This is Origin Stories, the Leaky Foundation podcast. I'm Meredith Johnson.

For millennia, humans and horses have competed side by side in sports.

Polo, jousting, show jumping, dressage, chariot racing.

Horses are the only animal still competing with us in the Olympic Games.

But documentarian Nicole Tini wanted to do something different.

She didn't want to ride a horse.

She wanted to race a horse, herself, on foot, to test out something called the

endurance running hypothesis, how distance running made us human. If you love this story,

you can dig deeper into Nicole's podcast, Girl v. Horse, on ESPN's 30 for 30.

I've been a runner since middle school. Before that I was a scrawny, clumsy kid. Not exactly a jock or a ballerina. I could name, I couldn't catch. I didn't float across the room with elegance. But when I discovered running, I felt powerful. My body made sense to me.

Still, I didn't run my first marathon until I turned 30.

Like a lot of people, it came after a big life of people, a breakup.

I'd moved to cities, came out as queer, and I was trying to make sense of who I was again.

It was tough, but I couldn't believe how well I did.

I was hooked. I joined a running club and spent all my weekends doing long runs and chasing finish lines with friends.

It wasn't just a hobby.

It felt really natural.

It felt innate.

But I didn't really understand why until about two years later.

I'd been diagnosed with epilepsy and suddenly my body had felt like a stranger.

Around then, I read the book that everybody had been talking about.

Born to run.

...