In modern, industrialized nations such as the U.S., Scotland, and Sweden, few people above the age of 55 are completely disease-free. The vast majority suffer from one or more health problems, whether it’s hypertension, diabetes, and/or hypercholesterolemia, and use one or more medications. This has led a lot of people, including many scientific researchers, to assume that disease is intrinsic to the normal human ageing process. Concepts such as antagonistic pleiotropy, which refers to situations where a gene has divergent effects on organismal fitness at different points in life, and the idea that it’s a lot more important, from a Darwinian point of view, to be healthy and vibrant early than late in life, as reproduction typically occurs early on, are often invoked so as to explain this phenomenon.
At first glance, this may seem like a reasonable evaluation of the situation; however, upon closer inspection, it becomes clear that it has a couple holes in it, two of which are particularly large. First of all, it’s overlooked that the aforementioned disease-heavy public health situation doesn’t represent the evolutionary norm for our species, and that in natural environments largely unperturbed by man, such a degree of illness is unheard of. Secondly, little emphasis is placed on the fact that it’s generally better, from a fitness perspective, to be old and healthy than old and sick.
Is disease inherent to the human ageing process?
Over the years, I’ve delved into a number of books, studies, and review papers that cover the health situation of traditional, non-westernized people (e.g., hunter-gatherers, traditional horticulturalists), including Dr. Weston A. Price’s seminal publication Nutrition and Physical Degeneration. One of the things that consistently stands out in the reports of travelers, researchers, and explorers who’ve visited primitive cultures who’ve retained various essential components of the ‘original’ human lifestyle is that the people who belong to such cultures tend to be healthy and largely free of chronic disease. Of note, hunter-gatherers rarely succumb to cancer and exhibit exceptional cardiovascular health. Importantly, this not only appears to be true for the younger population, but it also to a large extent applies to the elderly (1, 2, 3, 4, 5).
For example, during his examinations of the Kitavan Islanders, the late Dr. Staffan Lindeberg found that healthy ageing appeared to be the norm rather than the exception (2, 6, 7, 8) . Conditions such as cancer, ischemic heart disease and stroke were largely unheard of on the Island, and the elderly seemed to be very robust and fit for their age, even though many of them smoked quite a bit of tobacco.
Similar findings are reported other places, such as in Dr. Price’s masterpiece. If I remember correctly, he says in his book that many of the primitive peoples he visited on his travels didn’t even have a name for most of the degenerative diseases that plague westernized communities. Not because nobody was old enough to get such diseases, but rather because they simply didn’t exist. There’s no reason to think that the situation was any different in the distant past. If anything, degenerative disease was most likely even less of a concern back in Paleolithic times, when there was a very high degree of genome-environment congruence.
This is not to say that disease is completely unheard of among elderly, traditional people, or that the elasticity and robustness of the human body doesn’t decline with age; however, it does highlight something very important, and that is that it is possible to grow fairly old without succumbing to disease. It clearly suggests that the degenerative disease load that we experience in industrialized parts of the world is an anomaly in evolutionary regards.
That said, it’s important to note that hunter-gatherers and other traditional people generally don’t live into their 80s or 90s, which is why I put an emphasis on the word fairly above. They certainly don’t die at the age of 30, as some people may think; however, given that they survive past infancy, it appears that they tend to throw in the towel when they’re about 70 (sometimes a bit earlier, sometimes a bit later) (5). This has led some authors to suggest that…
… human bodies are designed to function well for about seven decades in the environment in which our species evolved. (5)
The obvious caveat here is that the hunter-gatherer populations that have been studied in modern times don’t live under exactly the same conditions as the ones our primal forebears lived under. Furthermore, they are not genetically identical. In other words, general inferences related to human ageing in an evolutionary context that are based on the results of such studies should be taken with a pinch of salt. I don’t find it likely that humans were designed to function well for less than seven decades under settings of genome-environment concordance; however, it may be that they can function well for a bit longer.
Why is healthy ageing the norm, rather than the exception, among traditional people who live under natural conditions?
We humans have a tendency to accept the conditions we live under, thinking that they constitute normalcy. Hence, it’s not surprising that we tend to try to explain the world on the basis of the things we can observe around us, which is exemplified by the line of reasoning described in the introduction of this article.
From a westerner’s point of view, it may seem odd and irregular that so many elderly, traditional people stay healthy all the way through life, given that such a situation differs markedly from the one he’s used to. From an evolutionary point of view, however, a different picture emerges. From such a standpoint, it immediately becomes clear that it’s the situation that exists in modern, industrialized nations that is irregular, not the one that exists in nature.
It’s not really that surprising that humans who live under conditions that resemble the natural conditions under which we evolved for millions of years prior to the rise of the modern civilization aren’t riddled with diseases or health problems, given that it’s generally a major advantage to be healthy rather than sick in a Darwinian sense. This is not only true early in life, but it also to a significant extent applies late in life. There are many reasons why this is the case.
Not only will sick people find it difficult to care and provide for others, such as for example offspring or grandchildren, but they will require the care of others, in the sense that they need food, shelter, and comfort, all of which they’ll likely have trouble procuring on their own. This is obviously relevant in evolutionary contexts, as it affects fitness-related parameters. An old hunter-gatherer who’s energetic and healthy enough to devote ample time to the care of closely genetically related individuals is obviously going to be at an advantage in the context of inclusive fitness as compared with someone who puts a strain on his/her kin. Also, it’s important to remember that men are often able to reproduce late in life.
In light of this assessment, which represents another reason why health matters (a lot) in evolution, the finding that people who live under natural conditions tend to age in a healthy manner doesn’t come as a surprise. On the contrary, it’s exactly what one would expect. This is not to say that it’s equally important, in a Darwinian sense, to be healthy late in life as early in life; however, it clearly suggests that natural selection does “care” about the health of older people, in particular those who live under conditions where kindergartens, elderly care facilities, and hospitals are absent.
Furthermore, it suggests that the main reason why the bodies of most old people in countries such as the U.S., Scotland, and Sweden are riddled with disease isn’t that disease is inherent to normal ageing, but rather that our bodies don’t fare so well in the manufactured, technologically-driven environment we’ve created for ourselves. The central driver of unhealthy ageing that’s fueled by this mismatch is inflammation, which has been implicated as a causal factor in virtually all degenerative diseases (9, 10, 11, 12).
It’s often assumed that disease is an unavoidable part of the human ageing process, in large part because the vast majority of old people in the world today suffer from several health problems and rely on various pharmaceutical drugs to get by. What’s often overlooked is that this situation is not representative of the situation that exists in nature, in the sense that hunter-gatherers and other traditional, non-westernized people rarely get degenerative diseases such as heart disease and cancer, even though they often live well into their 60s or 70s. This isn’t particularly surprising in light of the fact that it’s better, from a Darwinian point of view, to be healthy than sick, irrespective of one’s age, and clearly suggests that many of the health woes that plague old people today develop as a result of genome-environment incompatibilities.