New Study Challenges 50-50 Myth: Children's Biological Sex Not Always Random

Same-sex siblings: More than mere coincidence?

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Does parental age factor in?

Genetics: A new frontier?

Contrasting views from the scientific community

A new study is challenging the traditional belief that the sex of a child is a 50-50 genetic lottery between X and Y chromosomes. Research published in Science Advances suggests that individual families may have skewed odds toward consistently having either boys or girls, influenced by factors such as age, genetics, and the environment.

Led by epidemiologist Dr. Jorge Chavarro of Harvard T.H. Chan School of Public Health, the study analyzed data from the historic Nurses’ Health Study, examining over 58,000 pregnancies between 1956 and 2015. While the general population showed an even split between male and female births, some families appeared more likely to have children of the same sex, contrary to random chance.

Approximately one in three families in the study had children all of the same sex, a figure higher than expected by probability theory, especially in families with three or more kids. The researchers suggested that each couple might have a unique probability of producing a child of one sex or the other, impacting outcomes within families.

The study also found that women who had their first child later in life showed a stronger effect, indicating possible biological shifts over time that could influence the likelihood of having children of the same sex. Genetic loci linked to this phenomenon were identified, hinting at a potential genetic influence on sex bias.

While the findings are intriguing, they are not without controversy. Some experts remain skeptical, citing the need for more diverse cohorts to draw broader conclusions. This study opens new avenues for genetic and evolutionary research on how heritable factors interact with environmental variables to influence offspring sex.

For couples with multiple same-sex children or those seeking variety, this research offers insight and raises questions about the future of reproductive biology. It prompts discussions on the potential implications for fertility treatments and genetic interventions to balance the family tree.

According to the source: The Economic Times.