The sex ratio at birth - Historical aspects

This paper reviews the classical theories that attempted to explain the influences on the sex ratio at birth (M/F). These included notions pertaining to the four elements (earth, air, fire and water) and to laterality i.e. from which side of the body (in both parents) the conceptual principle arose. This narrative will also outline the initial physical measurements of male and female births and speculations by John Graunt (1620-1674), John Arbuthnott (1667-1735) and Johann Süssmilch (1707-1767), as well as the conundrums that M/F presented to Charles Darwin (1809-1882) and the theories of Ronald Fisher (1890-1962) who expanded on concepts first promulgated by Nicolas de Caritat, Marquis de Condorcet (1743-1794). Fortunately, the thousands of papers generated on topic, especially the more recent work pertaining to direct and measurable influences (such as exogenous stress periconceptually and during pregnancy) have begun to yield some concrete findings, indeed, "among this welter of evidence, it is possible to pin down a few facts" such that "we have found ourselves following Ariadne's thread to a series of clues that bind the calculation of the proportion of boys and girls at birth".