What do falling sperm counts mean for human survival? Robin McKie and Euan Ferguson report from London
IF there’s a subject guaranteed to raise a puerile snicker, then sperm – and its fate – have been sure-fire winners down the years. Yet sperm is the stuff upon which our survival depends.
Recent confirmation that supplies now appear to be running out – at an alarming rate – suggests the laughing may soon have to stop. The situation is now so serious that the United Nations has asked the Smithsonian Institution in Washington to host a two-day conference later this month.
More than 70 of the world’s experts will consider whether a body should be set up to co-ordinate research and conduct a global assessment.
The latest study, carried out by Finnish scientists and published in the British Medical Journal, showed a stunning drop in the numbers of men capable of normal sperm production – from 56,4% to 26,9 % – between 1981 and 1991. In addition, men’s testes were found to be shrinking.
At this rate, there will soon be no men capable of propagating our species. Humanity will end its days in a grim, infertile world populated by dwindling bands of survivors – just as PD James predicted in her 1992 best-seller, The Children of Men.
“We are not quite at the stage of The Children of Men, but we now have got to sit up and listen,” said Dr Simon Fishel, of Nurture, a reproduction research organisation.
It is not just the rapidity with which sperm production has dropped that has startled scientists. The fact that this sharp reduction has been discovered in Finland, the one Western nation lauded for having quality sperm, and lots of it, has also caused disquiet.
“The world is not yet at the stage to be alarmed,” said Dr Stuart Irvine, of the British Medical Research Council’s reproductive biology unit in Edinburgh. “But we should now be very concerned.”
In other words, the apocalypse is not yet with us. But the danger signals are clear – and have taken a remarkably short time to appear.
The first authoritative mention of falling sperm counts was made in 1992, at a time when commentators were already lamenting the dilemmas of modern manhood.
Feminism and long-term unemployment had generated a crisis of male identity. Men seemed only good for one thing – procreation – until Danish professor Niels Skakkebaek published a paper in the British Medical Journal suggesting they could no longer manage even that.
He and colleagues studied 60 scientific papers published over the preceding half- century, covering nearly 15 000 men, and concluded there had been a “highly significant” decrease in sperm count and a twofold rise in testicular cancer.
Over the next four years, these results were reproduced – with varying degrees of success – by French, British and American scientists.
Some found alarming declines in sperm counts, a few found none, while some uncovered strange variations: one suggested that men in New York had almost three times more sperm than those in Seattle.
Such differences are not surprising. Sperm counts can vary for many reasons, not all related to the condition of the testes. Counting objects so small that 50-million can swim comfortably in a millilitre of liquid is decidedly tricky, for one thing.
“You have to take a tiny, tiny sample, count the sperm in it and then multiply up from there to get a person’s total count,” says Professor Lewis Smith of Britain’s Institute of Environmental Health. “If you make the slightest mistake, that error is amplified thousands of times.”
In addition, sperm count is affected by sexual behaviour. As Smith puts it: “Those fortunate enough to ejaculate regularly have lower sperm counts than those who do not.”
In effect, the testes act like car factories. “If you close the factory gates, while cars continue to pour off assembly lines, you get an increasing build-up of vehicles,” said Irvine. “The longer you keep them shut, the more will pour out when you open the gates. It’s the same with sperm.”
Without knowing a subject’s ejaculatory history, researchers are unable to compare data reliably. The Finnish study avoided this problem because the Helsinki University researchers – led by Dr Jarkko Pajarinen – dissected the testes of cadavers.
The Finnish research is not alone in raising the alarm. The Worldwide Fund for Nature, which has also been studying human sperm decrease – having watched other animals come perilously close to extinction because of infertility – says cases of cryptorchidism (undescended testicles) in England and Wales doubled between 1962 and 1981.
Similar increases have been seen in Sweden and Hungary. Men with undescended testicles are more prone to testicular cancer, and usually have fewer and more abnormal sperm.
Enlargement of the prostate gland now afflicts 80% of men by the age of 70 in Western countries, and prostate cancer – which is also associated with sperm abnormalities – is now the most common cancer in the United States.
But why are we seeing this dramatic change, and in particular why are sperm counts dropping?
Initially, everything from tight underpants to increased daily stress was blamed. However, evidence soon pointed the finger at increasing levels of the female hormone, oestrogen – or its artificial derivative, a class of compounds called xenoes-trogens.
Studies on rats showed that long-term exposure to oestrogen can induce prostate cancer. It was argued that these substances were accumulating in the environment, for instance in the water supply, an idea seized upon by Greenpeace. It launched a campaign claiming that pollution was making penises smaller.
In 1995, a report by Smith’s team carefully showed there was enough uncertainty over the role of xenoes-trogens in sperm counts to make further research advisable.
“I don’t think xenoestrogens in the water are to blame, they are too diluted,” said Smith. “But perhaps such contaminants in the food supply, or possibly just changes in diet are the cause.”
Gwynne Lyons, a pollution expert with the Worldwide Fund for Nature, endorses suspicions about environmental pollution: “We know exposure to some plastics, and other man-made products associated with plastics, can cause a clear drop in the testicular weight and sperm production of rats, and now something similar is happening to humans.”
She believes the main chemical culprits are phthalates, used to soften plastics and as bases for inks often used on food packaging, though other chemicals, particularly pesticides, may also have a role.
Lyons is also convinced the situation will get worse, arguing that the sperm problem is tied more closely to a male’s birth than to his later years. This occurs because the mother is exposed to xenoestrogens, phthalates or whatever, and these affect foetal cells.
Nevertheless, low sperm counts do not necessarily produce infertility – the real global fear. “When we tested male contraceptives, we found men with vanishingly tiny levels but who could still impregnate women,” said Irvine. “Nevertheless, there is evidence to link the two phenomena. Recent studies have shown that couples in countries noted for having low sperm levels take longer to conceive babies than those with high levels.”
Humanity, which once feared overpopulation as its nemesis, may soon be devastated by its opposite, an irony not lost on Baroness James, who describes The Children of Men as “more of a Christian fable than science fiction”.
She is also conscious that, with a one-off excursion into the genre of HG Wells, Aldous Huxley and George Orwell, she may have got the dystopian future more unhappily right than the experts. It gives her no satisfaction: “It was a one-idea book, written after I read a review of a report into this issue. I hadn’t expected this to happen.”
Today the prognoses were for others to make, she said, but there was, objectively, little reason to believe we are fundamentally destined to survive.
“I remember one aspect that struck me about the review was the explanation that many types of human forms had already existed on this planet, and died out. Are we sure we’re so scientifically advanced today that the process won’t continue?”