Ever wonder why humans, who have predominantly lived and worked outdoors until the last century, suddenly need suncream to go outdoors?

Ancient texts don't talk of terrible sunburn, everyone having skin cancer, or anything like that.

My guess is the main cause is ozone depletion: https://www.nasa.gov/images/content/433982main_percent-chang...

UV-b has increased substantially since 1979, and considering CFC gasses were first used in the 1930's, it's likley that UV-b has very significantly increased since then.