So now we're including "survival of the unfittest" as part of evolutionary theory? Sorry, this makes zero sense. If humans really did evolve, then we hit the lottery - several times.
Fitness doesn’t mean what you think it means. As others have noted on this post, this mutation confers some resistance to malaria.
When the options are “malaria with high probability from birth onwards” or “heart attack after multiple decades with high probability if nothing else kills you first”, this is fitness.
Besides which, if humans didn’t evolve, you need to explain why the creator didn’t use a better mechanism to prevent us from getting malaria. For example: not creating malaria when they created us.
