At least where I'm at, its more that most girls with multiple younger siblings or cousins have probably dealt with them under parents, aunts, etc. supervision than boys. Mommy and daughter bonding time (sometimes Grandma and Aunts).

Learned behavior reinforced with toys of the same nature. Lots of girls these days don't have that extended family or siblings to learn with.

I'm turning 30 soon, and my female friends seem to get invitations to look at someones newborn. I sure don't any of that.

Look up the male / female percentages on daycare workers and you'll get the consequences of that behavior.

The parent didn't imply "maternal instinct". That's one explanation for the gap in knowledge. The other is socialization. It's no secret that girls play "house" more, play with dolls, are taught by traditionally maternal role models, are more likely to take babysitting classes, etc.

More women than men plan a large part of their life around being a parent.

I downvoted him for expressing the factually incorrect and IMO dangerous notion that knowledge has to be inborn or learned by means of formal organized schooling. And for ignoring the obvious fact that the reason why modern women are clueless around children and men clueless around women (especially in certain circles :p) is that they spend their youth locked up with other clueless children and discouraged from expressing their gender (because equality and whatnot) instead of hanging out with experienced adults and learning from them. My $.02.

I think you misunderstood what I was trying to express. I was providing not an exhaustive list of modes of learning, but a (non-exhaustive) list of hypothetical vectors that could lead to the vast majority of one gender being expected to be inherently expert at a subject.