Some childcare is being done by grandparents because people are outliving their reproductive capacities. It's part of the evolving nature of society.

A major mistake has been made evolution wise--children are becoming sexual at younger ages and yet society says NO! thou wilt not before you're married. Instead of our puritanical bias, we should have been educating the young people all along in their sexual natures, how procreation happens and letting them do it when they want but with sufficient protection to keep unwanted pregnancies at bay. Then, when the child becomes an adult and is ready to procreate, they are drawn to and hopefully mate for life with a suitable specimen.

Instead, we have screwed (no pun intended--oh, heck maybe a little intended) with nature through our society's puritan morality. The Puritans should have drowned on their way over here.

The point is, we are still evolving. The current patterns will lead to some kind of evolutionary future that would be interesting to think out and explore. Asimov did some of this in his four novels about the future beginning in Caves of Steel and then carrying it on in The Naked Sun, The Robots of Dawn, and Robots and Empire. It would be interesting to reread those novels to see if there is an iota of truth in them relating to possible futures extrapolated from the roots of today.

The family disintegrates, the work family replaces that to a degree. We flock together based on career choices. When a mating occurs outside that parameter, I wonder if it the chances of permanency increase or decrease.

A large number of family units are mother and child or children with a more distant father who mates and creates more children with another woman. The woman may mate again and have more children with a different father although the first (father with multiple wives) is probably more probable than the woman with multiples.

Women work and hit a glass ceiling while the males sometimes run from their child support responsibilities, laying it all on the woman. Perhaps the Mormons had it right? A male had to be able to take care of multiple wives and children. Families were permanent. The woman was monogamous, the men not. But there were rigid rules.

OTOH, women can have multiple partners, too, but can only get pregnant one baby at a time. Our instinct is to find a provider so we push repress our desire for multiple partners in order to focus on the provider.

But then you throw into the mix the fact that our Earth is getting rapidly overcrowded and evolution will take that into account. Realizing this, we are limiting our families in this country (and some others, i.e. China) to fewer children than we did around the turn of the previous century (1900).

So how does multiple partners figure into this? The American males may be having the same # of children spread among more women but the women themselves have smaller families. So the child population is spread out among more women. Overall, we are evolving into a society that has fewer permanent marriages so more partners, but overall fewer children.

There may be a lot of holes in the above since it is off the top of my head interrupted by cats insisting it was their dinnertime. Feel free to pick away. It's a fascinating subject.