On the Mathematics of Fraternal Birth Order Effect and the Genetics of Homosexuality

TL;DR

This paper explores the mathematical relationship between the fraternal birth order effect and the genetics of homosexuality, revealing how these phenomena are interconnected through maternal fecundity and sibling dynamics.

Contribution

It provides a mathematical framework linking the fraternal birth order effect with genetic factors influencing homosexuality, highlighting their mutual implications.

Findings

Fraternal birth order effect correlates with maternal fecundity.

Homosexuality is mathematically linked to increased maternal fecundity.

The probability of younger brothers being homosexual increases with maternal fecundity.

Abstract

Mathematicians have always been attracted to the field of genetics. I am especially interested in the mathematical aspects of research on homosexuality. Certain studies show that male homosexuality may have a genetic component that is correlated with female fertility. Other studies show the existence of the fraternal birth order effect, that is the correlation of homosexuality with the number of older brothers. This paper is devoted to the mathematical aspects of how these two phenomena are interconnected. In particular, I show that the fraternal birth order effect produces a correlation between homosexuality and maternal fecundity. Vice versa, I show that the correlation between homosexuality and female fecundity implies the increase of the probability of the younger brothers being homosexual.