It is generally thought that life expectancy in the past was less that it is today for our species as a whole and in the case of industrialized countries in particular. However, this belief counts as a falsehood not because it is untrue (it is, in fact, true) but because many people get this idea wrong in a few different ways. People often:

1) confuse life expectancy with lifespan;

2) underestimate the life expectancy of many past populations; and

3) think of the past compared to the present as a dichotomy, the present being one way, the past being the other way, failing to recognize diversity and variation in life history variables across our species and across time … life expectancy is seen as a measure of quality of life (which it may well be) that has tracked the one way progress of the human condition from a widespread past condition of short-lived misery to the present and much improved condition of living long and prospering.

As is the case with other bio-cultural variables such as stature, we often see the past as a particular (and often fairly immediate) past, which actually represents perhaps a few centuries at most and a few percent of the landscape across which our ancestors lived. And, in some of the most commonly conceived of ‘pasts’ … the English Middle Ages, Urban factory towns in the 19th century, some cave in France, etc. … it may well be true that short people experienced a life nasty brutish and short-lived. But in the meantime, in Australia, or South Africa, or the Amazon, or Mongolia, or Nebraska, or Kiribati, one thousand years ago or ten thousand years ago, entirely different things were happening.

Life expectancy is usually phrased as death expectancy, because it is often thought of as the average age of death of individuals of a certain age, estimated for a particular population and using empirical data. Technically, it is actually the number of years of life you have left, expressed as an estimated average for the individuals in your cohort and context. There are two commonly used frameworks for life expectancy: At birth and some later age, often 12 years old. In many populations, death is so common among infants and very young children that life expectancy from birth is a poor representative of what is really being considered, so life expectancy from a later (non-zero) age is more meaningful.

Life span is how long you live. Life expectancy and life span really are, in an informal sense, the same thing (or at least are often treated that way), but life span is usually conceived of by the human on the street as how old the old people are, or how long an individual person (or thing) potentially lives, as opposed to an average. In fact, sometimes life span is thought of as a maximum (the human life span is something like 120 years, because that’s about how long the oldest person ever lived). If you think of life span in any of these ways, then it is very different from life expectancy. Say the life expectancy (from birth or some older age) is 40 years. If you went to a place like this you might find plenty of old people over 70 or so, because 40 is the average age of death, not the actual age of death.

The statement “I’m 40 years old. If this was the Paleolithic I’d be dead by now” belies the confusion between lifespan and life expectancy, but it also, along with other statements of fact about “The Paleolithic” demonstrates widespread misconceptions about the past. (Another clue here is the use of the word “the” … the definite article signifying a lack of variation or diversity in that to which it refers … the “Paleolithic.”)

Consider the following estimates of female life expectancy in the US from Age 10:

1850: 47.2
1920: 55.17
1990: 70.1
2004: 71.3

These data (source)indicate a dramatic change over time, and might be used as the basis for a statement like “If this was antebellum US, and I was 50, I’d be dead by now.” Also, we see what might be a steady increase in life expectancy from the “old days” (1850) to modern times, with not a lot of change after that. Perhaps the Paleolithic ened around 1940 or so.

One reasonable estimate for life expectancy during the “Paleolithic” might be derived from estimating life expectancy for modern day foragers. It would be more convincing if life expectancy estimates did not vary a lot among modern foragers living in a diversity of environments (suggesting that the estimate is robust). This is in fact the case. Life expectancy of forager females at age of 15 in four different groups living in the New World and Old World, and arid vs rain forest conditions, range from about 52 to 58 years¹. So now we see that the “Past” (1850) for US females was perhaps more brutal than the “Past” for our species in general, the former having a much shorter life expectancy prior to the Civil War. (I know: I’m comparing 15 years to 10 years of age, but if we switched from 10 to 20 for the US data the situation would become much more gruesome, and I don’t have data for age 15.)

Human forager females, according to the same data, tend to experience their last reproductive event between 37 and 42 years of age, leaving several years, on average, between having the last child and being unable to care for that child because of one’s own death. Early anthropologists assumed that this made sense because one would want to stop reproducing in time to increase the likelihood of being able to care for offspring for a few years, but in more recent years, evolutionary biologists pointed out that mammals in general don’t do this… they just keep reproducing up until they die, which makes more sense, because it is impossible to say that a certain offspring or litter will be left motherless. So why not give it a try.

Menopause is a biological phenomenon in which women literally shut down their reproductive functioning. The idea that female mammals should keep reproduction up until a death uncertain in its timing may make a lot of sense, but if so, menopause makes no sense. Menopause is not a common phenomenon among mammals: Only a few species have been shown to have a post-reproductive life stage in females. The total number of species in which it has been observed is probably fewer than a dozen. The total number of species in which it has been observed in the wild, and can’t be explained as a function of captivity, is probably two or three (humans included).

The average age of menopause is about 42-58 years of age. If among foragers the average age of death is about 55, and the average age of last reproduction is about 40, and the average age of menopause is between these to dates, than it is possible that menopause is actually an evolved loss of reproductive function. This has been proposed and explained as older females shifting their efforts from reproduction to foraging on behalf of their offspring (and their offspring’s offspring)¹ and in particular, foraging for plant underground storage organs, which are believed to be fallback foods very important in human evolutionary history²

What does all this have to do with falsehoods and lifespans? This: If menopause really is an adaptation facilitating the use of plant underground storage organs by humans, and it happens late in the life of human females, say around the age of forty-something, then this means that there is an entire life-history stage (infancy, childhood, adolescence, young adulthood, middle age, MENOPAUSE, death) that happens AFTER you falsely assume you would be dead had you lived in the “Palaeolithic.” The Palaeolithic … when this adaptation emerged. So now you know why I cringe when I hear people say that.

So, yeah, sure, life expectancy has gone up, both because the babies don’t die as much and because we have amazing pharmaceuticals and other medical things to reduce death rates all along a person’s life history and to extend death of the elderly well beyond what would happen either in a Paleolithic setting where everyone would have been eaten by a sabertooth cat on their 40th birthday or a post-Palaeolithic setting where everyone would die of hardening of the arteries much later in life. But much of that modern medical-caused variation in life expectancy is post-menopause onset.

Then there is the issue of variation in the past (and present). Simply put, it is not the case that there was A Palaeolithic and A Now. There was a lot of variation in the past, and there is a lot of variation in the present. Many things thought of as having trends in one direction did not. For instance, in many areas, when agriculture was introduced the overall health of the population with this new technology and diet seems to have gone down. Life expectancy probably went down, rate of infections disease may have gone up, various diet-related problems like anemia may have become common, and periods of starvation that often accompany lack of food diversity linked to seasonally rigid high-labor agricultural efforts may have occurred. In some areas where this has been archaeologically documented, things later improved, presumably as a combination of both genetic and cultural adaptations to a new kind of food stress.

The reason this is important is that simplifications of the past (or for that matter, the present) is often associated with a false belief in certain causalities. We live in a “modern” world with certain features, including agriculture, industrial production of goods, lots of time spent on education, and Smart Phones. We have a longer life expectancy. Therefore, Smart Phones, our industrialized world, agriculture, etc. gave us our longer life spans. It’s all good.

The problem is that it isn’t all so simple and it isn’t all so good. Adding agriculture caused disease and death and suffering and other bad stuff. More recently, adding industry does the same thing but worse. Of course, you realize that your Smart Phone and your running shoes and your other cool stuff probably do not affect your life expectancy much, but you must also know that it does affect other people’s life expectancy, and usually negatively. Those people working in the sweat shops in China and Indonesia making your stuff don’t just get underpaid for their hard work. They die younger. The US based women with the lowish life expectancy mentioned above included women working very hard on farms and cranking out unusually large number of babies (and that will kill you) and women working in industrial sweatshops (that can kill you too). The Industrial revolution in the US was not an improvement, overall, for anybody or anything except those who got rich off it.

Humans do not live on a one-way street with two addresses: “Then” (not so good) and “Now” (improved in all ways) and life expectancy is not a variable that maps our movement from a nasty brutish and short-lived past to an all round better present with no stops or turns along the way. The big recent increase in life expectancy notwithstanding, various different populations of humans have experienced numerous shifts in health and well being, some tracked by expected age of death for various cohorts.

¹Kaplan, H, K. Hill, J. Lancaster, A. M. Hurtado. 2000. A theory of human life history evolution: Diet, intelligence, and longevity. Evolutionary Anthropology 9:156-185, 2000.

²Laden, G. and R. Wrangham. The rise of hominids as an adaptive shift in fallback foods. Journal of Human Evolution. (pdf

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