First of all, modern medicine is not available to every human being.
Well sometime in the future it will be,
There are also uncurable diseases such as HIV which is actively selecting for CCR-5 mutants. Another way of stating it is that there will always be selective pressures on the human population, it is just a question of which ones.
So what kind of mutation would makeyou have more then 1.9 kids compared to your neighburs 1.9 kids?
I think the larger question is if we will ever take direct control of our own genomes.
As long as there are creos and other fanaticsout there it will be very hard to impliment, sayascan that will test your childs genome while it is still in the womb and treatment for all his will be genetic faults while it is still possible.
For the Iceman, he has trained extensively to withstand these temps. Also, post-natal development can have very large effects on brain function. There is a very large question of how much is due to DNA and how much is due to environment.
I doubt if you train your whole life you would be able to be submerged in ice for 2 hrs.
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