The life expectancy myth, and why many ancient humans lived long healthy lives
It is not uncommon to hear talk about how lucky we are to live in this age of scientific and medical advancement where antibiotics and vaccinations keep us living longer, while our poor ancient ancestors were lucky to live past the age of 35. Well this is not quite true. At best, it oversimplifies a complex issue, and at worst it is a blatant misrepresentation of statistics. Did ancient humans really just drop dead as they were entering their prime, or did some live long enough to see a wrinkle on their face?
According to historical mortality levels from the Encyclopaedia of Population (2003), average life expectancy for prehistoric humans was estimated at just 20 – 35 years; in Sweden in the 1750s it was 36 years; it hit 48 years by the 1900s in the USA; and in 2007 in Japan, average life expectancy was 83 years. It would appear that as time went on, conditions improved and so did the length of people’s lives. But it is not so simple.
What is commonly known as ‘average life expectancy’ is technically ‘life expectancy at birth’. In other words, it is the average number of years that a newborn baby can expect to live in a given society at a given time. But life expectancy at birth is an unhelpful statistic if the goal is to compare the health and longevity of adults. That is because a major determinant of life expectancy at birth is the child mortality rate which, in our ancient past, was extremely high, and this skews the life expectancy rate dramatically downward.
The early years from infancy through to about 15 was perilous, due to risks posed by disease, injuries, and accidents. But those who survived this hazardous period of life could well make it into old age.
Drawing upon archaeological records, we can indeed see evidence of this. The "Old Man of La Chapelle", for example, is the name given to the remains of a Neanderthal who lived 56,000 years ago, found buried in the limestone bedrock of a small cave near La Chapelle-aux-Saints, in France in 1908. Scientists estimate that he had reached old age by the time he died, as bone had re-grown along the gums where he had lost several teeth, perhaps decades before. He lacked so many teeth in fact that scientists suspect he needed his food ground down before he was able to eat it. The old man's skeleton indicates that he also suffered from a number of afflictions, including arthritis.
Facial reconstruction from the skull of ‘The Old Man of La Chapelle’. Photo source .
If we look again at the estimated maximum life expectancy for prehistoric humans, which is 35 years, we can see that this does not mean that the average person living at this time died at the age of 35. Rather, it means that for every child that died in infancy, another person might have lived to be 70. The life expectancy statistic is, therefore, a deeply flawed way to think about the quality of life of our ancient ancestors.
So is modern society more beneficial for health and longevity than, say, the hunter-gatherer lifestyle? To help gain an answer to this question, scientists have compared the life span of adults in contemporary hunter-gatherer tribes (excluding the infant mortality rate). It was found that once infant mortality rates were removed, life span was calculated to between 70 and 80 years, the same rate as that found in contemporary industrialised societies. The difference is that, in the latter, most individuals survive childhood (Kanazawa, 2008).
It is certainly true that improvements in food availability, hygiene, nursing care, medical treatments, and cultural innovations have resulted in far fewer deaths caused by external injuries, infections, and epidemics, but on the other hand, we face a global cancer crisis that our ancient ancestors never had to contend with on such a scale. Are we just replacing one form of death with another?
A summary of major causes of death over time. S. Horiuchi, in United NaEons, Health and Mortality: Issues of Global Concern, 1999
Archaeologists and anthropologists face a real challenge in trying to unravel reliable information about the age structure of ancient populations, largely due to the lack of a sufficient number ancient samples, as well as the difficulties in determining exact age. Nevertheless, we can safely say that our ancient ancestors were not dropping dead at 35, and some would have even been blessed with long and healthy lives.
Featured image: Reconstruction of a Neanderthal in the Neanderthal Museum, Mettmann, Germany.