I'm sure there are longevity gains that can be attained with embryo selection or direct embryo genetic editing. Might even be some low-hanging fruit there. But

I'm sure there are longevity gains that can be attained with embryo selection or direct embryo genetic editing. Might even be some low-hanging fruit there. But I see no reason to believe this to be the only possible source of longevity gains. Sure, the evolution may oppose longevity, but evolution can go eat shit and die. It still works on humans, but it works too slowly to be able to do too much - we can't rely on it to fix our problems, but it also wouldn't put up this much of a fight if we fixed our problems on our own.