[cmrdporcupine]

I gave you the reason right there above, but you cared not to read it: longer breastfeeding period.

Plus the fact that in a hunter-gatherer society people choose not too have too many children for the same reason people make that choice in advanced capitalist economies. Children become a resource burden.

In an agrarian economy, your children are extra hands for farm work. In a hunter gatherer society they are mouths to feed in an environment with intrinsically limited resources.