I suspect you meant this within the context of your own life, but historically that's almost certainly untrue. 50 years ago you likely would've had a job doing much more grueling work in less comfortable conditions. Conversely, your ex-wife would not have had an income producing job at all and after the age of 4-5 would've sent the kid outside for significant portions of the day.
My youngest is nearly 2 and can hold his own on a parking field, at a playpark, in a woodland, digging in the garden, etc.. Seems early 20th Century kids would be out there at an earlier age, certainly working class kids.