Why is cancer prevalent nowadays?

There's a lot of cancer, at the present time, for a number of reasons. We do have an increasing amount of carcinogenic substances in our environment. Atmospheric nuclear testing in the 1950's and early 1960's has created a lot of nuclear fallout. Various chemical industries and products have released carcinogens into the environment. We once used Agent Orange, containing the intensely carcinogenic compound dioxin, as a herbicide. In addition, the average life expectancy has increased, and the longer you live, the more likely it becomes that you will eventually develop cancer. And medical testing is better. Many cases of cancer just were not diagnosed, in earlier historical periods, and people would instead be said to have died of some kind of fever, ague, etc.