Forcing a requirement to think about providing a safe place to sleep results in at least some thinking about safe places to be awake in, and think about defenseless youth in general. If you have to think about finding a safe place to sleep every day, occasionally thinking about a safe place to give birth shouldn't be as challenging. Sounds convenient for long life and successful reproduction.
Also you can tell who hasn't had kids... without kids sleeping (and sleeping more than the parents) the older adults and teens in the tribe would go bonkers and be unable to accomplish anything. Best thing that ever happened to a newborn was sleeping alot so mom can get some food in her, etc. I guess as you get older you could ramp it down and maybe teens could simply stop sleeping, this is probably a secondary effect at most.
Also you can tell who hasn't had kids... without kids sleeping (and sleeping more than the parents) the older adults and teens in the tribe would go bonkers and be unable to accomplish anything. Best thing that ever happened to a newborn was sleeping alot so mom can get some food in her, etc. I guess as you get older you could ramp it down and maybe teens could simply stop sleeping, this is probably a secondary effect at most.