Socioeconomic status influences sex ratios in a Chinese rural population

Abstract

According to the logic of the Trivers-Willard hypothesis, in a human population, if socioeconomic status is transmitted across generations to some extent, and if sons of high-status parents tend to have higher reproductive success than daughters, while daughters of low-status parents tend to have higher reproductive success than sons, then we should expect that offspring sex ratio is positively associated with socioeconomic status. This study examines whether the assumptions and prediction of this hypothesis apply to a rural population in northern China. Results show that (1) current family socioeconomic status is positively related to family head's father's socioeconomic status in around 1950, (2) low-status family heads have more grandchildren through their daughters than their sons, whereas high- or middle-status family heads have more grandchildren through sons, and (3) as family heads' status increases, they tend to produce a higher offspring sex ratio. Therefore, the assumptions and prediction of the hypothesis are met in the study population. These results are discussed in reference to past studies on sex ratio manipulation among humans.

Keywords: Offspring sex ratio; Peasants; Socioeconomic status; Trivers–Willard hypothesis.

Figure 1. Number of sons’ children and daughters’ children by family socioeconomic status, showing mean ± 1 SE.

Figure 2. Offspring sex ratio by family socioeconomic status, showing mean ± 1 SE.

Figure 3. Offspring sex ratio by number of children for family heads with low, middle, or high family socioeconomic status, showing mean ± 1 SE.