If A Man Has Brothers...He Has Better Sperm

If A Man Has Brothers...He Has Better Sperm

A new study from Sheffield University has found that if you are a male with more brothers than sisters, then your sperm will have increased swimming abilities, and be more likely to fertilise an egg.

Scientists from Sheffield University collaborated with researchers at Brown University in America, and found a correlation between the speed of a man's sperm, and the number of brothers he has.

The findings were published on the Asian Journal of Andrology website, and supported previous study results that parents with genes for good male fertility are more likely to have boys.

The Senior Lecturer in Andrology at Sheffield University, Dr Allan Pacey, said "The results are very surprising and could provide genetic insights into why some men are more fertile than others, but at the moment have no clinical relevance to how we might manage and treat male fertility. It does however, give food for thought about the importance of genetics for sperm motility and may open the way to more studies in this area".

The team used high level technology to analyse the sperm of over 500 men. They accurately measured how fast the men's sperm swam, and then reviewed how many brothers or sisters he had.
Upon reviewing their findings, they discovered that the men with more brothers rather than sisters had faster swimming sperm.

The team did not conclude that siblings directly influence fertility, but they did say there was a distinct correlation that could not be ignored.
Dr Jim Mossman, a researcher at Brown University said, "This is certainly not a smoking gun as a reason for infertility in men. However it would be interesting to test whether the same relationships are observed in other human populations as well as in other species. Likewise, would we observe similar associations when looking at female fertility? If the relationship between sex-bias in the number of children and fertility is a more universal phenomenon, then we may expect female fertility to follow a similar pattern, albeit in the opposite direction".

Professor of Evolutionary Genetics at Sheffield University, Jon Slate, has said "We are very intrigued by this finding and hope other researchers examine their datasets in a similar fashion. If our results can be replicated we think it provides some evidence that humans have experienced what evolutionary biologists like to call 'sexual conflict' ".
He went on to say "The idea behind this is that genes that make males reproductively successful make females reproductively unsuccessful and vice versa".

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