Darby Saxbe

So having jacked up testosterone is not that helpful to us when we're in a context that doesn't require that competition.

Exactly.

And so even in birds, you see higher testosterone at the start of breeding season when birds are like trying to find a chick.

I mean, a female.

That's where we got it.

Testosterone levels will drop once a male has sort of completed mating and needs to take care of hatchlings.

So it's like this normative change that's occurring over the transition to fatherhood.

And then there's probably a rebound, right?

And then dad maybe knocks up a new bird.

But it looks like you see kind of similar patterns in humans, rats, and primates as well.

So testosterone levels sort of fluctuate with your reproductive demands and also with your reproductive strategies.

So if you want to maximize your number of offspring, you probably want high T. But if you want to actually do a good job of parenting, you want lower T. And also, you're not as prone to create more progeny that you would have to then care for but be divided because you've just had this one.

Right.

There's like this life history theory that sort of determines when does it make sense for our hormones to change to support our different roles.

Totally.

So dad bod is a thing.

It's like this humorous... Trope.

Yeah, exactly.

But it's a real thing.

Men actually do often gain weight across the transition to fatherhood.