>>12034699Hybrid vigor is because hybridization masks recessive genetic defects.
recessive genetic defect do disappear because they are defects, but they do so slowly since they are recessive. So if you breed with someone closely related (recent common ancestor) you might both carry the recessive gene and have the defect expressed. But if you breed with a distantly related human (distant common ancestor) such as a person from a whole different continent, then its is very unlikely that recessive defects that existed back when you had a common ancestor ( a genetic defect that you share) will be present, and so it is very unlikely that you will have matching recessive defective alleles and you child will have no defective recessive genes.
What about dominant defective genes? Well the parent would have the defective phenotype and hybridization would only help if the alleles of the other parent are healthy AND relatively dominant. This is possible because an allele that is dominant compared to the other alleles in that population might be recessive relative to some alleles present in a different population.
So yes mixed people are stronger, however this is not a quality they can transmit, hybrid vigor is mainly in the first generation, for statistical reasons [hand waving here].
The reasons miscegenation might not be good are varied. For one, it kills diversity. Different separate groups that evolve to be different have qualities that may get erased by other qualities of different people.
Simply put, if you think that being tall is better, then mixing with short or strong people might give your children extra strength but they lose their edge you had by being tall, and they are still not strong enough to have an edge there.
Finally people are naturally solidary with more closely related people so mixing undoes the glue of society. Like a woman with her kids versus a chick running a daycare, which is more nurturing?
