Is a one world country flawed, for human biodiversity and checks and balances in trade?

i just dont think it could work because green cards and visas help to make it fair but help preserve a rate of mixing of diversity among the ALL the different peoples, but so people who chose to stay in the country of origin are now on a slightly seperate evolutionary path, but the controlled flow allows the best combination of importation and sharing of diversity over time so we dont all get really sick with hereditary disorders by overlapping so much we become no more than like 4th or 5th cousins. And on rly the pure chance people claimed land with resources give a lot of checks since most stuff can be found in a couple places. saudi arabia doesnt have most of the worlds oil, most is untouchable by people as of yet in like Antarctica and alaska. and i guess a catalyst for technological improvement to out supply the other.