The really odd thing is why? Mankind had a good thing going for him, a soft life. A little hunting, fishing, and herding, the old lady working the garden. Then Bang moving tons of dirt and rocks, living by the sweat of ones brow, makes no sense.
It was the rise in political order, and corresponds to what was going on elsewhere at about the same time. It was still homegrown, but short of psychic activity or a big huge coincidence, the only way for that to happen just like that is the existence of seafaring and seagoing trade. The various cultures witnessed each other’s activities and borrowed ideas here and there.