This will be a controversial topic, but one that hasn't been willingly discussed in genetic/historical inner circles.
There is no denial that most Asians descend from mainly 3-4 genetic Haplotype markers:
1) East Asians and Southeast Asians mainly have the Haplogroup O marker
2) Uralic and many Siberian/Central Asians have the Haplgroup N marker
3) American Indians and many Siberian/Central Asians have the Haplogroup Q marker
4) OK, finally Indo-Europeans and some Central Asians mainly have the Haplogroup R marker
Indo-Europeans may have started out Mongoloid but ended up Caucasoid by expanding west into Europe/India and absorbing the earlier natives (who were either Middle Eastern farmers or Neanderthals). As they expanded more, they became more and more Caucasoid.