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Could Children of Men's Human Infertility Actually Happen?
It might already be happening.
We’re all familiar with the typical apocalypses. Movies and books have given us plenty of opportunities to wonder what might happen if we were struck by an asteroid or subjected to a nuclear wasteland. But the 2006 sci-fi dystopia Children of Men (now streaming now on Peacock) imagined an extinction of biological origin. It takes place in a fictional 2027, 18 years after the onset of global human infertility.
In the film, directed by Alfonso Cuarón and based on the novel by P. D. James, male fertility has dropped to almost zero and there hasn’t been a pregnancy in almost two decades. The youngest person on Earth is now an adult, and civilization already has one foot over the cliff.
A world without children is one without a future, a reality where the last living humans will slowly dwindle until no one is left. It’s a horrifying vision, but could it actually happen?
Can an entire species become infertile?
In recent years, scientists have documented a troubling drop in fertility across a wide range of animals, driven by a combination of environmental factors. Some changes in fertility are driven by exposure to certain chemicals in the environment. Other changes are driven by climate change.
Research suggests that males of some species are becoming infertile as a direct result of rising temperatures. We’ve known for a while that temperature impacts the ability of a species to survive, but recent research suggests that fertility declines at sub-fatal temperatures. Scientists are now learning that the survival of a species might be defined by the temperatures at which they can reproduce, rather than the temperatures they can survive.
Corals make fewer sperm and eggs when exposed to temperatures just 2 degrees Celsius warmer than usual. Similarly, many insect species see a sharp drop in reproduction when it gets too hot. The same is true for many fish, birds, and mammal species.
A study published in the journal Nature Climate Change looked at 43 species of fly to figure out if reproduction was impacted by temperature. They exposed the flies to four hours of heat stress and measured their fertility. Right away, 11 of 43 species experienced an 80% loss of fertility. It was even worse a week later, when 19 of 43 species showed decreased fertility. Of course, there are plenty of differences between flies and people, and it’s unclear if temperature impacts human fertility in the same way.
Human fertility may have dropped by as much as half since 1970
When it comes to humans, the impact of temperature is less clear, but there is still evidence that male fertility is on the decline. Typically, male fertility is assessed by determining sperm count. It’s a notoriously difficult process because sperm aren’t uniformly distributed in a sample and they move. Moreover, counting methods have evolved over time, such that comparing data sets is no easy task. All of which has led to some debate about how to interpret the data, or even if there is enough data to make a conclusion one way or another.
Some studies have shown a rise in fertility in some groups, others have shown no change over time, and others have demonstrated a significant drop in fertility. A 2017 study analyzed the results of 200 previous studies to quantify human male fertility from 1970 forward. That study concluded there was a 50% decrease in sperm count over the last 50 years. If that trend is confirmed and if it continues, humanity could have a significant fertility problem in just a few decades.
Assuming male fertility is on the decline, there are likely a number of factors. Endocrine-disrupting chemicals in the environment, lifestyle, and rising temperatures are all likely contributors. “Sperm count is largely affected by the environment, and by our lifestyle, because it’s manufactured all the time,” said study author Hagai Levine, via Scientific American. Levine said that even if the rate of infertility is incorrect, it’s still worth addressing. “We still better do something about it and not wait to see because some of the causes may be irreversible.”
Those endocrine-inhibiting chemicals impact a fetus during development, reducing fertility later on in adulthood. Sperm counts of today’s adults are at least in part defined by the chemical environment of those males when they were in the womb. Likewise, the fertility of the next generation will be defined by the chemical environment of today, which emphasizes Levine’s call to action. Any efforts we make to address declining fertility will need to be carried out at least one generation in advance.
Watch Children of Men, streaming now on Peacock.
