An evolutionary perspective on the workout routine
On the workout routine through the ages — Part 1 of 8
From an evolutionary perspective, we can infer that humans are as adapted to physical activity as they are adapted to inactivity. Because adaptations do not directly promote health, and natural selection never operated to limit negative consequences of chronic physical inactivity — which was rare until recently — biological evolution developed neither an optimal nor a minimal workout routine to keep health issues in check for which inactivity is a major risk factor today.
There is no single entry point into the universe of human physical activity and inactivity. But biology and an evolutionary perspective can be anything but wrong to cast first light onto the subject.
As a matter of definition, evolutionary adaptations are all novel features of an organism that are shaped by natural selection (what can be observed to the present day) and improve the organism’s ability to survive and reproduce. Such adaptations do not directly promote health. They do so only to the extent that health promotes an organism’s success to sustain life and producing offspring that can survive and reproduce.
The theory of natural selection and the concept of adaptation explain why humans evolved to be endurance athletes — when required, to be precise. From this statement, we cannot deduce that humans are not equally adapted to rest whenever possible. We actually are.
Evolution turned early humans — in contrast to other primates — into well-adapted organisms to pursue regular physical activity that is dominated by endurance as opposed to power, including trekking over long distances, running fast, carrying stuff, and throwing things. This change happened with the rise of homo erectus who evolved to be the first hunter-gatherer in times of climate change some two million years ago. Evolutionary adaptations of the bipedal homo erectus let him trek up to 15 kilometers per day to forage enough food. They included long legs and an improved pelvic skeleton. Expanded gluteus maximus and short toes are strong evidence of endurance running skills. Because hunting tools appeared as early as 500,000 years ago it is next to certain that endurance running made persistent hunting possible through a combination of seeking prey while trekking and chasing it while running. This was a very energy-intensive activity but the only effective way to hunt larger animals for almost 1,5 million years.
Simulation data about the energy budgets of hunter-gatherer populations tells us that the average total energy expenditure was 2,600–3,000 kcal per day for males. The male resting metabolic rate amounted to roughly 50% of the total energy expenditure which allows us to reason that the active energy expenditure relative to body mass was 30 kcal per each kilogram and day, which was twice as high as the active energy expenditure of the average male in the Western regions today (we have to keep in mind that hunters-gatherers had lower body masses than people in the 21st century). The average total energy expenditure of a female hunter-gatherer was 500 kcal lower than that of her male counterparts. But we have to include some additional 1,000–2,000 kcal per day for pregnant and nursing females.
Because food was not as abundant as it is today and energy obtained from it was also quite limited, the energy allocation model indicates that hunter-gatherers struggled to stay in energy balance. For this reason, they minimized physical activity to 4–6 hours per day (which was still way more compared with other primates) and remained inactive for the rest of the time. Their body mass index was less than 23, but we have to be aware of one significant difference. Their bodies stored as much fat as possible (10–15% for males and 15–25% for females) to catabolize it during seasons of food scarcity. Hence, it is easy to see that extraneous physical activity was maladaptive under such conditions.
Sure, one can always argue that the paleolithic lifestyle did lack sufficient comfort and convenience. But scientific research indicates that it was far from being lethal. Hunters-gatherers could expect to live to their 70s and older provided that they survived childhood. As they aged they continued to be physically active. Moreover, studies provide strong evidence that the many chronic noninfectious diseases of our times such as coronary diseases or osteoporosis — for which physical inactivity constitutes a major risk factor — were considerably less prevalent among hunters-gatherers and later populations compared with current numbers because pathological physical inactivity was a rare phenomenon until very recently.
From an evolutionary perspective, physical inactivity was a desirable effect of trading off limited energy in such a way as to support survival and reproduction in the first place. While physical activity is without any doubt an effective measure to promote health (it established the anatomical, physiological and cognitive capacity of the hunter-gatherer), biological evolution developed neither an optimal nor a minimal workout routine to keep health issues in check because health benefits were a byproduct of endurance activity that was itself undertaken to restore depleted energy resources. So it is easy to see that natural selection never operated to reduce the negative consequences of chronic physical inactivity we suffer from today. It is a blind process and therefore it does not have to do us any favor.
Moreover, our innate behavior to avoid unnecessary exertion did not fade away. It explains why it is difficult for humans to adhere to workout routines today. Because we do not have to hunt and gather in the wild anymore and only need to buy — often highly processed and obesogenic — food from a place around the corner or within a short driving distance, the fundamental evolutionary stimulus to pursue regular physical activity has gone for good already a long time ago.
Main source: Daniel E. Lieberman (2015) Is Exercise Really Medicine? An Evolutionary Perspective. Current Sports Medicine Reports, 14, pp. 313–319.
