Exploring the Variations of the Sex Ratio at Birth from an Historical Perspective

Abstract

Variations in sex ratios at birth is still an active research field and several studies in the last decades have focused on this topic. In this article, studies on the main determinant of long- and short-term trends are briefly reviewed, taking into account findings and results from different kinds of disciplines. In his early studies, Corrado Gini concluded that the human sex ratio at birth was universally stable, without significant fluctuations across time and space. However, in the last decades several authors have directly challenged these conclusions. Therefore, after summarizing the results of Gini’s research on the historical trends of the sex ratio at birth, a brief review focuses on the analyses of contemporary trends. The main determinants of the variations of the sex ratio at birth in time and space mentioned in the literature and the corresponding theoretical explanations are summarized. Special attention is paid to the recent studies on the impact of the environment, pollution and climate on the levels of sex ratio at birth.