Big Brother Is ... Stealing Your Fertility

Having an older bro reduces your odds of having kids, study finds
By Kevin Spak,  Newser Staff
Posted Nov 19, 2008 2:55 PM CST
Big Brother Is ... Stealing Your Fertility
A girl smiles at her big brother, unaware that he has diminished her chance of having children.   (Shutterstock)

If you have an older brother, odds are slightly greater you won’t be having kids, especially if you live in pre-industrial Finland. According to a new study, which examined the birth, marriage, and death records of three generations of pre-industrial Finlanders, found that those with older brothers were 5% less likely to become parents than those with older sisters.

That disparity applied to both men and women, which researchers believe indicates that the disparity has a biological basis rather than simply a cultural one. It’s possible the stress of carrying a boy damages a woman’s womb, slightly affecting the next child’s health. Those effects could be “spread over a variety of physiological systems,” they said. A previous study, for example, shows that children with older brothers tend to be shorter. (More study stories.)

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