Ugh.

[conuly]

Well, apparently closely-spaced second-born children are more likely to be on the spectrum than first-borns or those spaced further apart.

The comments are a morass of "FOOD COLORING! DOES ANYBODY REALLY KNOW ANY GRANDPAS WITH AUTISM???" (Hi, I do!) and "TV WATCHING! THAT STUDY WAS SOOOOOO WELL DONE!" (No, it wasn't!) and "OMG, VACCINATIONS, BIG CONSPIRACY!!! (Uh-huh, you keep saying that!) but this one takes the cake:

There was study conducted to understand the risk of autism based on genealogy. The researcher chose to examined Amish people since they live in a closed society. In case you didn't know, roughly 65% of Amish have the same surname. When they first came over, their were about 300 families. Since their lifestyle isn't that appealing they rarely get new blood. They try not to get closer than 3rd cousins, but still they all pretty close. This of course increases the chance of defects greatly. So reason dictates they would have a greater percentage of autistic children.

S/he goes on from there with the same-old, same-old "Oh, the Amish don't vaccinate and they don't have autism and it's so not a coincidence!" line.

To all this, I can only say the following:

A. Logic doesn't work like that.
B. Genetics doesn't work like that.
C. YOUR PREMISES ARE ALL WRONG! Why do people have this asinine idea that the Amish don't vaccinate, or that they don't have any autism? It's not because they bothered to look up the facts for themselves - you'll notice this person has no idea what study or researcher they're talking about. No, they just repeat the same old tired lines that were worn out the first day anybody ever said them. (And they weren't true then either.)

Oh, and she also goes "As you may know, Autism was unheard of prior to 1900 (right around vaccines were widely introduced). Though many would simply say that it existed but people were simply unable to spot it back then, riiiight. "

That doesn't even merit a response. I mean, I have a few (and they're longer than two words!), but she doesn't deserve the energy.

Comments

[leora.livejournal.com]

Inbreeding leads to an increase in genetic problems that exist in the genetic pool that is being in-bred. That's how you get things like "the island of the colorblind" that Oliver Saks wrote about with an island where a rare form of colorblindness where the center of the eye that is usually predominantly made of cones, which are what perceive color, is instead made of rods, which is what most people have primarily for their peripheral vision which is more useful for spotting motion and for dark vision, but has no color vision at all. People with this condition are extremely photophobic, have less visual resolution, and no color vision (as opposed to more common types of color-blindness such as red-green where people still see colors). But the point is, it's common there, because the genes for it existed and concentrated.

But likewise, take an isolated group and if a gene is absent, say Tay-Sachs which is a risk for my ancestry but is fairly uncommon for many people's ancestries then they can inbreed to their heart's content, they can do sibling-sibling and they have a higher risk of Tay-Sachs from out-breeding than they do from inbreeding. Sure, there is the chance of it randomly mutating and re-arising in the gene pool, but that isn't any more likely because of inbreeding.

So, if autism is a purely genetic trait (which isn't clear and seems unlikely but might be... I'm really not sure at this point) then you'd have to see how prevalent the gene was in the community.

Which I know, you made that point. I just... it's baffling how people can throw such bad arguments around. I have found that with inbreeding in particular people tend to have a lot of misunderstandings. I think it's because they tend to combine a small amount of understanding of genetics with the incest taboo and squick. Even though a single generation of incest isn't actually genetically necessarily a risk to the children (unless you have good reason to believe your family carries a fairly dangerous recessive). And less squicky matings but carried out over multiple generations can actually be a problem, if they do involve cumulative narrowing of the gene pool. Although it does also maximize good traits... see purebreds/thoroughbreds for some of the best and worst of both ends of that.

Oh wait, sorry, logic, reason, facts, data... what on Earth am I doing on the internet?

[leora.livejournal.com]

On a side note, if I were guessing, I'd probably guess that autism is a trait that is a combination of genetics and prenatal environment. It seems to be set pretty early, but I doubt it's 100% genetic. But a lot of things are affected by the prenatal environment, and that is when the brain is doing its first basic growth. But I'm waiting for far more evidence before I hold any hypothesis with any real strength.

[conuly]

If I had to guess I'd say that autism is highly genetic (and I have the anecdotes to "prove" it!), probably related to environment... and quite probably has multiple exact causes that we casually lump together because it all seems the same on the surface.

[leora.livejournal.com]

Well, it definitely runs in families, so there is clearly a strong genetic component. But it doesn't seem 100% genetic to me. Multiple environmental triggers is certainly possible. And if you're just leaving "environment" open, then it could either be prenatal or postnatal. But it really can't go too far into postnatal, because it really does seem to get set pretty early. You don't hear about adults or even older children developing autism with no earlier signs. Sure, you hear about later diagnoses, but generally then you also hear about earlier symptoms that weren't put together.

And I don't think that's misdiagnosing. I don't think this is the sort of thing people can develop too far into brain development.

But yes, definitely a strong genetic component, since autistic children often have a parent on the spectrum or at least one who recognizes several of those symptoms in themselves.

[conuly]

What I said to this person is that theoretically you could keep on inbreeding and, through amazing luck with your ancestors, hit the genetic lottery - long lifespan and good looks too!

In all seriousness I shudder to imagine the odds on that deal, it's gotta be worse than one-in-a-million, but if you pick your bottleneck very carefully it can't be absolutely impossible, right?

I think it's because they tend to combine a small amount of understanding of genetics with the incest taboo and squick. Even though a single generation of incest isn't actually genetically necessarily a risk to the children (unless you have good reason to believe your family carries a fairly dangerous recessive).

Yeah, I've never understood why some people honestly believe that if you fuck your sibling, half-sibling, first cousin you're going to end up with a four-armed baby. Genetics still doesn't work like that! It'd be funny if it did, in fact.

[leora.livejournal.com]

The two-headed babies thing, that I always heard (variant on four-armed, I suppose) always confused me until I realized where it came from... conjoined twins. It's a very old wive's tale based on conjoined twins, and it isn't even at all related to inbreeding.

Once I realized that, I really disliked the meme, since among other things, it's very disrespectful to conjoined twins.

[marveen.livejournal.com]

Yeah, cf. the SF story "If All Men Were Brothers, Would You Let One Marry Your Sister?"

The author points out that inbreeding has been used for centuries to bring out desired traits in livestock, without deformities or idiocy cropping up in the first generation. (Although some lines of purebreds are starting to make me wonder about the idiocy part, and undesirable traits get accentuated too.)