Alien Grays

What if Man was brought from this planet to another one a lot like earth. The only difference was time went by just a little faster let's say for each year here 2 or 5 years went by there. Now mankind has a way of surviving and women without modern day healthcare die, a lot. But, women have something that keeps making them stronger. Womens X chromosome can pick between the mom and dad picking the best of them. This over time makes them a stronger sex. While the man only takes the dads Y as a fixed. This if it becomes broken is not repairable. Again young humans to survive women are born 3 women to 1 man. So as medical science becomes better there ends up being more and more women on the planet and less and less man. Now if humans try manipulating DNA they could lose the entire male population altogether. After that happens no need for breasts and cloning takes place. Now you start making a copy of a copy https://www.youtube.com/watch?v=S90VPU62_FM

Now with your superior group dying because first of no sex to create immunities. No new DNA. But, you find out there is another planet of humans, all flawed and dizzied, planet full of toxins they can live through and Men.

While, now you can start to build yourself a hybrid race that can have children and your kind will live on again.