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Thanks for Your Mind reply to my Question. But on My Which Authority Do You Claim "The World is Overpopulated"?

I as well Emphasised that" what would Happen To Mankind if ALL HUMANS BECOMES GAY/LESBIAN BY LEGISLATION"

wel the other person answering picked it up the same way I picked it up. I read it the way " What would happen if gay marriage was legaised all over the world. It is highly unlikely that everyone would turn gay. Read Dan Brown's book " inferno" . Even though the story is fiction , the basis of the book is fact. The world is overpopulating.

Thanks ! But My Question is about GAY/ LESBIANS; Not Heterogeneous Sexual Relationship.

What Will happen to Human Race if it is Legislated That Men Marry Men and Women Mary Women as it is already Happening In Some Part of the World??

That is covered by the first part of my answer.
More marriages will be issued, wedding bakeries and planning companies will make a bunch of money.

What else would happen?
Same sex coulpes already exist and live together in the world, whether you make it legal or not.