Population Structures of Ghanzi and Ngamiland !Kung

American J Phys Anthropol

Harpending

1988

Self Cite

111

In this paper we develop a model that examines fertility and childhood mortality patterns and their relationship to environmental variables. Interactions among environmental variables can account for different fertility patterns and different mixes of these variables can produce similar patterns of fertility. Our model attempts to quantify the idea that there is a trade-off between producing a few children likely to survive to reproductive age and producing a greater number of children with lower chances for survival. The optimum mix of these strategies depends on environmental characteristics. We use the model to make predictions about fertility and mortality patterns among two Bushmen populations of southern Africa--the Ghanzi and Ngamiland !Kung--using data collected by Harpending in 1967-1968. The results do not support explanations of the low fertilities observed among !Kung Bushmen women, in whom it is thought that fitness is maximized by limiting fertility, and show no relationship between mortality and family size in either !Kung population. Instead, the number of offspring reaching reproductive age in both populations increases as their completed family size increases. We examine the effects of sex, birth order, and paternal investment on mortality. No sex ratio differences and no differences in mortality by sex or birth order are present. Infant mortality among women who married more than once is significantly higher than among women who married once, suggesting that paternal care has a significant effect.

Section: Resultssupporting

confidence: 93%

Section: Discussionmentioning

confidence: 77%

Section: Discussionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 97%

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Fitness and fertility among kalahari !Kung

American J Phys Anthropol

Harpending

1988

Self Cite

111

“…The frequency of various women (those age li 45 years or more in the most fre uent. T K e distribution appears to be bimoda 4 , however, with a smaller peak population tends to be associated wit i (Howell, 1979) and 4.0 (Harpending and Wandsnider, 1982). Outside of Africa, completed family sizes as low as those found among Herero have been noted in horticultural foraging o ulations such as the jeantson, 19751, who ave CFSs of 3.8 and 3.4, respectively.…”

Section: Resultsmentioning

confidence: 92%

Infertility in Herero pastoralists of southern Africa

Harpending

1991

American J Hum Biol

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Transition from low to high rates of fertility among Herero pastoralists of the northern Kalahari of Botswana is examined. Total fertility rates have increased from 2.65 in the first half of this century to 7.02 in the last decade, while postreproductive women report having had only 3.47 births. We use an indirect estimator of the fertility of mothers to show that the Herero have been afflicted with abnormally low fertility since early in this century. Although the several possible causes of subfertility in this population, including disease, maternal health, and child care practices are examined, it is concluded that the effects of venereal diseases are most likely responsible for abnormally low fertility. The dramatic increase in fertility following treatment of a major cause of infertility underscores the potential impact diseases may have on human reproductive patterns. This study is the first to document subfertility in an ethnic group of southern Africa.

Causes of early human population growth

Am. J. Phys. Anthropol.

1996

The archaeological record indicates large increases in human population coincident with the emergence of food production about 10,000 years ago. The cause of the growth is unclear. Extreme views attribute the change to increases in the birth rate or to decreases in the death rate. Many argue that sedentism led to improved ovarian function and higher fertility through higher caloric intakes or reduced activity levels. Similarly, shortened lactation periods may have reduced birth spacing and increased fertility. Others attribute the rise in population to decreases in mortality, arguing that the evidence from skeletal populations indicates improvements in health and the expectation of life at birth, though others use the same evidence to argue that mortality increased. An analysis presented here draws on findings that indicate substantial increases in the survival of young children as populations switch from nomadic to sedentary lives. Projections indicate that this improvement in child survival is so critical that it may be followed by substantially larger decreases in survival at later ages, yet result in higher population growth rates and reduced expectation of life at birth. Increases in the birth rate are not necessary for population growth, even when overall mortality increases. Large increases in overall mortality can be associated with large increases in population. Because positive population growth can occur while the expectation of life at birth declines, this analysis shows that this summary statistic is not an appropriate indicator of population fitness.