When autism is discussed as a culmination of denovo mutations, one thing that I dont understand is how this is reconciled with the history of the species.
It seems there is a high rate of mutations, making the non-mutant ensemble incredibly fragile. How did this work in the past? Was there significant selection against mutant varieties?
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.
Is there an understanding of the relative prevalence of each type in modern society? Thinking about changing rates of diagnosis, with common circulating variants, it seems like changes to detection and classification would be the only explanation for rate change.
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.
> 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.
I am profoundly grateful I grew up in a situation that didn't cause me to self isolate into a subculture.
I have all sorts of other problems, but I appreciate that one more as I age.
So, you could form an intimate relationship with literally anyone on Earth? Good luck getting through just the first floor of your condo block.
I haven't written anyone off, I just plain don't like most of them. Are you that different? Why do you assume my statement is a priori instead of an empirical observation? Is that how you think about your own preferences, or do you ever just kinda go "huh, I guess I really don't like $thing?"
Love is very, very specific, and I happen to be blessed with it.
> I haven't written anyone off, I just plain don't like most of them.
I'm not trying to convince you, but for anyone else reading this, especially if you're young, people are social creatures and being social will make your life better. It's frequently not easy, and often quite difficult, but so is doing 100 pushups or getting a phd or whatever. Being difficult is not the same as being bad for you.
There is a gigantic difference between "I talked to Jay and he told me he hated me and I was going to burn in hell so I decided I don't like him" and "I have decided that all normies/allistics/football fans/whatever are boring and I don't like them".
It's hard to describe the kind of mindset I'm talking about here in a YC textbox. I firmly believe that every person working at say, the checkout line in my local grocery store, know or have done genuinely interesting things and if you ask the right way, you can find those fascinating things.
That doesn't mean I actually talk to every person who rings up my groceries, or even most of them, frankly. I'm frequently tired and in an asocial mode. But there's a big difference between "I'm choosing not to interact with this person right now due to my own energy/preferences right now" and "this person is inherently bad".
> or do you ever just kinda go "huh, I guess I really don't like $thing?"
Not anyone, but i wouldn't exclude 98% of them, sight unseen. I think it is very closed minded, factually biased, and wrong. Further it sets the stage for a lot of hostility.
> Moreover, quite literally all my friends are also autspec and would never interface with someone who isn't"
It seems there is a high rate of mutations, making the non-mutant ensemble incredibly fragile. How did this work in the past? Was there significant selection against mutant varieties?