Quote:
Originally Posted by
Redwoood 
I think one theory is that it's genetically advantageous to have a mixed-heritage partner because they may have immunity to diseases that you don't and may pass it on to your offspring.
More pragmatically, the image appears prettier, because each deficiency is cancelled by a deficiency of the opposite type; for every fat face there is a gaunt one, for every wide face, there is a narrow etc. The result being a face with no deficiencies, and therefore, an abundance of beauty. The genetic effect is remarkably similar when considering a statistically averaged pairing between races.