The model of men work while women watch the kids was most of history. Of course is completely ignors 'womens work' which was very needed for survival and defined by things you could do while also watching kids. for the first few years kids eat from mom so she cannot get far from them (after that she is probably pregnaunt again thus restarting the cycle). Mens work was anything that needed to be done that could not be done when pregaunt or nursing a kid.

today men have the ability to watch kids thanks to formula (though it is better for the kids to eat from mom - this is rarely talked about because it is easy to go too far and starve a baby to death in the exceptions).