What assumptions are you basing this on, curious to know if horses have a disadvantage over longer durations.

I would recommend reading _Born to Run_ by Christopher McDougall. Later in the book he addresses this very topic and expands much more upon the topic of humans and long-distance running.

Humans sweat, which most (all?) other animals don't. In that way we can dissipate heat through our breath, like other animals, _and_ via perspiration, meaning it takes us much longer to overheat.

Additionally, humans stand upright, allowing us to disconnect our stride from our oxygen intake. Other animals' strides correlate (mostly?) 1:1 with the breaths they take. So when a cheetah outstretches in its stride it breathes in and when its legs come together it exhales. Humans stand upright, meaning we can breathe however we want regardless of our stride and speed. We can take deeper breaths because we don't have to exhale every time we stretch our legs.

Humans are the ultimate marathon runners, even more so than horses, evinced by the fact that there are some people throughout history who have run hundreds of miles in the course of days or weeks. There's a theory touched upon in the book about how this allowed us to dominate the animal kingdom before we even had tools. Humans could relentlessly hunt and exhaust animals as long as they could keep them in sight or otherwise keep up with their tracks.

I'm not doing the book or the topic justice, surely, but if you're interested I highly recommend the book.

Horses are part of a not that long list of mammals that do sweat almost all over their body. That is indeed one of the reasons why they are competitive with humans at running long distances.

Not sure about horses specifically, but humans are uniquely adapted to long distance travel among large land animals and used it for hunting by out-performing most other species:

https://en.wikipedia.org/wiki/Persistence_hunting

Edit: it's one of two things I know of that we really excel at besides thinking. The other being accurate throwing, which perhaps explains baseball's enduring appeal:

https://what-if.xkcd.com/44/

To note: horses compete alongside humans... while carrying a human.

Very cool. I'd like to see a horse vs human ultramarathon, more like the 24 hour time the parent suggested. I was surprised human and horse competitors were so close at that distance!

tl;dr: Annual 22-mile race with both pedestrian and equestrian competitors. Out of the 40 times it's been held, the winner was a human twice, and a horse 38 times. Typically the spread between the fastest human and the fastest horse has been less than 10 minutes.

Probably related to https://en.wikipedia.org/wiki/Endurance_running_hypothesis

My assumption when I read your parent comment was: Two legs are more efficient than four, and can go farther before exhaustion... but that's full of holes. Horses are huge, bristling with energy, right?

Having the weight centered vertically above the legs and a smaller weight is more energy efficient

It's true, google it. The combination of two legs and relative lack of hair make humans one of the best long distance runners in the animal kingdom.

Literally speaking, I don't know what is not true about my statement above.

But your point is well taken; it is also applicable to this article as well: maybe Go is not the game people can beat machines, but StarCraft 6 could be. Or maybe I can fold my laundry more efficiently than any machine available.

*sometimes