This is not conclusive evidence that fertility has been reduced in these men, say the research team, but certainly should lead to further investigation.

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He added that if men could improve their fertility through avoiding hot baths, couples may be able to avoid IVF or choose less invasive treatment.

BBC: Last Updated: Monday, 5 March 2007, 11:20 GMT

He added it appeared that the authors had not compared their sperm data and fertility rates with those of infertile men with varicoceles who did not have the embolisation procedure.

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Unlike women, men do not have their fertility cut off suddenly.

ECONOMIST: Evolutionary biology

The ritual ceremony of the Voladores ('flying men') is a fertility dance performed by several ethnic groups in Mexico and Central America, especially the Totonac people in the eastern state of Veracruz, to express respect for and harmony with the natural and spiritual worlds.

UNESCO: Culture

The researchers say their findings are not conclusive but suggest that men who want to improve their fertility might want to look at increasing the amount of physical exercise they do if they currently do little.

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Researchers examined semen samples provided by men aged between 18-70 whose partners were undergoing fertility treatment because of blocked or missing fallopian tubes.

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Studies showed that during periods of high fertility, women are more drawn to more rugged, dominant-looking men.

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At the University of Sheffield, where Mossman did his doctoral studies, he and his co-authors measured the heads, midpieces, and flagella of 30 sperm per man, from 103 men randomly selected from a pool of about 500 who were recruited for a larger fertility study.

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