Variation in offspring sex ratio in women of differing social status

Since Trivers and Willard first postulated 15 years ago that offspring sex ratio might be adaptively manipulated by parents of mammalian species as well as hymenoptera, evidence has been accumulating in support of this hypothesis. Research suggests that female mammals are able to manipulate the secondary (birth) sex ratio of their offspring based upon their own social status and/or access to resources. This ability is thought to procure a reproductive advantage by maximizing number of grandchildren. This article reports, in further confirmation of the Trivers and Willard hypothesis, the apparent sex ratio manipulation of offspring by human females of differing social status, in a polygynous, naturally fertile population, the nineteenth-century Mormons.