I don’t believe we can say people were the same 10-20,000 years ago as they are now. Most of the races outside of Africa were in the process of becoming what they are now.
At one time, Australiods, Caucasians and East Asians were the same, from the Capoid race of Africa. The group that became Australiods went South and West, nito Sundaland and Sahal. The other two went North, but whites went West and East Asians went East.
Amerindians went more North and East. Amerindians are less specialized than the East Asians, and the East Asians would continue to evolve, while the Amerindians had both Caucasian and East Asian features, some tribes more than others. One thing that led to further East Asian development was the vast amount of them, even in paleolithic times, that led to the homogeneousness of them.
I believe the Ainu and Kenniwick man shared those same non-evolved Northern traits that were part of the original stock of those people who would later become Caucasians and East Asians.
Negroids evolved from the Capoids, but remained in Africa.
Whenever I chat up Neanderthal chicks,
my Cro-Magnon gonads keep stalling.
It’s not a bad lick how her brow is too thick,
but that New Jersey accent’s appalling.