Interesting point about the Sa’ami and Indo-Europeans.
I read an interesting thing that attempted to ‘reconstruct’ Indo-European culture from the words in common from Ireland to India (minor exceptions aside). Lots of words for sheep, horses, and the parts to a chariot (axle, wheel, etc); thus they surmised that they most likely rode horses, herded sheep, and had chariots.
Consequently they'd hook up a couple of horses to a chariot and you could pull two men in battle ~ although those same two men would be too big for the horses to ride, and would wear out quickly.
Later, through adroit use of animal husbandry (eat the small ones, breed the big ones) horses got big enough to ride.
During the early stages of horse culture guys on chariots rode back and forth from China to Central Europe on chariots ~ various improvements were invented all along the way. They have literally dug up some of the very first axle rigs ever manufactured ! This stuff is that new ~ it's not Ice Age work.
The Greeks, Romans, Persians, Egyptians and Chinese would have been astounded at the big Belgian horses developed for the carriage of armored knights! Those guys are about as big as the elephants in use in Hannibal's time.
Indo Europeans "received the horse" from others ~ but I think they put them to use faster and more effectively than any other group. Hence the successful spread of their language(s).
“Lots of words for sheep, horses, and the parts to a chariot (axle, wheel, etc); thus they surmised that they most likely rode horses, herded sheep, and had chariots.”
That makes sense, since the Indo-Europeans spread out from the area around the Middle East, where chariots were common and very important technology. Nomadic herders would be a likely lifestyle for them, considering how far they ranged.