Can progressives be convinced that genetics matters?

The catch here would be thinking in distributions, and from that separating individuals from said distributions.

A current topic would be representation within a given domain. Particularly since in most representation cases (high paying jobs, celebrities, top universities, etc), we're already looking at the tails of the distribution. There, small shifts can heavily affect the quantity of users in the right tail, especially for domains with stronger requirements (see your case with the runners).

Of course I won't try to discount potential cultural impact, but anyone trying to sell you a story of how it's all nature or all nurture is typically spouting bullshit.

> I found very large improvements in working memory from taking 20-minute afternoon naps

Sure. My ability to do anything also drops to near zero if I don't sleep enough. Yet I have not found unlimited increases in capability if sleep more and more...

> modafinil

Yeah, drugs are a quite different beast. Doping happens when individual athlete realizes they have hit the limits what their "natural" biology can do and yet still are not going to win the competition.

Yes and no, and yes again. And no.

For any given trait X, the question about how much it is "inherited/genetic" or "environmental" is a commonly used shorthand, even amongst professionals, but it can be subtly misleading. All traits are 100% inherited, and all traits are 100% environmental. What do I mean by this? How is the ability to speak Russian genetic? How is the colour of your hair environmental?

Well, put it this way: is the difference between a human child brought up in a Russian family and their pet dog who has lived with them for the same time genetic or environmental? And what is the difference between a pair of identical twins, one of whom bleached their hair with peroxide–genetic or environmental?

The above are of course exaggerations, but they're just obvious examples. The correct way of phrasing the question is this: given a population A, what percentage of the variability of trait X is inherited and what percentage is environmental? Given the population of mammals, is the ability to speak Russian mainly genetic? Yes. Given a pair of identical twins, is any difference in their hair colour environmental? Also yes.

So, to the question as to how much of a decline in intelligence can be accounted to malnourishment throughout life (and how much to other environmental factors, genetics, etc.) we need to specify what population we're talking about. I'd be willing to bet that:

1- the variability in intelligence due to malnourishment in the population of middle-to-upper class children is negligible,

2- the variability in intelligence due to malnourishment in the entire child population of a developed country is detectable,

3- ...and the variability in intelligence in the due to malnourishment in the worldwide child population is significantly higher.

I think Charles Murray's position is misrepresented here. At least in his latest book (Facing reality), he doesn't talk about genetics (of which he is not a specialist), but about inheritable characteristics. His point is that you don't know where the cursor is between genes and early education/environment, but since you can't take children away from their parents at birth, the distinction doesn't really matter from a public policy point of view.

He doesn't say that genes (or early environment) is the only thing that matters either, and points at evolution in the IQ distribution over time, and takes the argument that if you were to put an "asian tigger mum" behind each children, you would most likely get an impact on scores.

For those interested, his debate with Coleman Hughes is interesting [1]. Coleman makes an good objection. He says that these studies on variations in IQ distributions may or may not be correct, but that we shouldn't publicise them because most people are incapable of thinking in term of distributions, and will treat an individual differently based on one of the metrics (mean, percentile, standard deviation) of whichever way you cut the population. I am conflicted on that. On one side I oppose the idea that you shouldn't look at the facts because the facts could be misused (the "chemistry is bad because Zyklon B" argument). On the other hand I have seen enough educated and smart enough people incapable of thinking in term of distribution to acknowledge that Coleman has a point.

[1] https://www.youtube.com/watch?v=OE5QcD_12fQ

If you take someone with an IQ of 100 and train them for a decade I think it's still very unlikely that they would become an elite chess player/musician/etc.

I see intelligence mostly as your rate of learning. That means you're competing with people who will get better faster than you. The only way to beat that is to outwork them, but there are only so many hours in the day.