William Costello

And where you have massive biological differences between the sexes, we should expect some psychological differences underpinning them.

And we do find that.

You find men have a massive...

greater desire for sexual variety and sexual frequency.

My supervisor calls that the most boring replication in all of psychology now because it's just one of the biggest effect sizes.

So to put that into perspective, the effect size of the difference between men and women in terms of desire for sexual variety is about as big in magnitude as the sex difference in upper body strength between men and women.

So that's a huge psychological effect.

And in psychology, if we have an effect size that's small to medium, we're happy with that.

We'll say, OK, we'll take that as a psychological finding.

So the sex psychology differences being so huge, so robust, repeatedly replicated over and over again.

We just did it actually the other week again.

Yeah, it's just a stark phenomenon.

But it makes sense in the light of evolution when you think of the different selection pressures that would have shaped that psychology to underpin the biological differences.

Yeah, so you see a large amount of societies being preferentially polygynous, meaning one man with multiple wives.

Now, even within those societies, most mateships would have been monogamous.

But it makes sense because a woman can only benefit so much.

She can't benefit that much from having multiple husbands.

She can only get pregnant so many times once a year.

Like, if I can get multiple guys, like, word.

Perhaps, yeah, but it's harder to kind of control those men.