Peter Attia, M.D.

I remember my overly simplistic, and this is almost 30 years ago, but I could have sworn I used to think about this in the embryology class as by default, we are female, and this gene had to turn on to basically take the XYs and make them male phenotypically, but that's obviously oversimplified.

Because if you have an XY that is missing that region, you will be phenotypically female, but chromosomally male.

Correct, you won't be able to reproduce, but for all intents and purposes, you would look female, correct?

Oh my God.

I have not heard that term since medical school.

What a blast from the past.

And they're high.

I remember they're almost in the chest.

That's a whole other... Maybe temperature regulation?

I'm just going to take you down a stupid detour for your next book.

We were at my younger son's baseball party at the end of the season.

So now picture at the time, a bunch of 27 year old boys running around the pool, playing baseball, playing football, goofing off.

Me and the dads were sitting there hanging out and we were observing their behavior.

And I came up with this observation, which is

There's estimated to be about 110 billion humans that have lived over the past 250,000 years, inclusive of, of course, the eight or so billion that are alive today.

And just watching this small group of 20, you could already see the number of times one boy would walk up to the other and sort of flick him in the nuts.

Okay.

And I was like, all right, to the dads.

How many times in the history of 250,000 years has one male gone up to another male to flick him in the nuts?

What's that number?