Emperor Caesar is right Miss Nicole.
The greater the genetic variation - the healthier and more robust the immune system and less likely to be prone to mutations that can scuttle a person's well being.
Also intelligence - as 'cultural' aloofness comes easy and much more.
The concept of 'pure breeding' with humans is actually an act of fragility. Just look at the isolated rural towns and villages of Australia where after just 100 years - deafness, blindness and other abnormalities begin to show.
Libya - a closed nation, where a man can travel to the other side of his nation and still marry/breed with a distant relation.
China - a huge population, but a very 'thin' gene pool also shows where the problems arise and ask any Geneticist and they will tell you that the Chinese gene rates 'low' on the score-card.
The San Bushman has the highest rating. But these people have been around for so long, they still inherit the ancient genes that have long since been lost to other peoples.
Before the
'Purple'
Gays ripped off the 'Rainbow' emblem - it belonged to the 'Coloureds, Mongrels & Mixed-Race' peoples.
The success of the Homo-Sapiens over the other Hominid peoples and Neanderthals, Denisovians (& the isolated African Branch) - was due mostly to their 'mixed-genetic' versatility.
As Caesar stated - they also have 'cultural' versatility too, and if you look back at many cultures - the ones that don't become isolated 'pure', kick on to become great Cultures.
So the 'Royal' Families etc - and their 'Pure' breeding is really a 'weakest link' of Line.
This is why Humans are different to Animals.
Animals restrict their versatility and variation by usually just having 'one dominant' male.
25 female genes for variation
1 male gene for variation.
...kinda lopsided isn't it.
Genetic variation is like Cultural versatility.
That is the real success that takes Humanity into the future.
Who knows? Maybe 'mixed race' relationships succeed where homosexuality fails?