My family has a disproportionate number of males. I have two brothers and a sister. My dad had three brothers and a sister. My cousins on my dad’s side are comprised of six males and two females. On my mom’s side things are a bit more even-she had a sister and a brother, and my cousins are composed of a male and a female.

Learning about genetics in high school, I wondered if there might be a genetic reason for the tendency of children born on my dad’s side of my family to be male. However my teachers, perhaps for the sake of simplifying the lessons told me that because the geneder of the child was determined by the contribution of a X chromosome from the mother and a X or Y chromosome from the father, the odds of a child being male or female had to be fifty percent. I accepted their answer, even if it made no sense based on experience. If I had been smarter, I might have wondered, like a research group at Newcastle University which recently published a paper, if there might be some influence on whether a father was more likely contribute an X or Y chromosome, which would in turn lead to a gender disparity.

The recent research done by the group at Newcastle University suggests that there may be a connection between the gender ratio of children on the father’s side and the gender ratio of those children’s children. After studying thousands of family trees, the group suggests that a gene passed on by the father influences whether a son will have more sons or daughters. Sons who come from families with more males are more likely to have male children, while a daughter from a family with only sisters who marries a man with only sisters is more likely to have daughters than sons. The group notes that this gene could also explain why more males than females are born after wars-families with more males are more likely to have surviving sons than those with few.

You can read more about this in a press release from Science Daily.