A lot of the behaviors by which autism is diagnosed (social communication, repetitive behaviors and restricted interests) are fairly high-level behaviors, dependent on a lot of cognitive/neural machinery beneath it. There is an idea out there that convergent behaviors that allow consistent diagnosis depends on this, as the resulting behaviors might results from differences in many different underlying processes, but the result at the higher level can be measured the same.

Analogy: Two programs can produce nearly identical behavior at the UI level, but be implemented very differently. Diagnosis operates partly at the "interface" level, but what happens underneath can differ greatly.

I feel like your initial question can be applied to a lot of things. For instance, Elher Danlos Syndrome has 13 variations depending on which gene is mutated. This include 11 known mutations and 2 catch-all categories for variations where we haven't yet found the mutation. Why are all these mutations under the same disease when they have such a range of symptoms? My guess is that it is because they were all lumped together before we had the language to talk about them as separate things or the technology to identify the causes. Going back and saying oh all these people don't have ASD or EDS or whatever but this specific thing that we have now identified might cause some disruption is research and awareness.

> what leads us to treat ASD as an actual single disorder, as opposed to a billion different individual neurological profiles?

We already do treat it as the latter. The medical definition of autism is basically just any neurodevelopmental disorder that isn’t ADHD.

This line of thinking diminishes the real struggles autistic people face. Not everyone is autistic, and it's not just a quirky set of traits. I do believe society could be better arranged for people who for whatever reason don't conform to the overculture norms, so we could talk about disability along the axis of how society privileges or disadvantages certain individuals.

The concern is that autism as a rigorous category may be useless, but that doesn't mean that autistic people are suddenly neurotypical -- a term that is more politically than scientifically oriented. People who are not autistic broadly are allistic, to be precise with language. They may be neurodivergent in other ways.

Yeah, no. Autistic people pretty reliably score high on a set of diagnostics test for example, whereas others do not.

For ASD 3 and 2 it's even easier to see it's not "everyone".

First, and foremost, the rise in autism rates is due to more sensitive instruments, a broadening of some inclusion criteria between DSM 4 and 5, more awareness of autism, less stigma associated with autism, services attached to autism diagnosis. I believe current research suggests these don't account for all the rise, but does account for most of it.

If I were to include additional biological possibilities, I'd include: a) birth control -> waiting to have children until a later age, more de novo mutations due to age. b) assortive mating, since some careers tend to attract those on the within and on the edges of the spectrum., c) perhaps controversially, and with the very little research on the subject, endocrine disruption from plastic waste exposures.

The steep rise in the last few decades is primarily due to increased awareness and expanded definition/diagnoses.

>Genetics does not explain steep raise in last a few decades.

as we built better telescopes, we found more stars

Genetic contributors to autism include:

1. common variants. Common variants are genetic variants weakly associated with autism that we all have to some degree or another, and that only result in autism given a sufficient number of them are found in a person..or at least that's a common idea and pretty well supported. These variants are inherited.

2. rare de novo variants: These are spontaneous genetic variants that the parents did not have, but there was a mutation during production of sperm, for example. Many times, rare de novo variants that occur in highly conserved genes cause tremendous neurodevelopmental problems, spanning death often prenatally, other conditions, and for, autism, most frequently with severe intellectual disability.

Common variants are heritable and common, and are part of the normal spectrum. Only with a very large load do these result in the severest conditions, I think, like intellectual disability.

Occurrence of rare de novo variants are associated with things like age of father (older, less reliable production of sperm without genetic mutations), pesticide exposures, etc.

There is also a real immune factor involved, as well as environmental exposures, which can interact with genes.

That's a good question with a neat answer: assortive mating can amplify a randomly occurring gene by sexual selection. Read on for the details.

Suppose that there was a gene that made you more likely to be good at white collar thinkwork. You meet your partner at a professional event and have a baby. The baby now has between zero and two copies of the gene. And depending on gene dominance, the probability of at least repeating the ratio of the previous generation is like 75% IIRC.

Repeat, and fold back in. Next generation, you have a couple folks with both mutations, who exhibit an even stronger affinity for quiet thoughtful work (and people). Their kids will have a 100% chance of carrying at least one copy, right? The numbers for the third gen will be even higher.

This is all massively simplified but yeah. Mendel has the answers. The picture is even clearer if you suppose multiple genes whose effects stack, which appears to be the case with the ol 'tism.

And, finally, there is the lived experience of why this happens so much. Speaking as someone on the spec, I could never imagine life partnership with an allistic person, nor can I imagine such a person putting up with my deficiencies and quirks. Moreover, quite literally all my friends are also autspec and would never interface with someone who isn't. So I believe ASD is strongly selected for by people with ASD.

But given the volumes I'd expect we are in the hockey stick armpit of an exponential curve. Like HIV bubbling away in 1950s Africa long before we even had a name for the condition, nineteenth century colonial industrialism probably quietly worked up a stock of the relevant mutations, and the mutants found each other in the grand blender of the 20th century's upheavals.

As it were, silicon valley is one of the precipitants of sex, war, and intellect.

no sarcasm tags needed unfortunately, and we autism scientists are very worried/ For example, as I submitted a few days ago: https://news.ycombinator.com/item?id=49422954

No need for your </sarcasm> tag. The United States makes repeated claims linking childhood vaccines to autism.

https://www.factcheck.org/2026/08/trump-and-rfk-jr-repeat-fa...