I would, too, like to see some hard data on your hypothesis, although I believe that there are too many inseparable human and enviromental variables at play her

I would, too, like to see some hard data on your hypothesis, although I believe that there are too many inseparable human and enviromental variables at play here. At the end, the change in role and power is a very human development (see also: families, partnerships, child-parent relationships).