This jibes with my own pet theory for longevity. Our bodies evolved in much more demanding conditions than we have now. Wild temperature swings, strenuous work, etc. I think a lot of current diseases are caused by the systems the body developed to deal with these things that now have nothing to do, like an unloaded motor spinning out of control.
> I think a lot of current diseases are caused by the systems the body developed to deal with these things that now have nothing to do, like an unloaded motor spinning out of control.
People continue to influence their children long after they stop reproducing. Genes that help you children have more children are selected for, so something like a gene that keeps you alive long enough to care for your grandchildren seems plausible.
Children might have better likelihood of eventual reproduction if their parents are in good health as the parents raise their children during and past the parent's reproductive age. I could even imagine present and healthy grandparents having an influence on the reproductive probabilistic success/failure of their grandchildren.
Long juvenile period. A 10yo human child with living parents has a greater chance of surviving to breeding age than the same aged child with dead ones.
Also, a reproductive pair with living post reproductive (but still not decrepit) parents can breed at a higher rate as they are can delegate some childcare to them.
