Child mortality in foraging tribes was severe — sometimes on purpose:
The prevalence of infanticide varied significantly among foraging tribes. It was as high as 30% of children in traditional artic tribes (in the early 1900s), and zero in others, with an average infanticide rate of 21% among the cross-culture sample of tribes anthropologists measured. In some cultures infanticide was biased towards females, perhaps to balance gender ratios, particularly in tribes where men contributed more food to the family than women (which was not the norm). In other tribes infanticide was practiced to space births, as Robert Kelley says, “in order to maximize reproductive success, rather than population control.” In nomadic cultures mothers needed to carry not only their tools and household items, but also their small children. On frequent long migrations to find food a family had to carry all their possessions. For a pregnant woman to carry more than one small child would endangered the older sibling. Better for all to have children spaced apart.Child mortality in foraging tribes was severe. A survey of 25 hunter-gatherer tribes in historical times from various continents revealed that on average 25% of children died before they were one, and 37% died before they were 15. In one traditional hunter-gather tribe child mortality was found to be 60%. Most historical tribes have a population growth rate of approximately zero. This depression is made evident, says Robert Kelley in his survey of hunter-gathering peoples, because “when formerly mobile people become sedentary, the rate of population growth increases.” All things equal, the constancy of farmed food breeds more people.
While many children died young, hunting-gather elders did not have it much better. There are no known remains of a Neanderthal who lived to be older than 40. Because extremely high child mortality rates depress average life expectancy, if the outlier oldest is only 40, the median age of a Neanderthal was less than 20. It was a tough life. Based on an analysis of bone stress and cuts, one archeologist said the distribution of injuries on the bodies of Neanderthal were similar to those found on rodeo professionals — lots of head, trunk and arm injuries like the ones you might get from close encounters with large angry animals. Erik Trinkaus discovered that the pattern of age-related mortality for hunter-gatherers and Neanderthal were nearly parallel, except historical foragers lived a little longer.
A typical tribe of hunters-gatherers had few very young children and no old people. This demographic may explain a common impression visitors had upon meeting intact historical hunter-gatherer tribes. They would remark that “everyone looked extremely healthy and robust.” That’s in part because most everyone was in the prime of life between 15 and 35. We might have the same reaction visiting a city or trendy neighborhood with the same youthful demographic. We’d call them young adults. Tribal life was a lifestyle for and of young adults.