Keeping fit permits a longer lifespan, which can be important for the evolutionary fitness of grand kids. Also, I'm being a bit facetious, I don't believe all o

Keeping fit permits a longer lifespan, which can be important for the evolutionary fitness of grand kids. Also, I'm being a bit facetious, I don't believe all our behavior neatly fits into evolutionary motivations, and the science doesn't claim such rigidity. It does, however, have startling explanatory power about a bunch of things we do. I'd suggest watching the lecture series in the sibling thread