The Brown Gene has been 'purified' for centuries.
As too has the Black and Yellow Genes.
All good stock 'thoroughbreds'
The European Gene is relatively week (hence why they call it 'recessive').
When a White person has kids with Black, Brown or Yellow partners. The kids turn out looking more like the 'darker' ones, than their white parent.
That's because the Black, Yellow & Brown races haven't been 'diluted' as much.
Instead, they are like a Samurai sword ...having been 'folded' over again and again and again.
Not only that, the Black, Yellow and Brown races have had the luxury of 'greater numbers' to fall back on.
The White Race has forever grown from a very small gene pool.
Very fragile, like a white dove.
In fact, the concept of White ...real White.
Not Raven haired or Brunette or even Ranga.
But Blonde 'white'.
Is a very 'rare' thing.
Why? Because it's just a 'weak' gene pool.
If you had centuries of just 'Blondes breeding with Blondes - you might end up with a substantial looking 'white' race.
But, lets face it - the 'White Race' is really a bunch of Brunettes, Rangas and Raven haireds 'faking their blonde look'.