CHAPTER FOURTEEN
The Longevity Lie (Short?)
The days of our years are threescore years and ten; and if by reason of strength they be fourscore years, yet is their strength labor and sorrow; for it is soon cut off, and we fly away.
PSALMS 90:10
Strange but true: The average height expectancy of prehistoric humans was about three feet, so a four-foot tall man was considered a giant.
Does that fact alter your image of prehistory? Are you picturing a diminutive race of bonsai people living in mini-caves, chasing rabbits into holes, cowering in fear of foxes, being carried off by hawks? Does this cause you to rethink what a challenge a mammoth hunt must have been for our half-pint ancestors? Does it make you feel even luckier to be living today, when our superior diet and sanitation have doubled the average person’s height expectancy?
Well, don’t get carried away. While it is technically true that the average “height expectancy” of prehistoric men was about three feet, it’s a misleading sort of truth. Like overconfident declarations about the universality of marriage, poverty, and war, it’s the sort of assertion that sows confusion and results in a harvest of misleading data.
Take the average height of a full-grown man living in prehistoric times (using skeletal remains as a guide): about six feet tall (72 inches). Then take the average size of a prehistoric infant’s skeleton (let’s say about 20 inches). Then extrapolate from the ratio of infant-to-adult skeletons at known archaeological burial sites and presume that in general, for every three people who lived to adulthood, seven died as infants. Thus, owing to the high rate of infant mortality, average human height in prehistory was (3 × 72) + (7 × 20) ÷ 10 = 35.6 inches. Roughly three feet.1
Absurd? Yes. Misleading? Yup. Statistically accurate? Well, kinda.
This height expectancy “truth” is no more absurd or misleading than what most people are led to believe about human life expectancy in prehistory.
Exhibit A: In an interview with NBC Nightly News,2 UCSF bio-physicist Jeff Lotz was discussing the prevalence of chronic back pain in the United States. The millions of people watching that night heard him explain, “It wasn’t until two or three hundred years ago that we lived past age forty-five, so our spines really haven’t evolved to the point where they can maintain this upright posture with these large gravity loads for the duration of our lives [emphasis added].”
Exhibit B: In an otherwise solid book about women in prehistory (The Invisible Sex), an archaeologist, an anthropologist, and an editor of one of the world’s leading science magazines team up to imagine the life of a typical woman they call Ursula, living in Europe 45,000 years ago. “Life was hard,” they write, “and many, especially the young
and the old, died of starvation in winter and accidents of one sort or another, as well as disease…. Ursula [having had her first daughter at age fifteen] lived long enough to see her first granddaughter, dying at the ripe old age of 37 [emphasis added].”3
Exhibit C: In a New York Times article,4 James Vaupel, director of the laboratory of survival and longevity at the Max Planck Institute for Demographic Research, explains, “There is no fixed life span.” Dr. Vaupel points to the increase in life expectancy from 1840 to today in countries where the figure is rising quickest and notes that this increase is “linear, absolutely linear, with no evidence of any decline or tapering off.” From this, he concludes, “There’s no reason that life expectancy can’t continue to go up two to three years per decade.”
Except that there is. At some point, all the babies who can survive to adulthood, do. Further advances will be slight.
When Does Life Begin? When Does It End?
The preceding numbers are just as fantastical as the ones we came up with for our average height expectancy estimate. They are, in fact, based upon the same erroneous calculation distorted by high infant mortality rates. When this factor is eliminated, we see that prehistoric humans who survived beyond childhood typically lived from sixty-six to ninety-one years, with higher levels of overall health and mobility than we find in most Western societies today.
It’s a game of averages, you see. While it’s true that many infants and small children died in prehistoric populations—as indicated by the larger numbers of infant skeletons in most burial sites—these skeletons tell us nothing about what constituted a “ripe old age.” Life expectancy at birth, which is the measure generally cited, is far from an accurate measure of the typical life span. When you read, “At the beginning of the 20th century, life expectancy at birth was around 45 years. It has risen to about 75 thanks to the advent of antibiotics and public health measures that allow people to survive or avoid infectious diseases,”5 keep in mind that this dramatic increase is much more a reflection of increased infant survival than of adults living longer.
In Mozambique, where one of us was born and raised, the average life expectancy at birth for a man is currently, tragically, about forty-two years. But Cacilda’s father was ninety-three when he died, riding his bicycle right to the end of the road. He was old. A forty-year-old is not. Not even in Mozambique.
No doubt, many prehistoric infants died from disease or harsh conditions, as do the infants of other primates, human foragers, and modern Mozambiqueans. But many anthropologists agree it’s likely that a large portion of infant mortality once attributed to starvation and disease probably resulted from infanticide. They argue that foraging societies limited the number of infants so they wouldn’t become a burden to the group or allow overly rapid population growth to strain food supplies.
Horrific as it may be for us to contemplate, infanticide is anything but a rarity, even today. Anthropologist Nancy Scheper-Hughes studied contemporary infant deaths in northeast Brazil, where about 20 percent of infants die in their first year. She found that women consider the deaths of some children a “blessing” if the babies were lethargic and passive. Mothers told Scheper-Hughes they were “children who wanted to die, whose will to live was not sufficiently strong or developed.” Scheper-Hughes found that these children received less food and medical attention than their more vigorous siblings.6
Joseph Birdsell, one of the world’s greatest scholars of Australian Aboriginal culture, estimated that as many as half of all infants were intentionally destroyed. Various surveys of contemporary pre-industrial societies conclude that anywhere from half to three-quarters of them practice some form of direct infanticide.
Lest we start feeling too smug in our compassion and superiority, recall the foundling hospitals of Europe. The number of babies delivered to near-certain death in France rose from 40,000 in 1784 to almost 140,000 by 1822. By 1830, there were 270 revolving boxes in French foundling hospital doors specially designed to protect the anonymity of those depositing unwanted infants. Eighty to 90 percent of these children are estimated to have died within a year of arrival.
Once our ancestors began cultivating land for food, they were running on a wheel, but never fast enough. More land provides more food. And more food means more children born and fed. More children provide more help on the farm and more soldiers. But this population growth creates demand for more land, which can be won and held only through conquest and war. Put another way, the shift to agriculture was accelerated by the seemingly irrefutable belief that it’s better to take strangers’ land (killing them if necessary) than to allow one’s own children to die of starvation.
Closer to our own time, the BBC reports that as many as 15 percent of the reported deaths of female infants in parts of southern India are victims of infanticide. Millions more die in China, where female infanticide is prevalent, and has been for centuries. A late nineteenth-century missionary living in China reported that of 183 sons and 175 daughters born in a typical community, 126 of the sons lived to age ten (69 percent), while only 53 of the daughters made it that far (30 percent).7 China’s one-child policy, combined with the cultural preference for sons, has only worsened the already dismal odds of survival for female infants.8
There are also problematic cultural assumptions lurking within demographers’ calculations, in which life is assumed to begin at birth. This view is far from universal. Societies that practice infanticide don’t consider newborn infants full human beings. Rituals ranging from baptism to naming ceremonies are delayed until it is determined whether or not the child will be permitted to live. If not, from this perspective, the child was never fully alive anyway.9