in an adult sex ratio of 136 males for every 100 females. Cowgill theorised that this was partly because girls were more likely to be victims of infanticide, and partly because sons tended to receive better feeding and care than daughters. In Guatemala, Cowgill studied an indigenous village where the sex ratio was even more skewed—178:100. Cowgill observed that mothers in this village breastfed sons for much longer than daughters, and tended to give them preferential treatment even after weaning. Cowgill and Hutchinson also speculated that the sexually provocative behaviour of young girls in this village might be a survival mechanism. Seasons of birth Cowgill undertook one of the first scientific studies of seasonality in human reproduction. Taking data from historical records and indigenous peoples in various countries, she concluded that conception and birth in human beings, like that of many other animals, followed seasonal patterns to a degree. Because the pattern was different in the Northern and Southern Hemispheres, Cowgill hypothesised that weather was the determining factor. However, she found that in urbanised and industrialised areas the pattern had been disrupted. Her 1966 article on the topic, published in the journal Ecology, has formed the basis for subsequent research by other scientists. Selenium and AIDS In 1997, Cowgill gauged the selenium content of soil in various locations in the United States by measuring the amount of the mineral that was absorbed by alfalfa. She then correlated this information with the mortality rate of AIDS in the area. She found that the more selenium there was in the soil, the lower mortality from AIDS was. The relationship was especially strong among African-Americans. Publications Bajo de Santa Fe (with G.E. Hutchinson). Book, 1963. The history of Laguna de Petenxil, a small lake in Northern Guatemala. Book, 1966. Aquatic toxicology and hazard assessment, 12th volume (with Llewellyn R. Williams). Book, 1989. References External links 1927 births 2015 deaths American biologists American anthropologists American women anthropologists American Mesoamericanists Women Mesoamericanists Mesoamerican anthropologists American women biologists Women primatologists Primatologists 20th-century Mesoamericanists Iowa State University alumni American Civil Liberties Union people 20th-century American women scientists 20th-century American scientists 21st-century American women