I've already made a couple of comments but I thought I'd throw this one in too, ancient societies held coming of age as a big deal because it meant that you'd reached a point where you were worth investing in, prior to that you were cannon fodder.

You didn't have to make it to adulthood, if you made it to five you would likely see fifty on average. Edit, apologies that it still leaves an average. Second edit, it's also theorised that children don't like the taste of vegetables until they reach puberty, children are predisposed not to eat plant matter as they are incapable of knowing whether or not it will kill them.

I think half of child mortality rates are simply from babies being fucking suicidal.