I think that you are right about what 'women's work' was, and still is, to some extent. Also, what she could do while heavily pregnant (and frequently *also* chasing toddlers, LOL!). Men and women are biologically different, and have different functions within the family structure because of those biological differences, not because of 'patriarchal oppression.' Frankly, it would be oppression to expect a heavily pregnant woman with toddlers hanging on her skirts to go out and plow the fields and cut and haul firewood, among other chores requiring great physical strength. Not that women haven't done those things, in those circumstances, when it was necessary, but that in a properly functioning intact family, it shouldn't be necessary.

As for when little boys transitioned from learning from their mothers to learning from their fathers, I suspect that had a lot to do with how patient their fathers were. Some men (and women, for that matter) are more patient with little beginners and can start earlier. And it would depend on what kind of work was happening that day, too. Milking the gentle old cow, yes. Planting large seeds (peas, beans, corn) in the garden, yes. Falling trees, probably not.