Genes don't disappear by being dispersed. Genes disappear in populations which encourage some sort of long term inbreeding. If a person has a pair of matching genes, say from multi generation cousin marriages, then their is a gene that has gone missing.

6 billion people with 23 gene pairs... I think it would be very difficult to form one set of a limited gene pair from hybidisation. Essentially to have one set come out of that is like stirring a latte and have it separate into sugar, milk, and an espresso shot. Genes don't disappear when shared by mixing.

I'm Celtic-Scandinavian one brother is blue eyed blonde, the other has hazel eyes and metallic red hair until it went auburn then went. I'm more dark hazel eyed, brown haired and going going gone. The mix of genes has caused quite a variation not hybrid sameness.