More like the older people would probably be less likely to be out hunting elk or whatever physical activities and more likely to be watching the children. I doubt it would have been codified or anything.
I still don't understand the distinction you are making. At first I thought that you meant that literally a generation would not procreate. But now I think you are trying to say that young adults would not be doing child rearing. Are you suggesting that mothers would return to physical labor right after birth to defer child rearing to elders, or after breast-feeding? That mothers would somehow not be present as much as elders?
Correct - child bearing obviously continues as normal, but child rearing is delegated to the grandparents. This seems like an advantageous setup in both a pre-modern and post-modern context, where there’s significant value placed on women performing labor during the age of lowest-difficulty child-bearing.
