Could humanity be extinct within 10,000 years? A new book is the wake up call our species needs

In H.G. Wells’ dystopian 1895 novel The Time Machine an unnamed Victorian scientist travels to the year 802,701. Instead of finding a flourishing, enlightened human civilisation reaping the cumulative benefits of millennia of economic and intellectual growth, he finds a horror scene. Here, gentle humans called Eloi are now the farmed food for the troglodyte-like Morlocks.

Science writer Henry Gee paints a less horrific but equally worrying picture of humanity’s future in his book The Decline and Fall of the Human Empire. Unlike Wells, Gee doesn’t see the human species capable of surviving longer than the next 8000-12,000 years.

This number is not an educated guess, or pessimistic opinion. It is based on statistical analyses that show our species is quickly degenerating amidst the chaos of our rapidly declining environments.

Review: The Decline and Fall of the Human Empire: Why Our Species Is on the Edge of Extinction – Henry Gee (Picador)

While all this might sound depressing, this book is a strangely engrossing read, addictive because of its continuum of interesting facts about our species’ origins and inevitable decline, and how we have impacted our planet in many unexpected ways. At times sarcastic, Gee’s book is more than just a monologue on our future. It could well be the ultimate wake up call to action for all of us.

A senior editor at Nature magazine, with a PhD in bovine palaeontology, Gee is also an accomplished writer of both popular science books and sci-fi novels. He writes in simple prose garnished with wit and humour, distilling complex science into an accessible read, a rare craft which won him the 2022 Royal Society Trivedi Science Book Prize for his previous book, A (Very) Short History of Life on Earth.

His new book takes a stoic look at humanity’s ultimate decline. This is something, he argues, we as a species cannot avoid, due to our damaging impact on the planet’s many environments, some of which are vital for our future food security. He does offer some hope for our survival beyond this time-frame, but it would rely on drastic, unlikely solutions.

The book is organised into three parts: Rise, Fall and Escape. Each details the story of our unique species from its prehistoric beginnings though to our success as the dominant mammal on Earth, and finally, to our fate in being too successful.

The rise of our species

“Rise” summarises a deluge of recent information about our ancient origins. Our modern human species, Homo sapiens, diverged from earlier human species around 300,000 years ago. We lived alongside a number of other such species at this time.

Genetics tells us a lot about our current population stability. Early human species almost went extinct before leaving Africa due to severe climatic events some 930,000–813,000 years ago, when the breeding population shrunk to an estimated 1,280 individuals on the entire planet. Modern Homo sapiens evolved later as a result of interbreeding amongst and between other archaic human species such as Neanderthals and Denisovans, the latter known from ancient DNA preserved in isolated small bones.

Only a small number of modern humans who evolved in Africa ever moved away from this continent, starting around 60,000 years ago. These eventually became our living human population of the world today. As Gee points out, “migration, is of course, the natural state of humanity”, a lesson with great implications for how we treat migrants today, many of whom are forced to flee war-torn or environmentally degraded areas.

I found this section full of fascinating new perspectives. For example, I didn’t know human populations in the past were very small. Fossil human remains are incredibly rare in most sites, full of many other kinds of mammals or bird remains.

Secondly, the populations of early Homo sapiens show great variability, indicating past populations were mostly isolated, not mixing very much. Small populations are more susceptible to natural disasters, so are easily wiped out by floods, tsunamis, fires, volcanic eruptions or other local events, keeping population numbers small.

Despite all this, we rose to over one billion people on the planet by the 1800s and to 8 billion today, fuelled by massive increases in agriculture and technology. The former provided enough food to sustain larger populations, the latter lengthened lifespans.

However, some researchers predict our population will peak at around 9.73 billion by about 2064, declining to 8.79 billion by 2100.

Other scenarios from the same source, involving better education and contraceptive access, predict the 2100 population at around 6.29 billion, and a decline from then onwards, eventually leading to a collapse once other factors, such as our declining fertility rates (leading to older populations, and labour shortages), kick in.

The fall of our species

The story of the royal Hapsburg family demonstrates how inbred human populations can lead to a host of debilitating disorders in future generations.

Between 1450-1750 there were 73 Hapsburg marriages, many between near relations. Uncles married nieces. First cousins twice removed married. This culminated in Charles II, the last Hapsburg king of Spain, who suffered many bouts of disease including rickets all his short life (he died at age 38) and couldn’t conceive any offspring. This is clearly not good for the species.

Random pandemics or diseases can, of course, strike populations without warning. Several evolved due to the growth of agriculture, when humans and animals came into closer contact. Viruses like flu, TB and plague are some examples of animal-borne diseases that jumped to humans, exactly as COVID did in 2020, though in that case not from a domesticated source.

The decline in our ability to reproduce as efficiently as in past populations is another worry for our species. The loss of the Y Chromosome in men, which is degenerating rapidly, is a disturbing trend, (though it may be addressed through genetic technology in the future). However, in some countries, male sperm counts and sperm quality are declining at an alarming rate.

The first detailed account of this, by Danish gynaecologist and obstetrician Elisabeth Carlesen and her team, showed sperm counts halved between 1940 and 1990. In Nigeria, sperm count and quality has dropped by 72.6% over the past 50 years.

Why is this happening? We don’t know yet. Gee cites as possible causes the increased human exposure to fossil fuel derivatives (in micro-plastics, and through other pollutions), climate change, or simply, our lifestyles.

To keep our population stable, every woman on the planet needs to have 2.1 babies (this number is the TFR or Total Fertility Rate). Even today many countries are dipping below this. China had a fertility rate of 1.18 in 2022. Japan’s was 1.26 in 2022 although the total fertility rate of all African nations in this year was 4.155. Globally, however, fertility rates are decreasing rapidly.

Survival or extinction?

The timing for our species extinction or “Doomsday scenario” is calculated using a statistical method developed by Princeton astrophysicist J. Richard Gott. The method is based on a statistical argument that we are living in the 95% range of humanity now, so we are more than 2.5% away from either the beginning or end of the species. (NB, this reasoning is complex, fully explained in the book.)

The average age of other human species (now all extinct) is mostly less than 2-3 million years. Our species has only been around about 300,000 years. However, if we are nearer the end of our species than the beginning, (assuming multiple factors leading to environmental collapse would happen sooner rather than later), Gee states,

I’d venture – with suitable hand-waving – that Homo sapiens will disappear from the Earth within the next 10,000 years.

Another argument about our imminent demise comes from “extinction debt”: when species destroy their habitat and eventually run out of resources. We humans have become the dominant species, pushing many thousands of species to extinction by altering habitats for growing food, harvesting wood, dumping our waste and so on.

Humans use about 25% of the world’s plants’ generation of photosynthesis as our food, a figure that has doubled since 1910. Humans and our domesticated animals make up 96% of all the mass of mammals on the planet. Around 70% of all birds on Earth comprise our poultry populations. And on it goes. The balance of nature is now changed forever, so predicting stability in long-term food security is way more difficult.

We humans represent a new force of evolution changing the biomass and reshaping most of our terrestrial ecosystems. We are also changing many marine ones, due to increased pollution, large-scale, over-fishing and the impacts of commercial shipping routes.

What to do?

All of this begs the question what can we do now? The answer is not about saving our species forever (all species have a finite lifespan). It’s matter of how much time do we have?. We can extend our species chances of longer survival if we can save our planet from further destruction and imminent environmental collapse, but we must we act now to do so.

The solution is simple. Science gives us clear directions as to how to mitigate climate change (by seriously reducing our production of greenhouse gases causing it); and how to restore damaged habitats (by cleaning them up). Politics unfortunately usually gets in the way of saving the planet due to human greed taking priority over any serious attempts at real progress in this area.

Gee has an elegant, if highly unlikely solution to saving our species. It might just be possible in the next century or so, he writes, with the increased pace of technology, to sustainably develop human colonies on the moon or Mars. We need first to develop a self-sustaining ecosystems that will provide food, clean air and all the resources necessary for life in order to survive on long distance space travels.

Despite various attempts, it has not been possible so far to survive in our own self-contained, mini-ecosytems, as seen by the failure of Biosphere 2 in the Arizona desert in the 1990s.

This gigantic terrarium (1.27 hectares) had 3000 species of animals and plants, with eight humans living inside its enclosed walls. It seemed to work well for a while, but over time bacteria in the soil took too much oxygen while the thick concrete walls sucked all the carbon dioxide out of the air, starving plant life. Crops failed and their pollinators, the birds and bees, also died. The experiment lasted under three years before the humans inside had to break the seal to let fresh air in.

Gee predicts the settlement of space will one day happen, but he suggests we are at least two to three centuries away from that goal.

While the topic of this book might seem a little depressing, it is really a powerful wake up call to all of us, based on the very latest scientific research.

The stoics say if we can’t do anything about a problem, we shouldn’t worry about it. But in this case there is a lot we can all do. Voting for the right people who will enact change is the first step. This book should be mandatory reading for all politicians.

John Long receives funding from The Australian Research Council.