I think our bodies evolved very well for a species that lived to ~ 40 years of age.
1) Born.
2) If you survive the childhood diseases, etc., you've got it made!
3) Hormones kick in. WooHoo! Fun times!
4) You have your children at 18-22 years old.
5) Raise kids, impress rivals with strength and cunning.
6) Kids start to grow up, help with chores, help protect the homestead.
7) Kid notices unattached beauty down the road. They get hitched.
8) Kids turn 18, just in time for them to take over running the homestead.
9) You enjoy your golden year or two, wander off into the woods, and get eaten by a bear.
10) The end.
If doesn't make sense for kids to have hormones running at 11 for a few years, have to wait a few more years to be able to start their adult life and to be able to support their offspring, then live another 50-70 years. We should have shorter life expectancies or the mating instinct should come later. But as it is, [link|http://pediatrics.aappublications.org/cgi/content/full/108/2/347|girls are maturing earlier] than they were years ago. Things are heading the wrong way on both ends.
We're going to have to start fighting (or changing) our biology on a major scale, or society is going to have to change in major ways, because otherwise there are going to be too many children raising children.
The missus and I have always felt that we didn't want children. There is the little issue about what we'll do in our "golden years".... I've joked with her that we can adopt some 17 year old kids when we're ready to retire.
"Hey missy and sonny, take care of us and you'll get a nice reward!"
:-/
Cheers,
Scott.