Could horses ride humans the same way that humans ride horses?

In a world where horses (or any other species for that matter) were the dominant species instead of humans, could they ride humans in the same way that humans ride horses in this world? Could the human bear the weight of the horse? How would the horse sit? And is there example in real life of creatures (except humans) using other animals as modes of transport>

• Also your question is really broad, you should limit yourself to either one specific animal e.g. horses as in the title of your question; OR you rewrite the whole thing and look into how much a human possibly can continuously carry on their backs – dot_Sp0T Sep 25 '16 at 15:41
• Have you ever seen a horse in real life??? – Vincent Sep 25 '16 at 16:54
• An European horse or an African horse? – SJuan76 Sep 25 '16 at 22:40

Short answer: No (at least not if horse-world-humans are the same as earth-humans)

Longer answer: Still no
Adult horses weigh some ~1900-2200lbs. A human can apparently deadlift some 455kg (some 1000lbs). As I didn't find a number for carrying stuff on ones back, I multiply the deadlift by 1.5, which results in some 1500lbs if we're generous -> This is still nowhere near the weight of a horse..

How would the horse sit?

(a) That is the first problem - before even worrying about whether it is possible to lift a horse. Most people down on all fours won't even reach up to the lower parts of a horse. A very high saddle would be required and the higher, the more unstable.

(b) There is the ancient myth of milo of croton who, by starting as youth carrying a small heifer was eventually able to carry a full grown bull on his shoulders.

And is there example in real life of creatures (except humans) using other animals as modes of transport?

Yes, see the following video. (click link, not picture)

https://youtu.be/tkwAbzNCXK4?t=11