Starting and bringing up a family can cost parents dearly, however, some reproductive events work out costing a great deal more than others, according to an article published in Proceedings of the Royal Society B. Biological Sciences.

Previous studies have demonstrated that having sons can reduce the lifespan of the mother – this higher cost can also be passed on to her other children.

Ian Richard, Department of Animal and Plant Sciences, University of Sheffield, UK, and team used a pedigree dataset from pre-industrial Finland and investigated whether humans who had elder brothers had different lifespans and reproductive success, compared to those who had elder sisters.

The researchers found that individuals who had older brothers raised 27% fewer children compared to those with older sisters. This difference was due to the number of children produced during adulthood, not because of any difference in survival, the authors wrote.

The authors concluded that a mother’s reproductive history, whether she has sons or daughter, may have long-term consequences for her children.

“Producing sons reduces lifetime reproductive success of subsequent offspring in pre-industrial Finns”
Ian Rickard; Andrew Russell; Virpi Lummaa
Proceedings of the Royal Society B: Biological Sciences
DOI10.1098/rspb.2007.1051
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Written by: Christian Nordqvist