Because longevity isn't essential to our survival. You're suggesting that diverting energy away from other traits in favour of longevity would have no negative

Because longevity isn't essential to our survival. You're suggesting that diverting energy away from other traits in favour of longevity would have no negative impact. IMO there are all sorts of possible negative side effects that might emerge. Like a longer life making us more cautious, individualistic, and short sighted (not personally but on a species scale). You could argue this is already happening due to environmental comforts and medical advances. In fact dramatically tweaking a trait like longevity for a new generation would likely have a massive impact on their personality and culture... talk about a generation gap.