If you make note of the differences in physiology between the male and female body, you might discover that there is a non-arbitrary reason why industries requiring childcare have traditionally been the domain of women.

You might discover that we no longer heavily relying on human labor or do you sugest that women are incapable of operating machines?

If a particular woman, regardless of her physiology, can pass the physical bar necessary to be a firefighter, why in the world should she not work in this domain?

As a man, my out-of-shape physiology precludes me from being one - that doesn't mean that my gender should be excluded from it.

This is correct and I agree with it, but my statement goes a step further. I am saying that women should be strongly encouraged to be part of these occupations, in the same way that men are strongly encouraged to take paternity leave and help with child rearing.

And before the invention of power tools you'd have had a valid point.