Group differences in proneness to inflammation.

All humans are primarily descendants from a diaspora out of Africa approximately 50,000 years ago although there are some indications of admixture with local populations of archaic humans outside Africa. The burden of infectious disease is greater in tropical Africa than elsewhere on earth in historic times, and it was less outside Africa, especially in the New World where passage through the Beringian filter kept many Old World parasites from entering the New World with humans. As a consequence we expect that the immune system, especially susceptibility to inflammation, will be "tuned up" in people with recent tropical African ancestry, intermediate in people of European and Asian ancestry, and perhaps "tuned down" in people of Native American ancestry. We suggest that evolved responses to different pathogen burdens among geographic groups may contribute to higher rates of inflammatory disease in modern people.

Infertility in Herero pastoralists of southern Africa.

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.