The standard argument is that it is the other way around -- we've settled on a 8x5 scheme _because_ our breaking point is around 40 hours. However, like others in this thread, I'm not sure I agree.
I always thought: we work 40 hours a week because we work 8 hours a day; and we work 8 hours a day because Robert Owen's mantra "Eight hours' labour, Eight hours' recreation, Eight hours' rest" caught on.
I always thought: we work 40 hours a week because we work 8 hours a day; and we work 8 hours a day because Robert Owen's mantra "Eight hours' labour, Eight hours' recreation, Eight hours' rest" caught on.