That's actually incorrect, the average life expectancy of people before modern medicine was low because of the high amount of infant mortality (bringing down the average). But if you survived childhood, you could easily live into your 50s, 60s even 70s for some.Its's obviously way more common today but it wasn't unheard of in the past. 

 Yeah, you're probably right, but we can't know the exact number of people who died from skin cancer in the 1800s. 

 Yeah that's true. Though we can probably get a ballpark figure based on doctor journals describing skin cancer lesions on patients and extrapolate. It's not accurate but the best we can get.