I thought they were rising?
Life expectations that we read about are based purely on high city society. Around the world, the cancer and disease rate is actually raising dramatically, we just don't get that coverage.
Also there's been a sharp spike in the concentration of carcinogen exposure all around the world since the 50s. A lot of people who were born back then are dying from related diseases and such. Just saying a lot of us who don't die to forceful causes will probably die of cancer or genetic diseases
There's a large pool of weak genetics that a lot of us don't get to pass down or don't experience because we die to other causes like car crashes or circumstantial bullstuff. Good example, my family has genetic cancer, and all of my mother's aunts and uncles have all died of cancer, lung, liver, or otherwise. Most of my friends have certain deadly genetic diseases, most of which are actually induced by gene altering chemicals found in the environment.
It's scary the more you think about it.
