Except that with humans, with our super-helpless offspring, still gestating even after they're born, the bonds between humans and the social connections around the raising of infants are particularly important. So, for example, having grandparents around can help survival rates, even if those grandparents are no longer fertile themselves. (Some argue _especially_ if they're no longer fertile, as childbirth becomes more dangerous with age. Most species other than humans have no menopause, just a gradual fertility decline.) Another example, there is some evidence that attended human births are more successful than unattended births, even if the attendant doesn't have experience or skill.
Jenny Brown