> is rather telling evidence that our forebears
  > found it to be the most effective way to bring
  > children in line

Our forebears also felt that the best was to run a society included things like:

- Slavery / Indentured Service as a means of generating wealth.

- Punishing women for sexuality (because all women were temptresses, and a man couldn't be blamed for infidelity, rape, etc).

- Torture against criminals / political prisoners.

- Religious wars.

I don't think that "our forebears did it, so there must be something to it," is a generally effective argument.