The grandmother hypothesis of evolution has been knocking around for a while now. It posits the theory that human development was aided by the existence of grandparents in tribal groups. Grandmothers are post-menopausal and reduce tribal stress around sexual competition. At the same time they are active in the care of infants and young children, freeing up parents for productive work. Grandmothers and Grandfathers are oracles of tribal experience and pass on skills long after they are physically capable of doing physical exertion themselves.
A new string to the grandmother hypothesis has recently emerged, and it might be called the “Poor sleeper grandparent hypothesis”. It ask the question: why do teenagers never get out of bed in the morning? It also raises a valid evolutionary advantage why old people rattle around the house at 5 in the morning.
If you live as a tribal group in the wild it’s unhealthy for the tribe if everyone is sound asleep at the same time. That represents a risk to the tribe of attack by other tribal groups, or from wild animals or natural disasters. It is healthy for the tribe if the teenagers talking around the fire at two in the morning notice that the river is in flood. It is healthy for the tribe if granddad is relieving his bladder at five in the morning and notices a pride of lions stalking the cattle pen.
It is long known that our association with Dogs, going back over 300,000 years, arose from a symbiosis. Their acute senses of smell and hearing complimented human sight. Dogs rapidly became our guard dogs. But there is no point in having a good guard dog if everyone is fast asleep. Dogs won’t assess the danger of the river rising in flood the way a human can. Sometimes the dog needs the guard human.
Any new parents recognise the value of having someone who is awake at six in the morning who can pick up the baby and stop it from crying, letting them get much needed rest. Granny being awake early is a further reinforcement of the Grandmother Hypothesis.
Link to a New Scientist article on the theory -> HERE