Early this morning, January 1, 2021, three minutes after midnight, the last human being to be born on earth was killed …
Thus begins Children of Men, a dystopian novel by P.D. James (1992). A sudden and unexplained loss of human fertility tipped the world toward apocalypse. Whereas the book held testes to be responsible, the movie version directed by Alfonso Cuaron switched the cause to gynecology, sparing those precious nuts from blame!
It’s possible for a scientist to suspend disbelief in science fiction, but he/ she always prefers to have facts. I had a professional interest in fertility, both female and male. When I first read about a dip in sperm counts, I dismissed it as a statistical quirk or fiction, but no longer. A study combining 185 studies amounting to 42,000 men found average sperm counts have dropped almost 60% in 40 years to 2011 in Western cultures. The trend continues. The paper didn’t report sperm quality (depicted above), a pity because ours is much poorer than in any other species.
The cause is unknown although experts offer similar suggestions to James—lifestyle and/ or pollution. The average count has fallen below 50 million per milliliter, the range of subfertility. While worrying for people who plan to start a family, I wonder what else it portends. Not a plunging population, but possibly raising other alarms if sperm are honest biomarkers.
During development, sperm are shorn of the apparatus that protects and repairs other cells. Short-lived, they only live a couple of days under the best conditions. They could be harmed by toxins in testicular fluids or further along from glandular secretions that contribute to semen. Bad enough if only these specialized cells are harmed, but what if the damage is already done to their stem cell parents? If they are vulnerable to a hidden threat perhaps other cells are affected, and in women as well as men. Could discovery of the affliction of sperm lead to a better understanding of today’s prevalence of some chronic diseases and impacted immune systems?
One in four men who develop mumps have orchitis as fluid builds up to create pressure inside the rigid capsule of testes. Hence, they lose fertility. That the MMR vaccine has greatly reduced the risk of the disease makes the population-wide decline in sperm counts more striking.
But what role for other airborne RNA viruses, especially from the onslaught in recent SARS epidemics and now a pandemic? Cells in testes and ovaries express the ACE-2 receptor, the spike protein that binds the SARS-COVID-19 virus so it can step into cells. A recent study at Columbia University, New York, reported only one covid patient with a low sperm count and virions in his semen, so the risk of infertility or sexual transmission of covid seems slight. Science is still pending a final decision but already concluded the vaccine does no harm to fertility, quashing anxieties in the media.
The human population won’t crash even if every living person became infertile overnight. Vast numbers of semen samples are stored in freezers around the world and frozen cells are good for decades if not centuries. Besides, a few sperm can be found in almost every clinically sterile testis, all that is needed for fatherhood by injecting eggs using the ICSI technique launched the same year as James published her book.