The end of the hunter-gatherer era is too recent on an evolutionary time scale for the human genome to have adapted enough to accommodate the fundamental changes in diet, exercise and lifestyle that most modern societies have adopted. This 2-part series explores the mismatch between our ancient physiology and the modern western diet and sedentary lifestyle that underlie the majority of the diseases of today's western civilization, many of which have been virtually absent in hunter-gatherer and other non-westernized populations. The evolutionary medical and fitness theory proposes that by adopting a diet that mimics that of the hunter-gatherer (as described in Part 1 of this article), and by incorporating daily aerobic, anaerobic and strength exercises typical to hunter-gatherers (addressed in Part 2), we can effectively reduce the chronic degenerative diseases so prevalent in modern western society.
The scientific study of nutrition is a relatively new field, dating back less than a century. Loren Cordain has recently noted that nutrition is also a highly “fractionated, contentious field with constantly changing viewpoints on both major and minor issues that impact public health” (Lindeberg, 2009). Should we eat meat or not eat meat? Should we eat a diet high in protein and fat and low in carbohydrate or vice versa? A way to gain some clarity amid a myriad of differing viewpoints when choosing what foods to eat is to view nutrition from an evolutionary perspective. Indeed, renowned Russian evolutionary biologist Theodosius Dobzhansky wrote in 1973 that "nothing in biology makes sense except in the light of evolution." This first article in the series will explore human nutrition and health through that evolutionary lens.
Just over 25 years ago, Boyd Eaton and Melvin Konner published an article entitled “Paleolithic Nutrition: A Consideration of Its Nature and Current Implications” (Eaton & Konner, 1985). This was among the first of many papers to explore what would later become known as the Paleo or hunter-gatherer diet. Drawing on modern studies of hunter-gatherer tribes in remote parts of the world and archaeological evidence, the authors proposed what they called the “discordance hypothesis,” which states that from 2.4 million years ago to 11,000 years ago, humans evolved a specific genome that has only changed approximately 0.01 percent in the last 10,000 years. They argue that our current genome evolved to adapt to conditions that no longer exist and that the change occurred too rapidly for adequate genetic adaptation – in other words, our genes are 99.9% Paleolithic (Cordain et al., 2003). In contrast, modern society began to introduce mass agriculture, grains and grain products, sugars and sugar products, dairy and dairy products, and an enormous amount of processed foods as a regular part of the human diet. The resulting mismatch helps to cause chronic diseases and conditions such as heart disease, type II diabetes, pulmonary disorders, lung and colon cancer, hypertension, obesity, diverticulitis, and dental decay (Cordain et al., 2003; Carrera-Bastos, et al., 2011).
Other studies published around that time support the central ideas of the hunter-gatherer theory. One study showed that hunter-gatherers had high aerobic fitness, low cholesterol and no incidence of type II diabetes (Eaton et al., 1988) and another study showed that former hunter-gatherer aborigines, now sedentary with type II diabetes, showed marked improvement in fasting and postprandial glucose and insulin and lower fasting triglycerides when they were returned to their hunter-gather lifestyle for seven weeks (O’Dea, 1984).
As with all new theories, the Paleolithic diet has also received its fair share of criticism. The most common challenge to the applicability of the Paleo diet in today's world relates to the short lifespan of the hunter-gatherers, which was 30 to 35 years on average. It’s argued that primitive hunter-gatherers never lived long enough to experience chronic diseases such as heart disease and cancer, which take many decades to express themselves. However, the average short lifespan was due not to the absence of elderly people, but to the extremely high infant and child mortality rates. Death in the hunter-gatherers was primarily due to infectious diseases that are now controlled or related to the accidents and trauma of a life spent living outdoors without modern medical care, as opposed to the chronic degenerative diseases that afflict modern societies (Konner & Eaton, 2010).
Older hunter-gatherers rarely got or died from heart disease, type II diabetes or pulmonary disease. Hunter-gatherers were not healthier in absolute terms, but lacked the “diseases of civilization” that are prevalent in modern society (Eaton et al., 2002). In most hunter-gatherer populations today, approximately 10-20% of the population is 60 years of age or older. These elderly people have been shown to be generally free of the signs and symptoms of chronic disease (obesity, high blood pressure, high cholesterol levels) that universally afflict the elderly in western societies. However, when these people adopt western diets, their health declines and they begin to exhibit signs and symptoms of “diseases of civilization” (Eaton et al., 2002).
Some critics also argue that human evolutionary adaptation has resolved the mismatch between the human diet and nutritional needs since the hunter-gather era. And it is true that genetic evolution has continued since modern humans left Africa between 100,000 and 50,000 years ago. For example, there are obvious pigmentation changes of the eyes, hair and skin, intestinal lactase retention beyond infancy, enabling many to handle milk without challenging the health, adaptive defenses against microorganisms, and recent studies have shown subtle genetic adaptations for suitability to consume cereal grains or roots and tubers (Hancock et al., 2010). However, the core biochemical and physiological processes of the hunter-gatherer have been preserved. In other words, we have not adapted to thrive on a modern, highly processed, energy-dense, nutrient-poor, phytochemically-limited, manufactured diet. The millions of preventable deaths each year are attributable to modern dietary and other lifestyle factors that are very different from hunter-gatherers' (Eaton et al., 2002; Konner & Eaton, 2010).
Characteristics of the Hunter-Gather Diet during the Paleolithic Era
Konner & Eaton (2010) have outlined the characteristics of the hunter-gather diet, based on availability:
- Insects, fish, shellfish and other marine animals, reptiles, birds, wild terrestrial mammals and eggs
- Plant leaves, seaweed, seagrasses and algae
- Berries and wild fruits
- Nuts and seeds
- Honey (occasional intake)
Foods not available
- Dairy (except for human milk during weaning)
- Cereal grains (with the exception of occasional intake in the upper Paleolithic)
- Legumes (except certain varieties that were consumed seasonally)
- Isolated sugar
- Isolated oils
- Refined salt (even sea salt would be available only for shore-based populations who may have dipped their food in sea water)
Table 1. Estimated Nutrient & Macronutrient Intake of Hunter-Gatherers
(Konner & Eaton 2010; Carrera-Bastos, et al. 2011; Eaton, Cordain & Sparling, 2009).
|| >70 g/day
The Hunter-Gatherer Food Pyramid
- BASE: fruits and vegetables
- 2ND TIER: meat and fish
- 3RD TIER: whole grains, legumes and dairy products (although even these were very unusual for hunter-gatherers)
- TOP TIER: fats, oils, and refined carbohydrates (very limited, essentially functioning as condiments in a healthy diet)
Several studies have examined the effect of adopting a Paleo diet on various markers of health. Frassetto et al. (2009) showed that after 10 days of consuming a hunter-gatherer diet, subjects had reductions in blood pressure, improved arterial compliance, improved insulin sensitivity, a 16% reduction in cholesterol and 22% reduction in LDL-C.
In a 12-week randomized controlled clinical trial, Lindeberg et al. (2007) examined 29 patients with heart disease and either glucose intolerance or type II diabetes. Participants were given either a Paleolithic diet or a Mediterranean diet which included whole grains, low fat diary, vegetables, fruits, fish, and oils. The authors found that here was a 5.6 cm waist circumference reduction in the Paleolithic group compared to 2.9 cm reduction in the Mediterranean group. Independent of the weight loss, the Paleolithic group showed a 26% improvement in glucose tolerance/insulin sensitivity, compared to 7% in the Mediterranean group.
In another randomized controlled trial, 13 patients with type II diabetes consumed either a Paleolithic diet or a diabetes diet according to the American Diabetes Association guidelines for 3 months. Compared to the diabetes diet, the Paleolithic diet produced lower HbA1c, triglycerides, blood pressure, weight, BMI and waist circumference and higher HDL-C (Jonsson et al., 2009).
Fundamental changes in diet and lifestyle have occurred after the era of the hunter-gatherer — especially after the Industrial Revolution and the Modern Age — that are too recent on an evolutionary time scale for the human genome to have completely adapted. As a result, 99.9% of our genetic profile is still Paleolithic. This mismatch between our ancient physiology and the western diet and sedentary lifestyle underlies most of the diseases of civilization: heart disease, certain cancers, type II diabetes, autoimmune disease and osteoporosis which are virtually absent in hunter-gatherer and other non-westernized populations. By encouraging your clients to adopt healthy nutritional practices in line with those discussed above, you can have a positive impact on their long term health and longevity. Part 2 of this article will dive deeper into the fitness implications of the hunter-gatherer lifestyle, including practical recommendations for daily aerobic, anaerobic, and strength exercise options for your personal training clients.
- Carrera-Bastos et al. (2011). The western diet and lifestyle and diseases of civilization. Research Reports in Clinical Cardiology 2: 15–35.
- Cordain L., Eades M.R. & Eades M.D. (2003). "Hyperinsulinemic diseases of civilization: more than just Syndrome X". Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology 136 (1): 95–112.
- Eaton, S.B., Cordain, L. & Lindeberg, S. (February 2002). Evolutionary Health Promotion: A consideration of common counter-arguments. Preventive Medicine 34 (2): 119–23.
- Eaton, S.B. & Konner, M. (1985, Jan 31) Paleolithic nutrition. A consideration of its nature and current implications. New England Journal of Medicine 312(5): 283-9.
- Eaton, C. & Sparling. (2009). Evolution, body composition and insulin receptor. Preventive Medicine 49: 283–285.
- Jönsson, T., Granfeldt, Y. & Ahrén, B. et al. (2009). Beneficial effects of a Paleolithic diet on cardiovascular risk factors in type 2 diabetes: a randomized cross-over pilot study. Cardiovasc Diabetol, 8: 35.
- Konner & Eaton. (2010). Paleolithic Nutrition: Twenty-Five Years Later. Nutrition in Clinical Practice 25: 594-602.
- Lindeberg, S. et al. (2007). A Palaeolithic diet improves glucose tolerance more than a Mediterranean-like diet in individuals with ischaemic heart disease. Diabetologia 50: 1795-1807.
- Lindeberg, S. (2009). Food and Western Disease. Wiley-Blackwell.
Additional Reading and Paleo-Inspired Recipes
- Cordain, L. (2010). The Paleo Diet: Lose Weight and Get Healthy by Eating the Foods You Were Designed to Eat. Wiley; Revised Edition.
- Cordain, L & Stephenson, N. (2010). The Paleo Diet Cookbook: More than 150 recipes for Paleo Breakfasts, Lunches, Dinners, Snacks, and Beverages. Wiley.
- Lindeberg, S. (2009). Food and Western Disease. Wiley-Blackwell.