That is part of it, but there would also be things like high mortality during childbirth, and lack of antibiotics there at that time.

At the same time you have no car crashes or other post-industrial dangers.

But you also were much more likely to farm and hunt and do manual labor. All much more dangerous than office chair

Is that true? I thought there was evidence for setrong divisions of labour as soon as agriculture came along. That brings surplus and, with it, social stratification.

A lot more people used to farm as a percentage of the population. Even in the last century, especially in communist countries where pay was low. Small subsistence farmers were much more common. You might own a small plot, and some pigs, cows an even a horse. Or if really poor work on someone else's land. Just being around animals exposes you to many more dangers, like getting kicked or even infections from cleaning waste.