Life Expectancy of Hunter Gatherers (Paleolithic Humans)

I was first tipped to this by Chris at Conditioning Research, but thanks still go to Henry, a reader of Mark’s Daily Apple who recently provided a link to UC Santa Barbara anthropology professor Michael Gurven and University of New Mexico professor Hillard Kaplan’s three year old paper on life-expectancy in paleolithic humans.

The paper, entitled “Longevity Among Hunter Gatherers: A Cross-Cultural Examination” [Population and Development Review 33:2 (2007) 321-365; online PDF available here], is a gold mine for anyone interested in the question of paleolithic lifespan (not only in terms of data and analysis, but also bibliography).

In my experience, the average person on the street assumes that so-called cavemen typically lived to “about 30 years of age.” This widespread assumption leads many people to reject the “paleo-diet” or “caveman diet” for the simple reason that we have no reason to believe that paleolithic human beings lived longer or had a better quality of life than modern humans. This article provides a ready rejoinder to that point of view.

During the past several decades, many anthropologists have advanced a new view of paleolithic life expectancy. Kaplan and Gurven’s comprehensive study argues that the limits of human lifespan and the curve of average rates of mortality during different life stages may just be an evolved characteristic of our species, that has been present since paleolithic times if not longer.

A quote from the opening section of the paper:

Our conclusion is that there is a characteristic life span for our species, in which mortality decreases sharply from infancy through childhood, followed by a period in which mortality rates remain essentially constant to about age 40 years, after which mortality rises steadily in Gompertz fashion. The modal age of adult death is about seven decades, before which time humans remain vigorous producers, and after which senescence rapidly occurs and people die. We hypothesize that human bodies are designed to function well for about seven decades in the environment in which our species evolved. Mortality rates differ among populations and among periods, especially in risks of violent death. However, those differences are small in a comparative cross-species perspective, and the similarity in mortality profiles of traditional peoples living in varying environments is impressive.

In other words, the authors argue that, already by the end of the paleolithic era, humans had evolved into beings who can live productive lives well into their sixties, declining after their seventies. Modern humans have of course inherited this genetic, evolutionarily determined lifespan.

A mortality curve is a diagram of the changing rates of death for any given age group. The curve of human mortality, cross-culturally, is shaped like a saddle. Mortality rates typically start relatively high (defenseless infants are vulnerable to a variety of mortal threats), but decline rapidly in childhood. They continue to decline until early adolescence, then remain constant until middle age, and then begin to rise again, as the elderly succumb inevitably to entropy. In any population, ages of people run the gamut from infants to octogenarians and beyond.

Intuitively, the paper’s findings make sense. Our species spent several million years living as technologically advanced apes, in the mode of nomadic or semi-nomadic hunter-gatherer bands. During this period people did not typically “die at age 30.” In spite of the very real mortal threats faced by early humans — threats of death by accident, violence, disease, or catastrophe — the species evolved in a way that a human person can remain productive and vital into his or her sixties, and may easily live beyond that point, even though the decline into death is inevitable and the risk of death accelerates after age 70.

This was as true of “cavemen” as it is of modern humans.

Myth and Mortality

One thing that has changed, however, for modern humans is the mythic world-view adopted around the topic of death. Many ancient cultures had a mythic view of that accepted and explained inevitable death in light of some notion of cosmic order and purpose. But modern humanity seems to have embraced a radically different myth, one that is wrong, at least in its history. Our modern myth is a narrative of progress in lifespan. “Cavemen,” we say, lived lives that were nasty, brutish, and short quoting the philosopher, whereas modern humans will live ever longer lives. Death itself may be conquered by using a science of diet or medicine. So we tell ourselves. And we obsess with extending our span of life.

The article linked above may provide a useful corrective to the modern myth of the ever expanding length of human life, by helping to dispel the misconception that ancient humans lived pathetically brief lives in comparison with us lucky moderns.

Ironically, through the epic story of human origins told in Genesis, the Judeo-Christian tradition embraced precisely the opposite narrative: a story of decline in lifespan. According to Biblical epic, in the pristine beginnings of humanity, the first human and his spouse had access to the Tree of Life — a food that granted immortality. In theory they had endless lifespans. After being cursed by God and prevented from gaining access to that tree, the lifespans of the first couple turned out to be much longer than the average lifespans of their descendants, until, after a number of generations had passed, and the time of the flood had arrived, the maximum lifespan of human beings was finally reduced to the comparatively short period of one hundred and twenty years (Gen. 6:3).

The presence of this number 120 in the Biblical epic suggests that ancient peoples (the story is 3000+ years old) had a relatively accurate sense of the longest possible human lifespan. The figure 120 is quite realistic, as can be seen by looking at the list of the ten oldest verified people ever (see Wikipedia). Ancient peoples cannot have arrived at this notion of a “maximum lifespan” except through long experience with the phenomenon of human aging and its relationship to mortality.

In other words, the elderly were not unknown in ancient times, nor they missing from paleolithic human communities. Human beings have always grown old and died of “old age.” Only a modern conceit, one that accepts without criticism the inflated claims of the superiority of our “scientific” civilization, would deny this.

Recommended Additional Reading: “Paleo Life Expectancy” on Primal Wisdom.

Let me know what you think...