Hamsters have more sperm than men

The research made by the US government shows that men now produce only about a third as much sperm as hamsters.

Scientists at Bradford University and the University of California, Berkeley, have found increased genetic damage in the sperm of men who consume average amounts of caffeine. This could lead to unsuccessful pregnancies or to children being born with deformities or genetic disease. Their research, published in the journal Human Reproduction this week.

Modern lifestyles, and exposure to chemical pollution, are blamed for a precipitous drop in sperm counts in men worldwide. A host of studies show that, on average, they have dropped by two and a half times over the past 50 years from about 150 million per millilitre of sperm fluid to about 60 million. Hamsters produce 160 million per millilitre.

And the decline is continuing. Studies by the Medical Research Council, for example,found that the fertility of Scottish men is declining by about 2 per cent a year, and that younger men are less fertile than their fathers: men in their mid thirties or younger produce a quarter less sperm than those born between 1950 and 1970.

Warming the testicles - for example by taking hot baths, wearing tight jeans, having a sedentary job or using laptops on the lap - is known to cause temporary losses in fertility, scientists say.