Missing Heritability

Once again, I find that I know very little.  Much More Than You Wanted to Know over at ACX. I hope my 20 years of misleading you has been much less than half. It is as long an article as you would predict ACX would devote to it. But as it flips everything up in the air and we are still waiting for the fried goods to come down, it would sort of have to be.  

There is a whole new group of Anti-Hereditarians over the last decade or so, who have applied very strict standards to what we can predict from genes, causing our previous estimates to look much more fragile. 

It seems like we have to accept one of three possibilities:

Either something is wrong with twin studies.

Or something is wrong with Sib-Regression and RDR (and then we can explain away GWAS and GREML by saying they’re missing rare variants).

Or something is wrong with how we’re thinking about this topic and comparing things. 

The hereditarians are fighting back with some compelling evidence that there are some things we do know by gross measurement, even if we are unable to make that more granular. Dr. Alexander gives a good personal example.

 During residency, I spent a few months working in a child psychiatric hospital for the worst of the worst - kids who committed murder or rape or something before age 18. Many of these children had similar stories: they were taken from their parents just after birth because the parents were criminals/drug addicts/in jail/abusing them. Then they were adopted out to some extremely nice Christian family whose church told them that God wanted them to help poor little children in need. Then they promptly proceeded to commit crime / get addicted to drugs / go to jail / abuse people, all while those families’ biological children were goody-goodies who never got so much as a school detention. When I met with the families, they would always be surprised that things had gone so badly, insisting that they’d raised them exactly like their own son/daughter and taught them good Christian morals. I had to resist the urge to shove a pile of twin studies in their face. This has left me convinced that behavioral traits are highly heritable to a level that it would be hard for any study to contradict.

 (I am a big Cremieux fan, BTW.) 

The Anti-Hereditarians strike back!

 Sib-Regression is a clever way of avoiding most biases. Its independent variable - the degree to which some sibling pairs end up with slightly more shared genes than others - is even more random and exogenous than the difference between fraternal and identical twins. It can sometimes have biases related to assortative mating (which would falsely push heritability down), but otherwise it’s pretty good. RDR has many of the same advantages, and allows more diverse relationships and so larger sample sizes. It’s hard to think of ways these methods could be wildly off.

And the "maybe we are just looking at this all wrong" group has some power in it as well.  Some traits like intelligence (IQ) and educational attainment (EA), where we (think we) can easily see how they must be related, but also can easily see they would have some wild variance may be related just about as much as we have been measuring, but for completely different reasons, so that our further testing is leading us down false paths.

Each of those possibilities would mean we have a lot of humble thinking to do.  So I will start by learning more humility, as that is one thing that is going to clearly be needed.