About 30 years ago, when I was a kid. I was lucky enough to grow up in the country at a time when it was considered OK to allow small kids to roam about in woods all day alone.
Of course back then nobody called it "Bushcraft", the only kit I had were the clothes I stood up in and a couple of knives but messing about in woods, rivers and hills as a kid laid the groundwork - shelter building (or "camps" as we called them), watching birds and wildlife, ID'ing trees and plants, building tarzan swings, shooting black-widow catapults at "No Fishing" signs...