Falling sperm counts could cause 'extinction of the human species', warn scientists

Falling sperm counts could lead to “the extinction of the human species”, the lead author of a study into the phenomenon has warned.

Among men living in the West, sperm counts have plunged by nearly 60 per cent in just 40 years, according to a major review of scientific studies.

Dr Hagai Levine, who led the research, said if changes were not made to harmful aspects of the modern world, from unhealthy lifestyles to exposure to chemicals, he was “very worried about what will happen in the future”.

“Eventually we may have a problem, and with reproduction in general, and it may be the extinction of the human species,” he told the BBC.

Pesticides, hormone-disrupting chemicals, diet, stress, smoking and obesity, have been named as plausible causes for the rate of decline, which researchers have said shows no sign of “levelling off”.

The same trend was not seen in other parts of the world such as South America, Africa and Asia, although the scientists said fewer studies had been carried out there.

One expert commenting on the study said it was the “most comprehensive to date”, and described the figures as “shocking” and a “wake-up call” for urgent research into the reasons driving the fall.

Writing in the journal Human Reproduction Update, the researchers – from Israel, the US, Denmark, Brazil and Spain – said total sperm count had fallen by 59.3 per cent between 1971 and 2011 in Europe, North America, Australia and New Zealand. Sperm concentration fell by 52.4 per cent.

"Sperm count and other semen parameters have been plausibly associated with multiple environmental influences, including endocrine disrupting chemicals, pesticides, heat and lifestyle factors, including diet, stress, smoking and body-mass index,” the paper said.

“Therefore, sperm count may sensitively reflect the impacts of the modern environment on male health throughout the life course.”

Chemicals linked to lowering sperm count include some used to make plastics more flexible and flame retardants used in furniture. These can enter the food chain after they are taken in by plants or eaten by animals.

A diet high in alcohol, caffeine, processed meat, soy and potatoes may also have an adverse effect on male fertility.

Aside from the obvious implications for reproduction, the researchers said the declines were consistent with reported trends in testicular cancer, the number of children born with one or both testicles missing, the onset of male puberty and total testosterone levels.