Fleas and lice live almost exclusively on the hairy portions of our bodies if we are so unfortunate as to be infected, and to a minor extent in our clothing which is basically nothing more than synthetic fur.
The loss of our fur has truly contributed greatly to our managing our problems with parasites by minimizing their habitat.
We are indeed great long distance runners and in hot weather a band of men working together can run a horse to down and catch it because while a horse can easily leave one man in the dust three or four are spread out properly can overheat a horse in hot weather to the point it actually collapses covered with lather.
I helped a couple of other guys back in my younger days catch a horse determined not to be caught in a large pasture. Just one guy would probably never get close enough to a wild horse to kill it but I could have easily stabbed the one I helped chase down with a spear with no need to throw it once it was standing exhausted with it’s head hanging down and all lathered up.
(Just in case the horse lovers are upset–this was a horse that was never trained or handled since it was a colt and it had to go because the property owner died.
I am afraid it most likely wound up as pet food but it at least left the premises alive in accord with the wishes of the family.)
If it had been up to me I would have euthanized it with a deer rifle and buried it.That would have been much safer and much easier and quicker as well given that a tractor with a loader attachment was handy.
Veternarians are lot more expensive than bullets and farmers usually stomp their own snakes meaning we do our own necessary tough chores whenever we can.
Now I know horses weren’t one of the animals we hunted in our early days on the savannas of Africa after we came down out of the trees but it does seem very likely that our bare skins enabled us to chase down prey animals that were adapted to running only far enough to escape predators also hampered by a fur coat.
But there is another and even better possible reason we lost our fur. Any part of the body of an animal must contribute more to its survival that it costs in energy and once we were living on the more or less permanently warm to hot savanna and using weapons we didn’t need the fur any more and so we could gradually lose in profitably in the process of our evolution.
Less fur means more energy for stronger arms and legs and lungs etc.
No other species uses weapons like we do and thick fur covered hide is effective armor for both predator and prey. This is probably an adequate explanation for lions and zebras for instance retaining their fur in a perpetually hot environment.
Are these proven ideas?
No, but otoh neither are they disproven.