On the subject of life expectancy in the past, it is a common misconception that everybody died at the age of about 30. I read a book some time ago which dealt with life expectancy among villagers in early modern Britain (16th, 17th and 18th centuries), and, as far as I can remember, the average age of death was about 30, but this of course was dragged down by high rates of infant mortality. THose who survived into adulthood generally lived to about 40 or 50, and some, I think possibly about 5-10% of the population, made it into old age - it was not unknown for people to reach ages of 100. Essentially, life expectancy was far more random back then, in that those who escaped disease lived as long as moderns do, essentially until their bodies wore out. Nowadays, thanks to medical science, everybody is able to live that long.
Also, I think that it's important to remember that, before the advent of modern medicine, it was probably difficult to identify exactly what disease somebody was suffering from, therefore, most people who died of cancer before the industrial revolution may have died of other diseases.