Catherine Page Harden

But most of the reasons why people are taller or shorter is because there's thousands of genes scattered throughout the genome

That might make you a millimeter taller or a millimeter shorter.

But even though each one of those genes only has a tiny effect, you could have many, many, many height-increasing genes, and then you're going to end up on the tails.

And it's the same sort of thing for behavior.

So we're looking at things that are what are called massively polygenic, so poly meaning many,

Genic meaning, obviously, genes.

So there's many, many genes involved.

Each one of them is just like adding a little tiny hair to the scale.

But we have a large DNA sequence, and we have a lot of genetic variants.

And so they can add up so that it makes a large difference at the tails of the distribution.

So I think you've just said the most controversial word of the podcast, and that's the word cause, which is a word that not even philosophers of science agree on and not even different branches of science agree on.

So I'm trained as a psychologist, as a social scientist.

So we intend to think of causes as probabilistic difference makers.

So if you inherited something, it makes a difference to the probability of showing a behavior.

And our best evidence that these genes are actually causal is that we see that they make a difference even within families.

So if the genes are associated with behavior, even when comparing between siblings or even when controlling for your parents' genes, that's pretty good evidence that those genes are operating causally.

But everything we're talking about with human behavior doesn't have just one cause.

So it's not nature or nurture, genes or environment.

It's always genes and the prenatal environment.

and the social structures that you're being raised in, and your access to material resources, and poverty, and lead exposure, the idea that we're going to find the smoking gun, the thing that is the cause of behavior, just isn't realistic.