> One of the reasons is, half their cells are using one X chromosome and half are using the other, so they're more likely to get their performance dragged down by deleterious mutations.

This statement is wrong 2x.

1. Lyonization is a process of inactivation that happens early in embryotic development so only one X is dominant in all somatic cells.

2. The chromatin packed X is not completely inactive, so if the dominant X has a deleterious variant the other X can sometime confer protection. Without a good copy of an X allele men getting X-linked disorder is a foregone conclusion. Women on the other hand suffer from X-linked disorders approximately 50-25% as often.

Also there is no evidence linking any of this to math ability

It's not "disorders" but anything that affects math ability. This is plain regression to the mean. If half your cells would make you capable of being an IMO gold medalist, if the whole brain were made from them, but the other half would make relatively stupid so that you could only barely qualify for the USAMO (~top 300 in USA or so), guess what making a brain from the combination of the two will get you.

Like I pointed out above, thats not how it works. And if it were, then women would be at an advantage. If genetics confers any difference in math ability, it's due to the Y chromosome. Period.

What isn't how it works? Why would women be at an advantage? There's clear evidence that different groups of cells are using one X chromosome versus the other. You can see this in cats, and you can see this in mammals' brains using fluorescent genes. If you want to claim it makes women more likely to be in the top 0.001%, you're by all means welcome to explain why. But you haven't.

Edit: You know, it occurs to me maybe you aren't trying to put together statements that make any sense, because when you said "1. Lyonization is a process of inactivation that happens early in embryotic development so only one X is dominant in all somatic cells," you were acting like that's a support for your argument when it's in fact just a description of X-chromosome inactivation. Unless you meant that all cells pick the same chromosome, in which case you're just wrong.

In any case I direct the readers to this New York Times article which has a picture of a slice of the brain with different X chromosomes inactivated. Readers can draw their own conclusion about how this affects the probability of being in the top 0.001% of ability at anything.

https://mobile.nytimes.com/2014/01/21/science/seeing-x-chrom...

I read your response yesterday evening, and was just going to take the lesson and move on. But that wouldn't be fair to you.

You are right. I was wrong.

I was taught that X inactivation happens so early in development (I think pre-neural tube, no?? if so, that's like what, 200 total cells?) that all neurons, or at least all neural subtypes (e.g. Purkinje, pyramidal, basket, etc) all have the same dominant X chr.

When I saw the picture in the NYT article you linked, I was immediately like- no. fucking. way! Well, anyway. I'm sorry about that; and I appreciate the enlightenment.

That said, you should check out figure 8 in the original article. I'd be interested to know what you think. Here's a direct link:

https://www.sciencedirect.com/science/article/pii/S089662731...

(the paragraph just above the figure is helpful to read)

>> One of the reasons is, half their cells are using one X chromosome and half are using the other, so they're more likely to get their performance dragged down by deleterious mutations.

That sounds like something has been severely misunderstood by someone, possibly even me. Are you a biologist?

See https://en.m.wikipedia.org/wiki/X-inactivation

With respect, this does not answer my question: are you a biologist?

The fluorescent proteins don't lie.

Yes, I'm sure they were brought up proper and are very honest, but in order to understand them you need the relevant training. Looking at your profile I can't see that you have that sort of background. So I don't think your confidence that you know what's going on is justified.

Or, like the saying goes- a little knowledge is a dangerous thing.