Lifespan
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There seems to be a lot of contention about human lifespan, particularly during hunter-gatherer times.
Currently, the world's mean (average) lifespan, across all countries, is 73 years (1). Not everyone knows this, and many people think it is higher. To be fair, this mean life expectancy is, of course, slightly higher in many western countries, and slightly lower in many non-western countries. However, even in the west, the average lifespan appears to be plateauing and, by some estimates, may have peaked already (2).
In 1651, the English philosopher, Thomas Hobbes, stated that life for anyone lacking the amenities of civilization, life would be "nasty, brutish, and short" (3). Somehow, almost everyone seems to accept this idea as a fact, one that has been propagated down the centuries. In 1961, the French anthropologist, Henri Vallois, specifically applied such a notion to our hunter-gatherer ancestors when he proclaimed that among early humans, “few individuals passed 40 years, and it is only quite exceptionally that any passed 50” (4).
So that is the truth - are Hobbes, Vallois and everyone else, correct? Let's have a look.
The Best Evidence
Whenever one is examining contentious issues, particularly in the face of sub-optimal data (as we cannot examine our hunter-gatherer ancestors, since they are no longer alive), it is usually optimal to focus on the best evidence available. With respect to hunter-gatherer mortality, an extensive 2007 study, written by a pair of United States anthropologists, Michael Gurven and Hillard Kaplan, arguably fits the bill (5).
Gurven and Kaplan examined a diversity of relatively isolated, small-scale populations still living ancestral lifestyles in several continents across the world, which was done in a "cross-cultural" manner. They picked both hunter-gatherers, as well as forager-horticulturalists that had adopted a degree of agriculture into their lifestyles. Their study sample represented the most complete set of pre-industrial populations available, and it was notably larger than any previous study that had been done until that time (or any I can find since). In essence, the modern populations they studied had lifestyles that were as similar as possible to those of ancestral times. |
Average modal (most common) ages of death for several modern hunter-gatherer and forager populations (5). |
Specifically, Gurven and Kaplan divided the populations into three groups. The first group, the hunter-gatherers, included populations such as the !Kung (from modern-day Namibia, Angola, and Botswana), the Hadza (Tanzania), the Ache (Paraguay), the Hiwi (Colombia), and the Agta (Philippines). The second group, the forager-horticulturalists, included populations such as the Tsimane of Bolivia. The third group, the acculturated foragers, included populations such as the Indigenous of Australia.
Following the analysis, Gurven and Kaplan determined that the average modal (most common) age of death for these populations was 72 years, with a range of 68–78 years. The most common causes of death were infective illnesses (70%), followed by homicide (20%). Only 9% of deaths were attributed to disorders such as the metabolic syndrome, atherosclerosis, and cancer, with little data available for neurodegenerative disorders (notably, these four disorders are now responsible for the vast majority of deaths in the west today). Since it was not uncommon for adults to reach the 70s, it was suggested that previous inferences, most of which were based on reconstructive data, were unreliable. |
Graph of the frequency distribution of ages of death, comparing ancestral populations with modern ones (5). |
So why did (and do) so many people see life as "nasty, brutish, and short" for these populations? The reason is that many of the deaths in the studied populations occurred during infancy and childhood (exceeding 50% in some of them), and these extremely young deaths skewed the mean age of death to a much, much lower number than what the average adult actually attained. In fact, by focusing on the mean age of death, it appeared as though most adults were dying in their 20s and 30s, when in fact most adults survived well into their 70s. In essence, simply looking at the mean confuses the issue - the mode gives us a more realistic idea of mortality under an ancestral lifestyle.
So with respect to the idea that life was nasty, brutish, and short, or that few people survived past age 50 years, the best evidence indicates that we should reject this hypothesis.
Why It Matters
Why does this matter? Well, the lifestyle disorders (metabolic syndrome, atherosclerosis, cancer, neurodegenerative disorders), which used to be rare, are now the major causes of death in the world (6). Yet modern hunter-gather populations still experience very little of these disorders, despite the fact that they have similar lifespans to modern adults. So their must be something about their lifestyles that mitigates the onset of these now all-too-common disorders.
Hunter-gatherers have many beneficial aspects to their lifestyle, which encourages hormesis (particularly, mitohormesis) (7). Perhaps the most salient aspect of this lifestyle, in terms of health, is the natural oscillation between feeding and fasting. Moreover, ancestral human diets are more based on wild foods (8), with 70-75% being low-carbohydrate, and another 20-25% moderate in carbohydrate (9). Only a smattering of these populations eat a diet high in carbohydrate, such as the Hadza (65% carbohydrate by energy intake) and Tsimane (72%) (10). However, even when an ancestral diet is high in carbohydrate, it has a lot more fiber in the diet, which mitigates glucose spikes and the effects of nutritional overload on the body. Beyond dietary lifestyle, hunter-gatherers also move more, and yet they also rest and sleep more, working fewer hours of the day and taking more leisure time compared to adults in modern civilizations. Furthermore, an under-appreciated aspect of their lifestyle is that hunter-gatherers have few "wants" (11), which I suspect dampens chronic stress, worry, and depression by more than a little bit.
Most hunter-gatherers died from infective illnesses, which particularly devastated the infants and children, followed by warfare and homicide. Given modern sanitation practices, antimicrobial treatments, and societal laws, none of these things are issues anymore. We now have an opportunity to adopt many of their ancestral practices so as to alleviate the ever-worsening pandemic of metabolic disease that is on the horizon, for which we are nowhere near prepared. If we can align the best from both worlds, past and present, I think we could greatly exceed not just the lifespan, but also the healthspan, of all people before us, both past and present.
And why does this matter? Quite simply, we need more healthy, wise people in the world. There are lots of intelligent young people, but few people over 80 years of age who remain highly functional. Currently, it is estimated that 40-50% of people in western countries will require an aged care facility after age 80 years, and it is the norm after age 85 years (12). This number is far too large. We need older people who are 80, 90, even 100 years old who are still cognitively, physically, and socially highly functional, so that they can inform and guide younger generations on the lessons of history, lessons they personally experienced themselves.
Given the rise of the information era, we (may) be more intelligent than ever, but I suspect the average (and modal) level of wisdom is decreasing. Without wisdom, intelligence offers a path to self-destruction. Wisdom is more important, and offers a better way.
Solace.
References
(1) https://www.worldometers.info/demographics/life-expectancy/.
(2) Lichtenberg. 2022. Reversing the Decreasing Life Expectancy: A National Health Priority. Mo Med 119, 321-323, 333.
(3) https://en.wikipedia.org/wiki/Leviathan_(Hobbes_book).
(4) Vallois. 1961. The social life of early man: The evidence of skeletons,” in S. L. Washburn (ed.), Social Life of Early Man. Aldine de Gruyter, Chicago.
(5) Gurven and Kaplan. 2007. Longevity Among Hunter-Gatherers: A Cross-Cultural Examination. Population and Development Review 33, 321-365.
(6) https://en.wikipedia.org/wiki/List_of_causes_of_death_by_rate.
(7) Phillips and Picard. 2024. Neurodegenerative disorders, metabolic icebergs, and mitohormesis. Transl Neurodegener 13, 46.
(8) Crittenden et al. 2017. Current views on hunter–gatherer nutrition and the evolution of the human diet. Am J Phys Anthropol 162, 84–109.
(9) Ströhle and Hahn. 2011. Diets of Modern Hunter-Gatherers Vary Substantially in their Carbohydrate Content Depending on Ecoenvironments. Nutr Res 31, 429-435.
(10) Pontzer et al. 2018. Hunter-gatherers as models in public health. Obes Rev 19, 24-35.
(11) https://en.wikipedia.org/wiki/Hunter-gatherer.
(12) Broad et al. 2015. Likelihood of residential aged care use in later life: a simple approach to estimation with international comparison. ANZ Journal of Public Health.
