An Evolutionary Approach To Preventive Medicine: Counter Arguments Against The Theory
Increasingly, people around the world are becoming aware of the benefits of the Palaeolithic (“paleo”) diet. This diet, notably free of grains, dairy products, pulses, and legumes (amongst other staples of the modern diet) is the one practiced by our Stone Age ancestors prior to around 10,000 years ago, when farming was first introduced. But could the diet be just one aspect of the late Palaeolithic lifestyle that could be of benefit to us today? And could our ancestral experience also serve as a model for modern disease prevention and health promotion? The underlying principle of the paleo diet is that, whilst the human body has genetically changed very little in the past 10,000 years, our eating habits and lifestyles have changed drastically; and this has put considerable stress on our bodies and led to what we see playing out today: a rapid upsurge of degenerative chronic diseases, such as type 2 diabetes, cardiovascular disease, and cancer. The theory that our ancestral experience could provide valuable insight into modern health problems has gained a lot of ground in the past couple of decades. But elsewhere (particular within the medical establishment) the theory is discounted out-of-hand. There is enough interest in the subject to provide solid counter arguments to the points made against the theory – and the main arguments are summarised below.
The basis of most arguments against…
Opinions against an evolutionary approach to preventative medicine are largely based on three main factors:
- Comparative life expectancy
- Potential genetic change since the introduction of agriculture
- Innate human adaptability to different environments
A paper by S.Boyd Eaton, Loren Cordain, and Staffan Lindeberg, published in 2002, challenged these three main arguments against such an evolutionary approach to health. Their arguments are summarised below…
Comparative life expectancy
If the Palaeolithic diet, level of physical exercise, and so on, really made for a healthier lifestyle, then why do people in affluent countries live longer today than then?
And isn’t the prevalence of chronic disease simply down to people living longer – allowing these agerelated diseases to take hold much more commonly?
This is the most commonly made case against the theory but it is a somewhat banal argument. The authors point out that the major factor that dictates wild swings in average life expectancy is infant mortality.
It actually makes little difference to average life expectancy if people generally die at 75 or 80:
“Completely eliminating the major known risk factors for nine leading chronic diseases would increase life expectancy at birth by only 4 years.”
When infant mortality is high, as it is in many developing countries today, low average life expectancy is the result. When large amounts of people die before they reach the age of two, it impacts average life expectancy much more than people dying late in life from chronic disease.
The other point about chronic degenerative diseases is that, while they frequently impact people in old age, they actually start quite early in life: obesity, rising blood pressure, and insulin resistance can all be traced early in life and are biomarkers for chronic disease.
These biomarkers are common amongst young people in modern affluent countries. Yet they are rarely observed in modern hunter gatherer tribes, whose lifestyle has changed little in the past 10,000 years. Many such tribes have been the subject of interesting and relevant studies.
Potential genetic change
Despite 400-500 generations of human beings since late Palaeolithic times, the human genome appears to have changed little (though the idea cannot be excluded).
There are good examples of other mammals changing significantly in much less time – for instance, woolly mammoths in Wrangel Island shrank to a third of the size of their mainland cousins over a period of 5000-7000 years.
This would seem to suggest a clear potential for the same to have occurred in humans.
But it hasn’t happened, according to the authors:
“Respected geneticists, paleoanthropologists, biologists, and evolutionary theorists concur that, genetically, contemporary humans differ little from our Stone Age ancestors.” “There has been ample time for important changes in the human gene pool since the Neolithic Revolution, but comparative genetic data provide compelling evidence against the contention that long exposure to agricultural and industrial circumstances has distanced us, genetically, from our Stone Age ancestors.”
Innate human adaptability to the environment
While there were differences in ancestral environments around the world and over the large period of time from 50,000 years ago until 10,000 years ago, these differences “were minor compared with their essential similarities”.
The point is made that, whether our Stone Age ancestors lived in the arctic or the tropics, 10,000 or 500,000 years ago, they still had to hunt or forage for their food. This required intense physical exertion – unlike modern lifestyles.
The authors state that:
“Ancestral lifeways during the environment of evolutionary adaptedness were indeed heterogeneous, but their core essentials were basically similar and differed strikingly from those of the present.”
Humans are considered one of the most adaptable of all mammals – and some people speculate that this adaptability is partly responsible for the fact that there are now 500 people alive for every human alive at the end if the Stone Age.
With such powers of physical and cultural adaptability, they claim that we’re also easily able to adapt to the modern environments of affluent societies. This is not an unreasonable claim but whether we have been able to adapt biologically to these new environments is far less certain.
The authors note:
“As a rule, organisms are healthiest when their life circumstances most closely approximate the conditions for which their genes were selected.”
They speculate that “an individual organism’s adaptation may sacrifice future health for short-term survival.”
“Conditions tolerable or even beneficial in early life may lead, eventually, to chronic degenerative diseases.”
Individual lifestyle choices are the key to the prevention of chronic degenerative disease. And the Palaeolithic lifestyle, in particular, deserves attention in terms of its potential to prevent disease and promote health.
The authors of the above paper suggest that the theory is an “attractive, potentially fruitful paradigm that deserves discussion and research evaluation.”
This seems entirely reasonable while dismissing the theory out-of-hand does not.
S. Boyd Eaton et al. Evolutionary Health Promotion: A Consideration of Common Counterarguments Prev Med. 2002 Feb;34(2):119-23.