Henry Gee is a senior editor at Nature and the author of several books, including Jacob’s Ladder, In Search of Deep Time, The Science of Middle-earth, and The Accidental Species. He has appeared on BBC television and radio and NPR’s All Things Considered, and has written for The Guardian, The Times, and BBC Science Focus.
What’s the big idea?
Humanity is at a turning point: for the first time in ten thousand years, our population growth is slowing, and by mid-century, it will decline rapidly. In The Decline and Fall of the Human Empire, award-winning science writer Henry Gee argues that we are on a one-way path to extinction, facing dwindling resources, environmental collapse, and emerging threats that challenge our survival. While our species’ rise has been unstoppable—until now—Gee suggests that our only hope may lie beyond Earth, with a narrow window to establish colonies in space. Blending history, science, and wit, he presents a bold vision for humanity’s future, where survival depends on ingenuity, foresight, and cooperation.
Below, Gee shares five key insights from his new book, The Decline and Fall of the Human Empire: Why Our Species Is on the Edge of Extinction. Listen to the audio version—read by Gee himself—in the Next Big Idea App.
1. We are living at an inflection point.
They say that if you can remember the 1960s, you weren’t there. So many epochal events happened in that turbulent decade. The Vietnam War. The First human landing on the Moon. The Prague Spring. The Cuban Missile Crisis. Woodstock. The Beatles. The student protests of ’68. The assassinations of MLK and JFK. The commercial availability of the contraceptive pill. But you might not have heard of the most momentous event of the 1960s, the most critical event in human history for 10,000 years. It was in the 1960s that the rate of population increase peaked at just over 2 percent a year and started to fall, an unprecedented event since the origin of agriculture.
The population is still rising, but the rate of increase is slowing. Currently, it’s less than 1 percent and decreasing rapidly. By the 2060s, the population is expected to peak at 10-11 billion and then begin to decline sharply. By 2100, it could match the current level of 8 billion, and all projections indicate that the decrease will persist. By 2300, there might be as few as 1 billion people, which is comparable to the population during Napoleon’s era.
The causes are many and various:
- Female emancipation
- People are choosing to delay starting families.
- A decline in human sperm count.
- Overexploitation of resources.
- Overcrowding in cities, which is not the natural state for humanity.
The endpoint of these trends will be extinction, maybe as soon as 10,000 years. But why are these things happening now? One reason could be that in the past century or so, humans have exceeded the planet’s capacity to sustain them. The global economy has been essentially static for the past 25 years—no more economic growth is possible without improvements in sustainability more massive than any government could contemplate. All of this is made more difficult by the recent and rapid effects of human-caused climate change.
2. What can governments do?
The rapid decline in birth rates coincides with an increase in the average age of populations. The world is greying. Countries will need to either encourage people to have more children or import working-age individuals from other countries to maintain a tax base. The first solution (having more babies) isn’t effective. The second solution (importing individuals) is politically challenging.
However, if governments are wise, they should promote mass immigration now. The reason is that by 2100, even those countries currently exporting people will reach zero population growth, leading to competition among countries to attract immigrants. Nations that fail to take action will face significant decline. Unfortunately, governments tend to tackle problems by focusing on economic growth. The concept of growth, which is based on an ever-expanding market, is not sustainable. For an economy to remain stable, it must increase its population through immigration, which is often politically unappealing.
3. The lack of human genetic diversity.
We look like a varied bunch, we humans. We vary in skin tone from almost pure white to deepest black, with every shade in between. But these differences are really only skin deep. Under the skin, humans are remarkably the same genetically. There is more genetic variation in a single troupe of wild chimpanzees in West Africa than in the entire human population. The reason is that for almost all of human history, people have been extremely rare and spread very thinly across the landscape in small family groups. So rare that humans almost became extinct several times, dwindling to just a few thousand individuals, limiting the gene pool. Each new population expanded from this tiny, genetically depleted population. With each new expansion, genetic variation became less and less.
“There is more genetic variation in a single troupe of wild chimpanzees in West Africa than in the entire human population.”
This sameness means that we humans are inbred and thus extraordinarily prone to diseases and pandemics. Agriculture forced us to live close together with our animals, creating new diseases such as influenza and tuberculosis. Chimps have very few diseases, even though they have no personal hygiene, eat raw monkey meat and snack on their own poo. In fact, the worst diseases chimps get are contracted from humans.
When a population with limited genetic diversity completely occupies a single patch of habitat, it risks rapid extinction. In our case, that habitat is the entire planet, which we now dominate. Ninety-six percent of mammals by mass are humans and their domestic animals. Six out of every ten birds you meet are domestic poultry. Humans – just one species among millions – consume up to 40 percent of the total mass that plants produce through photosynthesis. By several measures, humans have exceeded the Earth’s capacity to support life. Because of these factors, humans are likely to face extinction very soon, in geological terms, perhaps within the next 10,000 years.
4. Could space be the answer?
If humans are to increase genetic diversity and avoid extinction, at least for a while (because, in the end, all species become extinct), the only answer will be to seed colonies outside the Earth, perhaps on the Moon, or Mars, or in artificial habitats, possibly inside hollowed-out asteroids. These colonies will have to have at least 1,000 colonists each to remain viable. Each colony will go its own evolutionary way, but they will have to interact occasionally with one another to keep the species together.
We have a long way to go. To date, only about 400 people have been to space, and only the Apollo astronauts have been above the magnetosphere that shields the Earth from harmful radiation from space. All have been men. Only 12 people have set foot on the Moon, all of whom are healthy white men, and none since 1972. Although human space flight seems to be on the verge of revival, many questions remain unanswered. No woman has traveled into deep space or had children. Nobody knows the long-term medical, social, or political consequences of living in space. The technology for maintaining self-sustaining habitats indefinitely is still in its infancy.
“It takes a civilization of billions to sustain the technological knowledge necessary for maintaining colonies in space.”
However, if we humans are to colonize space and avoid extinction here on Earth successfully, we must achieve that within the next 200 years. The reason is simple: if it takes a village to raise a child, it takes a civilization of billions to sustain the technological knowledge necessary for maintaining colonies in space. By 2300, the human population will have declined so significantly that no such innovation will be feasible. The question remains: why would anyone want to go into space, except perhaps for a fleeting glimpse of the view? Few are likely to desire permanent space habitation with the lofty goal of prolonging the species. Some individuals may be motivated by thoughts of exploration, but will this be sufficient if you’re in a cramped habitat millions of miles from Earth, and in need of a dentist? There are no rational reasons to venture into space, yet numerous irrational ones. Perhaps we should pin our hopes on these. Currently, these are very long odds.
5. The status of women.
Finally, I want to leave you with this: female emancipation may be one of the causes of the impending decline in the human population. But consider, in broad terms—humans now live longer, are healthier, better fed, and more educated than they were even fifty years ago, despite the massive increase in population since then. The single most important cause of this is female emancipation. Once women gain reproductive, social, and political governance over their own bodies, the workforce doubles, more children receive education, and people are healthier and better nourished.
For almost all human history, women have had one role—to produce babies. They began this as soon as they were old enough and continued until they died in childbirth or reached menopause. Reproductive self-governance—another achievement of the 1960s—is only about a century old, an eyeblink in historical terms. It could easily be taken away, and has been. Look at Afghanistan or the United States since the revocation of Roe v. Wade. The decline of the human race is inevitable, leading to much dislocation and conflict. Ultimately, these can only be mitigated by the remarkable innovation of female emancipation.
To listen to the audio version read by author Henry Gee, download the Next Big Idea App today:
