s and childhood autism, and it is not seen here in atypical autism nor in other/unspecified PDD.
In simple terms: looking broadly, there appears to be meaningful genetic differences between diagnoses of childhood autism and Asperger's vs. pervasive developmental disorders (in lay terms, I'd call this 'full blown autism'). Basically, the genetic stuff that's linked to educational attainment is different from the stuff that leads to 'severe' autism.
This is especially interesting because these potentially 'good' and 'bad' traits are likely affecting the same time and location of development:
> Interestingly, both common and rare variation in ASD preferentially affects genes expressed during corticogenesis, highlighting a potential spatiotemporal convergence of genetic risk on this specific developmental epoch, despite the disorder’s profound genetic heterogeneity.
Worth noting that this is a pretty significant paper and serves as a solid foothold for the 'not a trade-off' interpretation of intelligence vs. autistic behavior. I.e., the latter is not necessarily a consequence of 'too much' of the former.
Look: simply being smart is not in and of itself a symptom of ASD. There are a number of symptoms associated with the spectrum that actually have very little to do with intellectual ability. It's inappropriate and factually wrong to make the statement that logical and systematic thinking is symptomatic of ASD.
And what if it's true for a short period of time until a new mutation arises that eliminates the double edged sword? Most of our adaptations are really really old. They've had enough time to "perfect" themselves.
What if evolution isn't clean or pretty? What if it's a messy business where a gene arises that gives a small edge, but brings with it a host of problems. It'll still spread because of that edge and it may take millions of years to sort out and eliminate the side-effects.
Because it doesn't. That sort of pleiotropy just is not common, empirically, in humans. Hundreds or thousands of genetic correlations tend to confirm this: there are loads of free lunches. Why is that? A lot of it looks like relaxed selection (eg my other submission shows that our ancestors thousands of years ago appear to have had substantially lower genetic risk of disease because it was decreasing over time, but has reversed), the slowness of selection given the small effect sizes vs the constant incoming stream of new mutations, and the demographic history of humanity of massive expansion from a small starting population based on migration of also tiny groups.
If I understood you correctly, environment pressure relaxed for former traits. But then the new human environment caused the presure for other set of mutations to kick in, even if they're counterproductive for old environment...
There really is no 'hiding' in evolution; if a trait has deleterious effects, even only in specific genetic or environmental contexts, then they are felt. It is this brutally simple force that permits such complex systems to function effectively.
I see it as almost axiomatically true, but I think the difference is you are taking a narrow definition of what constitutes a "bad" trait. Examples:
- Immune system: protects us from microbes but contributes to atherosclerosis, autoimmunity, and age-associated chronic inflammation
- Mitochondria: Generates ATP but also oxidative stress
- Infant brain size: makes humans as smart as we are but increases maternal mortality
- Body mass/volume: gives greater protection against predation but increases energy requirements
- Intelligence & brain volume: improves on-the-fly adaptability but costs a lot of energy to run
In the most general case, any gain-of-function adaptation which adds a new protein/organelle/limb/etc has a built-in bad trait which is that it costs resources to produce, DNA to maintain, and also adds another potential point of failure. The equilibrium point between benefit and costs is where evolution will land.
So I would argue that the reason we have X IQ points or Y neurons is exactly the same reason we have Z mitochondria: any more and the costs would have exceeded the benefits in the ancestral environment. The fact that we can seemingly get more benefits than costs from increased intelligence now merely reflects the fact that our environment has changed.
Also, JBS Haldane wrote an anti-eugenics book many years ago which used exactly this sort of argument.
if it were true, we would see all sorts of genetic
correlations where one good trait systematically
boosts a bad trait