>>14364132A lot of anatomically modern human genes on the non-African branch are not present outside of Eurasians (ex. BNC2, MC1R, OAS1/2/3 and TLR1/6/10 and countless other examples of which the most important for you are probably the 13 EEMH that exhibits longer average frontal lobe length and taller occipital lobe height closely linked to increased intelligence, for further reading see [1]). Because there are not even alleles to bind with these genes often become tightly bound to histones and effectively become inactivated intragenes. You also have other related effects such as such as Epistatis due to the genes being on different locations on the chromosomes. That is why many "white" and "asian" babies mixed with African mostly look African. What shows up in the phenotype has a well understand molecular mechanism.
People who still think genetics are as simple as 50:50 are midwits who have not understood a paper published past Mendel's study. Mendelian inheritance firstly applies only to organisms with allele variants of the same genes in the same position on both chromosomes, and secondly there are various othe mechanism for dominance and recessivity. Especially when you have chromosomes of different loci for the genes none of those things apply, you get a mess of a mixture on a molecular level. You also can't "breed genes in or out" using retarded eugenics ideas.
1. Balzeau, A.; Grimaud-Hervé, D.; Detroit, F.; Holloway, R. L. (2013). "First description of the Cro-Magnon 1 endocast and study of brain variation and evolution in anatomically modern Homo sapiens". Bulletins et Mémoires de la Société d anthropologie de Paris. 25 (1–2): 11–12.
