>Humans live comparatively long because it takes a long time for individuals to acquire the skills we use as a survival strategy Species need to live until rep

>Humans live comparatively long because it takes a long time for individuals to acquire the skills we use as a survival strategy Species need to live until reproduce, maybe several times, and see the next generation into being able to live on their own. That is about 35-50 for humans (granted the 15-20/generation - relatively prolonged maturation period given our size - is primarily because of the brain/skills development you mentioned). Additionally, because of the complexity of societal organization, skills and other knowledge, we've got boost from having the grand generation around to help and transfer knowledge and experience. That brought us to 60-70.