Huge, thin mirrors in orbit over the equator that reflect light that would have hit the equator to the area of earth experiencing winter.

And they also vary CO2 levels systematically by geography as well; if that was enough for a detectable effect on IQ, then the lower CO2 levels around Denver should make the rest of us at lower altitudes, such as sea level, look obviously handicapped. If you believe the altitude point refutes effects of oxygen, then it must refute effects of carbon dioxide and nitrogen as well...

Which is part of my original point about implausible effect sizes: the causal effect is underidentified, but whether it's oxygen or CO2 or nitrogen, it is so large that we should be able to see its repercussions all over in things like the weather (or altitude, yes).

Small proportional changes seem unlikely to drive big effects, unless there is some feedback mechanism that is keeping the level precisely balanced.

Such as in the body, dealing with tightly regulated and critical aspects of metabolism like oxygen consumption.

But 1% changes in oxygen should be happening all over the place.

Perhaps they are. You don't know the effect because the existing experiments do not vary or hold constant oxygen levels. All you see is the net average effect, without any sort of partitioning among causes.

It doesn't matter if some of the group differences are genetic in origin, given that others are not, we can still resolve those.

Those can be resolved but they will not make nearly as large a difference as currently expected, where current ideologies hold that all of that 3-190x per capita difference is due to environmental conditions, history, and racism. HBD implies that, just as with individual differences and the systematic failure of welfare and education randomized experiments to 'close the gap', we can expect this futility to occur on a country-level basis at some level of development. Countries like China (maybe) and North Korea (definitely) will be predicted to escape their current poverty levels with appropriate interventions... and countries like Subsaharan Africa to possibly not escape. (Which countries can be made more concrete in a HBD context by taking Piffer's country/group-level polygenic scores and looking at the residuals of a GDP/score regression for the countries which most over and underperform; the former can be predicted to not grow substantially, and the latter can be predicted to grow substantially.)

Remember how heritability works. If environments improve, genetics will explain more and more of variance. It's Liebig's barrel. Shared-environment in the USA is very small.

Do the implications here change?

Yes, because those environmental factors are causally downstream and cannot be improved without the locals. As development aid has discovered again and again, you cannot force improvements on a country. Pakistan, for example, is so dysfunctional and clannish that iodization and polio programs have had serious trouble making any headway.

The steps we should take don't depend on HBD being true or false.

Yes, they do! These causal models are fundamentally different. If genetics is a major limiting factor, iodine and all other environmental factors are not going to help past a certain level of development. (You can feed some Americans or New Zealanders iodine supplements, but it won't give them +10 IQ points even though they are probably somewhat deficient). If genetics is the major limiting factor, then at a certain point, you are basically polishing a turd and this can either be accepted or more radical interventions must be considered.

What are your favorite puns?

This looks like a special case of a failure of intentionality. If a child knows where the marble is, they've managed first-order intentionality, but if they don't realize that Sally doesn't know where the marble is, they've failed at second order.

The orders go higher, though, and it's not obvious how much higher humans can naturally go. If

Bob thinks about "What does Alice think about Bob?" and on rare occasions "What does Alice think Bob thinks about Alice?" but will not organically reason "What does Alice think Bob thinks about Alice's model of Bob?"

then Bob can handle second and third but can't easily handle fourth order intentionality.

It may be a useful writing skill to be comfortable with intentionality at one level higher than your audience.

all the good ideas have turned out to be simple

Yeah, right.

[EDITED to add:] I don't disagree with the overall thrust of the post, and I agree that a lot of good scientific ideas have turned out to be simple. But that was one step too much hyperbole for me.

I loved your post, but I also think metatroll's comment is funny. I don't think it's anything but a joke.

It's circular, and square.

That's literally all there is. I can't imagine it visually, the way I usually would. Wonder why. :P

There exists an irrational number which is 100 minus delta where delta is infinitesimally small. In my celestial language we call it "Bob". I choose Bob. Also I name the person who recognizes that the increase in utility between a 9 in the googleplex decimal place and a 9 in the googleplex+1 decimal place is not worth the time it takes to consider its value, and who therefore goes out to spend his utility on blackjack and hookers displays greater rationality than the person who does not.

Seriously, though, isn't this more of an infinity paradox rather than an indictment on perfect rationality? There are areas where the ability to mathematically calculate breaks down, ie naked singularities, Uncertainty Principle, as well as infinity. Isn't this more the issue at hand: that we can't be perfectly rational where we can't calculate precisely?