I just finished reading the fascinating book Exercised: Why Something We Never Evolved to Do Is Healthy and Rewarding by evolutionary biologist Dr. Daniel Lieberman. His main point is that humans evolved doing physical activity as part of their daily lives, hunter gatherers walking a lot, digging for tubers, climbing trees for fruit, or running after prey, and subsistence farmers working a lot in the fields. The evidence is that several hours a day were spent being highly active, from brisk walking to occasional sprinting or physically demanding work like digging in tough soil with a stick or carrying heavy objects.
But our remote ancestors never did formal exercise during leisure time, they rested. The notion of exercising when they didn’t have to would not have crossed their minds. Resting when we don’t need to work is a survival mechanism, our ancestors needed to save their energy for when it was needed. But while they may have sat a lot, it was probably not continuously for long periods. Hunter gatherers did a lot of camp chores, repairing tools, preparing food, etc. This may be done while not standing but it is not totally inactive. And they probably didn’t sit for long in the same position, but got up and moved to the next chore. This is interesting in light of current recommendations not to sit for too long (“sitting is the new smoking”).
The instinct to rest when we can is analogous to the fact that we are predisposed to eat a lot when food is abundantly available, and store fat to help us to survive future times of scarcity. This is not helpful in modern times when food is always available in excess. Similarly, the instinct to rest is maladaptive in modern times because we never have to move much at all, except to walk to the fridge or out to our cars.
One interesting point is why did we evolve to live beyond our child rearing age at all, if the whole point of evolutionary adaptations is to pass on our genes? He discusses this in detail. It turns out grandparents contribute quite a bit to the survival of the group. Among hunter gatherers, for example, mothers with young children have trouble gathering enough calories to support themselves and their children, especially when they are constrained with babies they are carrying around. It helps to have other members of the group who can gather excess food to share, and there is ample evidence grandmothers played this role. Elders also contributed through their accumulated wisdom, like tracking techniques or where to find water. This is something that is often lost in modern society when we “warehouse” our elders in nursing homes. But the main thing to consider is that it is not natural for people to become less physically active as they age.
Whether it is healthy or not in our current to be sedentary, it is a natural instinct that we have to fight to become active. He does review some ways traditional cultures participate in leisure time activity. One is dancing, which is sometimes done in traditional cultures for hours, late into the night. Another is play, which is obviously done by the youth (humans as well as other species). But in many societies participation is some kind of sport also persists into adulthood.
He spends an entire chapter on “how to make exercise happen in the modern world”, and comes up with some strategies. Finding a way to make it fun is an obvious one. In my opinion he missed another obvious approach: active transportation. Up until the early 1900s it was not possible for most people, except perhaps the wealthy, to be “couch potatoes”. Even people who worked in an office still had to get there, which involved lots of walking.
Dr Lieberman coins the phrase “exercists” for people who like to nag us to exercise, or brag about their exercise (or both). I believe about many things in life, to paraphrase Ben Franklin, “Neither a Nagger Nor a Bragger Be”. I hope I do not come across as either. My desire is to pass on the information why exercise is important, to show ways to make it fun (which I believe is crucial to make a successful habit of it), and to inspire people to do it. When I talk about my own adventures in keeping active (which are after all pretty mediocre by elite standards), it is only to show what is possible for an aging human that is not particularly talented.