It is much easier to murder than settle differences peacefully.
There is also the issue of wanting power, if some can wipe out a group of people easily, then other races/creeds/nationalities will likely fall into line sooner than later. Hitler and Stalin did this prior, during, and post WW2.
No we haven’t because look at the world we’re living in right now. All these protest, racial discrimination.
The answer is the Bering Strait land bridge.
