Humans are meant to keep active as we age, according to the “active grandparent” hypothesis put forth by evolutionary researchers . We have a significantly longer lifespan than our close cousins the chimpanzees, who also happen to be considerably more sedentary. One of the study authors, Dr. Daniel Lieberman, observing chimpanzees in the wild was surprised by how much of their day is spent “sitting on their butts, digesting”. Hunter gatherers, in contrast, typically spend about 135 minutes of moderate to vigorous physical activity a day, even when they get older.
The first reasoning I heard for an evolutionary advantage for this behavior was “the grandmother hypothesis” promoted by anthropologist Dr. Kristen Hawkes. She observed hard-working older Hadza women in Tanzania helping to gather tubers, which can require going several feet underground with a digging stick. Women with infants to care for can’t spend their full time gathering food, so the Grandmas pitch in both with the child caring, food gathering, and other chores. It is fitting to make note of this today on mother’s day.
Dr. Lieberman and colleagues hypothesize that similar contributions are made by grandpas, so there is an evolutionary advantage for both men and women to stay active long past their reproductive years. The common thing that we need to take it easy as we age (time for our rocking chairs) is a myth: according to Dr. Lieberman “It’s a widespread idea in Western societies that as we get older, it’s normal to slow down, do less, and retire. Our message is the reverse: As we get older, it becomes even more important to stay physically active.” I learned of this research in Clarence Bass’s article “Born to Move- and Keep Moving“. There is also a good discussion of it in science daily here.
Lieberman, D, et al, “The active grandparent hypothesis: Physical activity and the evolution of extended human healthspans and lifespans”. Proceedings of the National Academy of Sciences, 2021; 118 (50): e2107621118 DOI: 10.1073/pnas.2107621118