By Jane Nambi

According to a study done by ecologist Dr. Samuli Helle of the University of Turku in Finland and Dr. Virpi Lummaa of the University of Sheffield in the United Kingdom, having more sons reduces life of a woman than when she gives birth to girls.

The study was carried out on women born during the 17th to the 20th centuries in different parts of Finland. The researchers concluded that a woman who gave birth to six sons lived, on average, 32.4 years after the birth of the youngest son as compared to the 33.1 lived by one who bore girls of the same number.

“Irrespective of access to resources, mothers, but not fathers, with many sons suffered from reduced post-reproductive survival,” they wrote in the study. This does not discriminate in terms of social or financial status of the family. “Adult sons may be beneficial for their parental well-being and thus survival in some countries, but girls may be beneficial in other countries,” he said.

Helle said in a statement, “The research shows the more sons you have the lower post-reproductive survival was. Biologically, there is a bigger cost associated with having a boy than a girl, so that is one explanation for the shorter lifespan.” Male babies are usually bigger than female babies, which may have meant that they required more nutrients from the mother’s body during gestation, researchers suggest.

Although there is a link between having sons and dying earlier, the research fails to show the connection between the two. “One could speculate that owing to modern medical care, smaller family size and more abundant resources, the biological costs of reproduction might not play that important role in modern societies anymore,” Helle said.