Autism and Evolution

I am not dismissing the idea that environmental causes may be at play... but be VERY VERY cautious when throwing around charts like that.

http://www.snopes.com/medical/toxins/glyphosate.asp

Correlation != Causation and not every scientist is an expert on Autism/Genetics/Biology.

"Even disregarding the sloppy mathematics, the claim's very basis (that glyphosate is the cause of a perceived increase in autism) is unsupported. No mention was made of how glyphosate was isolated and shown to be a cause (or even a factor) in some or any cases of autism in the article. No autism spikes near agricultural facilities were described, nor was any definitive causative link at all cited by the article (and presumably, Seneff) to back up the purported link between glyphosate and autism rates anywhere other than the imaginations of those making the claim. The single link of merit made within the article (to a USDA report) made absolutely no mention of autism at all but was misleadingly arranged to suggest a connection.

What the claim seemed to hinge on largely was a correlation/causation fallacy: Because [unclear activity involving glyphosate] occurred, a corresponding rise in autism diagnoses must be due to that unspecified issue with glyphosate. Claims of a similar nature have been dispelled with graphs like the following that show how difficult (or simple) it is to "prove" any one cause correlates with any one effect:"

It doesn't need to be one or the other. Genetics can predispose somebody to be more vulnerable to certain environmental factors. They will not show any symptoms unless those environmental factors are present, but there's still genetics involved.

And of course there's this whole field called epigenetics that studies how the same genes can be expressed differently based on environmental factors.

There are a lot of potential candidates... too many to be honest, and a lot of them are related to basic economic activities. History shows that environmental issues driven by economics aren't solved until an alternative comes along and is adopted; the problems of dead horses and horse dung in NYC streets were solved by... the automobile.

I'm put in mind of the recent paper posted on HN regarding magnetic nanoparticles being found in human brains. Unrelated to autism (probably) is the increasing study of prions and in general, maladaptive protein synthesis. What isn't known about these issues could fill volumes.

My cousin had debilitating autism that was greatly diminished by removing wheat germ from his diet, so I partially buy the environmental take, but on the other hand it is a disease that is correlated with parental IQ, where a higher IQ leads to more likely incidence of autism. I don't think it's a coincidence that the rise of co-sexed secondary education and finer grained sorting with institutions like Harvard and MIT getting an even more concentrated amount of intelligent people.

It is not prevalence that is growing exponentially, it is diagnosis.

> I don't quite buy that autism will be shown to be genetic. I think it's an environmental factor. The rate of increase in autism is pretty much exponential:

You're confusing increase in diagnosis versus increase in autism. This confusion is the whole basis of the "autism epidemic" claim.

Another possible explanation for such a rise that I have seen repeatedly given is that the methods and basis for diagnosis changed in the early 90s.

http://www.forbes.com/sites/tarahaelle/2015/01/05/majority-o...

Its also discussed here on Fresh Air by the author of a book on Autism called Neurotribes.

" But because no one really explained to parents exactly what had happened - that the diagnosis had been completely rewritten - that, you know, autism by the end of the 1980s and the early 1990s was not your grandfather's autism, you could say. It was much more broadly defined because no one ever explained to the lay public what had happened with the diagnosis. When the numbers started going up, parents very understandably became very alarmed. And the media was sort of blindsided by the sudden spike in diagnoses."

http://www.npr.org/2016/09/09/493148713/neurotribes-examines...

When the autism diagnostic criteria were broadened in the DSM, the people making that change predicted that we would see this rise in diagnostic rates. That was the intent, to help a broader range of people. It's played out slowly as clinicians and schools were retrained. There's also been an increasing incentive to diagnose as autism in addition to intellectual disability when possible, because insurance companies and schools will do a lot more if it's labeled autism.

So we've seen that shift. The diagnostic criteria changed a lot, not just a little, over time.

By coincidence, Wakefield launched his fraudulent crap about vaccines a few years after the criteria were broadened, and that became the popular explanation rather than the fact that the criteria changed. Belief in his BS is perhaps fading but it's still around.

The "epidemic" was predicted and an intentional outcome of the DSM criteria change, though.

If you hang out with a bunch of families with autistic kids, it's very obviously inherited in a large fraction of cases, because the kids are so much like their parents.

Another large fraction is likely genetic in the sense of "de novo" mutation, rather than inherited genes. There's likely also a group of environmental cases, mostly prenatal environmental factors.

Because social function depends on many coordinated aspects of human cognition, any condition that has a fairly global effect on the brain can create traits meeting the autism diagnostic criteria. The criteria are very broad, with many different ways to meet them.

It's important to realize that autism is a broad category, not a single condition, and no proposed single gene or environmental factor ever seems to relate to more than a few percent of cases. https://intellectualizing.net/2013/12/17/book-rethinking-aut...

Some of those causes could well be new to the modern world, but the changing diagnostic criteria do explain most of the expansion in diagnoses already, so there isn't a lot of evidence that we need to be looking for something novel to explain the increased diagnoses.

What if the markers are recessive and the social fabric today means more people with the recessive genes procreate?

I disagree, I find it intuitive that autism is genetic. View autism as a genetically induced alternate brain development. Usually it doesn't pan out, but sometimes it leads to innovation that wouldn't otherwise be possible. This leads to a survival advantage for a given subpopulation, which is sufficient for natural selection.

Simple TED talk explaining what we know and what we know doesn't cause Autism. From 2014.

Takeaway: it's a mix of both genetics and environment.

https://www.ted.com/talks/wendy_chung_autism_what_we_know_an...

I'd strongly recommend you listen to Steve Silberman, Neurotribes author, on Fresh Air:

http://www.npr.org/sections/health-shots/2015/09/02/43674237...

(Audio controls in the left margin.)

He addresses that a fair bit, mentioning that autism is one of the most heritable conditions, and talking a lot about the history of the diagnosis and how it was artificially narrow for a long time.

Personally, my bet is that we'll come to see a lot of autism diagnosis as part of a broader pattern of medicalization of deviance from the norm. And that even the forms we eventually decide are harmful have for nerds the same relationship that sickle-cell anemia does to malaria resistance: a trait that is useful in small doses but can be harmful in large ones.

If there is an actual increase, I'd bet on it being due to stronger assortative mating that has come as mate choice has less to do with geographic factors and more with education and workplace.

Small correction. We knew full well that lead was toxic, with adverse cognitive effects, before introducing it to gasoline.

https://www.wired.com/2013/01/looney-gas-and-lead-poisoning-...

FACT: Asperger's runs in families. Nuff said.

>>>> The rate of increase in autism is pretty much exponential

That chart shows the rate of increase in autism diagnosis, which is not the same.

The incredible part about that detail would be that in any other animal much of Schizophrenia's symptoms would be subclinical, in that language and socialization expresses most of Schizophrenia's detriments.

The paper is really about emergence and transmission of the disorder, and not so much about why humans find faults in those afflicted by it. But consider solitary animals, or apex predators. That they'd be schizophrenic, and construct distorted understandings of the world around them probably wouldn't matter, as long as they manage to hunt for food and produce offspring. No one would care about what a bear thinks of the origin of the universe, or how realistic its outlook of its own future is.

I realize that Schizophrenia has other debilitating effects, but it also affects people in varying degrees.

OTOH, a world full of people with autism might never be able to come together and build large group projects. Autism might work well for creating in the computer+Internet age (but I have doubts that non-autism traits are totally unnecessary), but much less likely to work in lower-tech society.

I like this.

Personally, I am not big on better/worse, but just different. E.g., we could look at white people as a weird mutation of true humans, one shockingly prone to skin cancer. Of course, as a white person, I'd rather see myself as an equally valid kind of human.

For a while I've been wondering what the DSM would look like if non-neurotypical people were in the majority. If we had a diganostic category for what we now call "normal" levels of sociality, selfishness, manipulation, violence, etc.

There's no such thing as being more evolved. More fit, maybe. We're all as evolved as each other.

Otherwise you end up having to debate whether people with lactose tolerance are more evolved than people without, and so on. It gets messy.

Also, the history of eugenics. Autistic people have been sterilized and institutionalized, really quite recently. So I'm allergic to talk about people being more or less evolved.

Why do you have to be something different, the next thing after? Other highly coordinated organisms like ants, bees and termites have evolved morphologically distinct developmental paths. Couldn't autistics just be in a sense extreme examples of a subtype of human that serves the purpose of disrupting group-think and introducing new ideas into the culture?

Did you say "fans are slans"?

Evolution isn't directed.

dragonwriter is right in general sense. We can evaluate it, though, from our own perspective. It's a step forward in terms of intelligence and stability in world. It's a giant leap backward in terms of success or happiness in a world of non-autistic people. Evolution would also consider it a negative in that autistics get laid and reproduce less than non-autistics. They also are more likely to loose in competition in corporations, battlefields, and jungles. So, it's a net loss overall for evolution's main function but autistics persist for one reason or another.

My guess is that the mutations are retained as variation in the population because having some small subset of them probably results in divergent thinking which can increase overall group survival. Autistic spectrum disorder individuals result from having too many of these mutations, such that neural activity patterns find a stable equilibrium outside of "normal" (think strange attractors in system dynamics).

Either genes survive or they don't. There's no forwards or backwards.

That does support non-genetic factors to some extent, but the existence of such twins matters less than their frequency, because twins don't always have identical DNA (mutations can occur after they separate).

you mean "identical". both identical twins and fraternal twins are biological twins.

(Forgot to explicitly say, the failure modes are different: an inactivation that inhibits gracefully (simply forgetting) vs activation independent of actual signal (spurious thought). False negatives vs false positives.)