A friend died recently. She was ninety-eight years old. I
was never to try to call her before noon.
She explained that she only could sleep in the morning, that
she was awake through the night – while I was sleeping. This happens with older people. We tend to go
to bed and rise earlier than the rest of you. For many of us the night brings
only fitful sleep, a period of wakefulness. We replenish what remain of our
brain cells, or whatever it is sleep does for us, by napping during the day.
Why is it this way? It just might be evolution, something
written in our genes to promote survival of our – village.
Scientists recently reported (Proceedings of the Royal
Society B and reported in the New York Times) results of a study of sleep
patterns of an east African hunter-gatherer people, the Hadza. The Hadza
sleeping environment may have similarities to that of earlier humans,
researchers said. They sleep outdoors or in grass huts in groups of 20 to 30
people without artificially regulating temperature or light. These conditions
provide a suitable window to study the evolutionary aspects of sleep. In their
study they found that somebody was always awake. During the period of the study everybody was sleeping for only an average of 18 minutes in a twenty-four hour day. During the night and in
the wee hours of the morning it was the grandparents who tended to be awake.
And watchful.
The scientists hypothesized that the young folks needed
their sleep more than the grandparents. This
is because the young folks were the ones who needed light for their
work, whether it was gardening, hunting, or caring for the family and protecting
against predators and other intruders. The grandparents were tasked with the
job of watching through the night. Keeping an eye out for encroaching threats to the village.
So, I thank my friend for her sleeplessness. I am quite sure that her inability to sleep during many nights over many years provided our small village an important
degree of safety.
Is it my turn?
