Buffalo were killed off by the USA to signify the war on giants. The mound builders and tribal giants other than those were here in the states when the Europeans flowed over. That was the main causation. David and Goliath comes from a more ancient story where the line of David went to war with giants.
This continued on, the New Testament specifically says 'in those days' there were giants, because they were killed off. In other words, the Bible's mandate is a war on giants. There are no more, the genocide happened and continues. Note the 1200 era, end of the old age and beginning of the new. Charlegmagne appears the final great king, meaning the last open giant (Sauron and Charlemagne are close like Aragon is with his half brother orc he has to slay).
There were bigger buffalo. The little buffalo are gone because the big ones came out with the little ones running around in herds. The big buffalo connect to a world which the settlers cannot see because it require spiritual growth, you have to grow to become so big that you can expand into another world even though it appears just beyond a certain geographical border on a normal looking earthly spot. The giant stack of buffalo skulls pictures the US government likes to gloat about is indicating the size of the animal they removed from memory-- just like all the giants from the USA. That's what the USA is, the genocide of giants.
I will hypothesize that the Neanderthals were the original war, that some of them were very large. There probably are tribal giants in all countries, hiding out to await the new war to be over for a while? But the Neanderthals appear directly connected to the flood. Neanderthals may be revolted being slaves to mine gold for the leader on Kingu (moon, dark side).
Neanderthals probably therefore were running around being friendly with tribal Americans-- and unusual buffalo. That would be logical to the context and mentality of the genocidal USA.