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Old 02-02-2009, 05:54 AM   #1
Darryl Shaw
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Join Date: Apr 2008
Posts: 681
Default Longevity among hunter-gatherers: a cross-cultural examination.

This is quite a long read but it shows that the average lifespan of hunter-gatherers isn't quite as short as you might expect, indeed as table 4 shows average lifespans are only slightly shorter than the average for the U.S. and, presumably, other developed countries.

Degenerative deaths are relatively few, confined largely to problems early in infancy and late-age cerebrovascular problems, as well as attributions of "old age" in the absence of obvious symptoms or pathology. Heart attacks and strokes appear rare and do not account for these old-age deaths (see Eaton, Konner, and Shostak 1988), which tend to occur when sleeping. It has often been remarked that few risk factors for cardiovascular disease exist among active members of small-scale societies (Eaton et al. 1994), although compromised lung or kidney functioning can interact with cardiac fibrosis or moderate arterial stenosis to cause cardiac arrest. Obesity is rare, hypertension is low, cholesterol and triglyceride levels are low, and maximal oxygen uptake is high. Overall, degenerative disease accounts for 6-24 percent (average 9 percent) of deaths, with the highest representation among Northern Territory Aborigines. Neoplasms and heart disease each accounted for 9 of the 42 deaths due to degenerative illness. It should be pointed out, however, that chronic illnesses as causes of death are the most difficult to identify, since more proximate causes are likely to be mentioned. To our knowledge there have been no focused studies or mention of Alzheimer's, Parkinson's, or other forms of dementia.
Summary of results

We summarize our main findings to this point:

Post-reproductive longevity is a robust feature of hunter-gatherers and of the life cycle of Homo sapiens. Survivorship to grandparental age is achieved by over two-thirds of people who reach sexual maturity and can last an average of 20 years.

Adult mortality appears to be characterized by two stages. Mortality rates remain stable and fairly low at around 1 percent per year from the age of maturity until around age 40. After age 40, the rate of mortality increase is exponential (Gompertz) with a mortality rate doubling time of about 6-9 years. The two decades without detectable senescence in early and mid-adulthood appear to be an important component of human life span extension.

The average modal age of adult death for hunter-gatherers is 72 with a range of 68-78 years. This range appears to be the closest functional equivalent of an "adaptive" human life span.

Departures from this general pattern in published estimates of life expectancy in past populations (e.g., low child and high adult mortality) are most likely due to a combination of high levels of contact-related infectious disease, excessive violence or homicide, and methodological problems that lead to poor age estimates of older individuals and inappropriate use of model life tables for deriving demographic estimates.

Illnesses account for 70 percent, violence and accidents for 20 percent, and degenerative diseases for 9 percent of all deaths in our sample. Illnesses largely include infectious and gastrointestinal disease, although less than half of all deaths in our sample are from contact-related disease.

Comparisons among hunter-gatherers, acculturated hunter-gatherers, wild chimpanzees, and captive chimpanzees illustrate the interaction of improved conditions and species differences. Within species, improved conditions tend to decrease mortality rates at all ages, with a diminishing effect at older ages. Human and chimpanzee mortality diverge dramatically at older ages, revealing selection for a longer adult period in humans.

EDIT: I found the original pdf which contains a number of tables and graphs not included in the above link.

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