Proof of genetic component intelligence + study proposal

[QwertyDavid]

After finishing all the podcasts on intelligence, I was thinking today:

(NB: I talk about VARIATION, not Averages, variation just means the average difference in abilities. So you could have 2x5, the variation is 0 and the average is 5, you could also have 10 and 0, the variation is super high but the average is still 5). There are average differences in traits for men and women, but how does this relate to the variation?

(NB 2: You probably need to have some knowledge of genetics AND basic biology)

- Women have a higher absolute number of genes coding for abilities (X chromosome is bigger than Y, also recessive X alleles have a higher chance of showing in the phenotype in a man because they just have 1 X)

-This is a real genetic difference which is true in every man/women, while there are genetic differences between races, in theory, you could get 2 exactly the same people from different races without those races interbreeding (chances are almost 0, but it's possible in theory, but the X and Y difference will be there for everyone)

-Because of that higher number of genes, the female population is more stable. The extreme for every trait is a man (shortest person, fattest person, tallest person, thinnest person, fastest person, strongest person, smartest person, dumbest person (probably) etc....), so if the variation in the male population is bigger, there is almost certainly a genetic component. The question now becomes: How much can the variation tell us? 

- This can be found in IQ too (male IQ has higher variation)

 

My question/study proposal:

We could run a formula like this:
Calculate the number of genes in a male (maybe coding for a specific ability, like intelligence)

Calculate the number of genes in a female (" ")

You would be able to have a ratio of Male genes:Female genes (and calculate the standard deviation of allele frequency),

if this ratio is similar in the variation (male variation:female variation), the trait would probably be highly genetic (correct me if I'm wrong)

 

A second question: Is the variation of males and females more similar in more environment based traits? If yes, we don't need to identify all the "intelligence genes", we could just look at the ratio of Male:Female variation, and compare that to other traits. Height variation (height is highly genetic), muscle mass variation (more environment based, you can train your muscles, they'll get bigger), and other ones. If the variation ratio is more similar to that of height IQ will probably be more genetic.

 

 

So: A study design in which we compare the variation ratio (male variation:female variation) of men and women, would that help us to see which traits are more genetic and which aren't (I think maybe, I don't know what the environment has for an impact on variation, women are more risico averse, so this could also have impact on the variation)

 

[QwertyDavid]

So yes, I know there are other empirical studies proving that IQ is probably mostly genetic, but this is an underlying mechanism which proves it (without even looking at genes).

[ofd]

Doesn't work for a simple reason: during the fetal development in mammals one of the X-chromosomes is deactivated randomly.

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

[QwertyDavid]

That still doesn't take away the fact that they have 2xX, yes one is inactive but it's still there. They still have more genes right?

[ofd]

Quote

They still have more genes right?

When I was at school I learned that a gene has to be active to be counted as such, it has to be read out and actually serve as a blueprint for proteins and what not, this may have changed though or I may misremember. In any case, males have more (active) genes.

I am not an expert when it comes to testing the heritability of IQ, but Alternative Hypothesis has some well documented videos about the topic.