Examining the differences between the lifestyles of modern humans and early hunter gatherers reveals some surprising results.
A direct comparison of physical activity levels by Cordain et al. (1997) indicates that the variables in lifestyle lead to an average energy expenditure of 4.4 kilocalories per kilogram per day in sedentary office workers, as compared to an estimated 24.7 kilocalories per kilogram per day in hunter-gatherers. This “…denotes activity levels (in contemporary society) which have previously not been encountered in our species and which are clearly discordant with our genetic requirements.” (Cordain et al, 1997).
Chakravarthy and Booth (2004) state that a modern caloric intake is lower than that of our ancestors (a reduction of up to 1200kcal per day), though a positive caloric balance non-the-less exits due to physical inactivity. In fact, 70% of the sources of calories in a typical modern diet were unavailable during human evolution (Lindeberg, year unknown). This 70% of our diet is high in fat and salt, major contributors to coronary heart disease. Thus, not only does our contemporary environment appear pathogenic due to the increases in obesity, but also in terms of fatty acid and sodium intake. Cordain et al. (1997) found that saturated fatty acids comprised 5% of the total energy intake of hunter gatherers, while this number jumps considerably to 15% in westernised diets. Cordain et al. (1997) states that it is these fatty acids which raise cholesterol, leading to atherosclerosis. Additionally, O’Keefe et al. (2004) suggest a five fold increase in sodium intake, further contributing to cardiovascular disease. These drastic changes in physical activity levels and caloric intake have lead to radical differences in body composition between pre-hominids and industrialized populations. Modern man has a markedly higher sarcopenia level than our ancestors (Cordain et al., 1997), leading to both a drastic change in insulin sensitivity and an increase in the incidence of cardiovascular disease, caused by a change in calories consumed and a decrease in physical activity (Batchelder, 2000).
As previously mentioned, the goal of a hunter-gatherer’s lifestyle was to maximise energy intake and minimize energy output, with the reality being a low energy intake and high output. In modern populations, the goal has remained the same, not due to a conscious decision, but due to our genetic predisposition. We have begun to control our own environment, and as a process of this we have reached our evolutionary goal, achieving maximum energy intake and minimum energy output. Upon reaching this goal, we have crossed a “threshold of biological significance” (Chakravarthy and Booth, 2004) whereby a combination of our environment and our disease susceptible genes results “…in the individual being affected with overt clinical disease.” (Chakravarthy and Booth, 2004).
A modern lifestyle involves exercise as a leisure activity, a time-governed addition to other daily activities. Conversely, a hunter gatherer has a direct correlation between physical activity and diet, making physical capacity as much of a necessity as food procurement. Regardless of the substantial changes in lifestyle over the last 40,000 years, our “…exercise capacities, limitations and requirements…” remain the same, with mitochondrial DNA comparisons from diverse ethnic groups (Cordain et al. 1998) indicating little if any change in genetic constitution. Without these norms, diseases of civilization (Batchelder, 2000) are inevitable.
The genes selected for function and survival in the late Paleolithic are now being exposed to “…sedentary lifestyles, fat-rich and fibre-poor diets, positive caloric imbalance, and an extended lifespan, all of which result in a selective disadvantage…”(Chakravarthy and Booth, 2004), leading to hypertension, atherosclerosis, hypercholesterolemia and other chronic health conditions.
