The donkey likely can run faster at first, but it will need to stop to rest way sooner than the human.
It's the same reason a human will always win against an equine in a long distance race: If the equine does not stop to rest, it will die for lack of oxygen.
Humans have evolved in such a way that we can fully breathe while running. Thus, we can hunt large game till they need to stop in order to fully breathe again, and then BAM!
On average, a healthy and well-trained horse can run about 2 to 2.5 miles at full speed without halting. Still, this top-speed sprint isn’t typically sustained unless under racing circumstances. Remarkably, some horses, when prepared for endurance, have demonstrated the capacity to cover distances up to 20-25 miles without stopping, though at a slower pace like a trot or canter.
An average horse can reach a top speed of about 25-30 miles per hour.
No human is running that far or fast in any race. And sure a human ( a small percentage of humans at that) can go farther than 25 miles without stopping, but by the time you catch up to where the horse stopped, it would have had time to eat, drink, rest AND leave before the human got there
I get what you're saying, but your 'average Joe' is no runner these days... I try not to be too judgemental (despite it being my super power!), but I get the impression that guys only good for a few hundred metres
Now, the donkey is probably no athlete either, but my money is squarely on the animal here...
You're correct in principal, but in practise you're laughably wrong. We've (d)evolved from hunter gatherers since the industrial (or iron/tool?) age, and fitness lost out big time