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i'm willing to debate that some africans and nordics, depending on the regions, are close to the "human" definition of pure, you could add asians but lets keep the bullshit simple.
Depends on what science you believe, but as far as what is commonly believed is that Asians, Europeans and everybody else outside of Africa descended from a single African group.
Nordics are not separate from Africans in terms of purity, they descended from them and through a small number of evolutionary changes, they lost and gain various characteristics. Everybody on earth is of African origin. An African man and Nordic man comes from the same stock. Regional adaptations caused the changes that made the Nordic man.
At a genetic level the changes are tiny in terms of differences, of course to humans depending on their viewpoints those changes make all the difference.