The Decline and Fall of the Human Empire: Science Writer Henry Gee Argues Humanity Is on a Rapid Path to Extinction

Since the beginning of time, animals have risen and fallen from dominance on planet Earth. Had the dinosaurs not been wiped out by a freak asteroid, their time as the supreme animal on Earth would have faded, too. In The Decline and Fall of the Human Empire, award-winning science writer Henry Gee offers a concise, brilliantly told history of our species—and argues that we are on a rapid, one-way trip to extinction, though we can take steps to delay this fate for a short while. The fascinating read is now available in paperback.

Prologue

In a composition of some days, in a perusal of some hours, six hundred years have rolled away, and the duration of a life or reign is contracted to a fleeting moment: the grave is ever beside the throne; the success of a criminal is almost instantly followed by the loss of his prize; and our immortal reason survives and disdains the sixty phantoms of kings who have passed before our eyes, and faintly dwell on our remembrance.

— Edward Gibbon, The Decline and Fall of the Roman Empire

Of all the animals that have risen and fallen in Earth’s long history, it is the dinosaurs that have most engaged the public imagination. They infest our cinemas and comics. Their images are all over clothing and school lunchboxes. They even get into places that they’re not wanted. The word “dinosaur” has such cachet—such pulling power—that it can even sell things that don’t have much to do with dinosaurs.

Dawn of the Dinosaurs is the title of a wonderful book about the unjustly neglected Triassic Period (the one before the Jurassic of movie fame, for all that many of the dinosaurs featured therein are from the even later Cretaceous Period), a fifty-million-year interval between 250 and 200 million years ago in which many kinds of extraordinary creatures evolved. Most of these creatures, despite their inherent interest, will be unfamiliar to most people, and dinosaurs only played a walk-on part near the end. But they got top billing on the title page, nonetheless.

Such palaeocultural misappropriation doesn’t stop there. Popular books on prehistoric life are often entitled “Dinosaurs”, and then, in smaller letters, as if in apology, “and Other Prehistoric Animals”. Play sets featuring dinosaur models might include animals that lived at the same time as dinosaurs but weren’t dinosaurs, such as the flying pterosaurs and swimming plesiosaurs. They might even include Dimetrodon, a toothy, sail-backed creature that lived tens of millions of years before the dinosaurs and was, in fact, more closely related to us. As if to stick two fingers up at the merest accusation of anachronism, they might even throw in a woolly mammoth, an animal that lived more than fifty million years after the dinosaurs had disappeared.

Such is the near synonymy of the word “dinosaur” with “clickbait” that Henry Gee was tempted to call his book Dinosaurs in large capital letters with the subtitle in smaller letters, and Their Role in the Evolution and Extinction of Humans.

The Enduring Mystery of Extinction

They are not, however, completely unconnected. Whatever else one might say about dinosaurs, they are, indubitably and most definitely, extinct. The fascination that they elicit in the public mind is derived, in large measure, by this single, simple fact. Dinosaurs seemed to be thriving until the very end of the Cretaceous Period about sixty-six million years ago, when, suddenly, they disappeared, along with the flying pterosaurs, the swimming plesiosaurs, the iconic truck-tyre-sized ammonites—armoured relatives of squid that are definitely not dinosaurs—and many other creatures.

For many years—decades, even—the reason why dinosaurs perished was a non-question that attracted a wealth of possible answers. More than a hundred have cluttered up the cocktail-party-chat end of the scientific literature. Dinosaurs died out because their eggshells became too thin and fragile for the embryos to reach term. Alternatively, some argued their eggshells became too thick for the young to hatch. Other theories suggested dinosaurs died out because newly evolved mammals ate their eggs, irrespective of the shell thickness, or because of indigestion brought on by eating newly evolved flowering plants. Some even claimed dinosaurs died from hay fever contracted from those same plants and sneezed to death, or succumbed to some other unspecified contagion.

Other proposals suggested dinosaurs died out because they became too big and heavy, or because they stopped having sex. Another notion was that, after 160 million years as the undisputed rulers of creation, they simply ran out of things to do, had no new worlds to conquer, got bored—a condition that has accreted its own technical term, Palaeoweltschmerz—and expired from sheer ennui.

The most outrageous idea to account for the extinction of the dinosaurs was that the world was struck by an enormous asteroid, the impact of which ushered in an interval of global catastrophe. This was the idea that turned out to be true.

Many of the earlier ideas turned on the notion that after a hundred million years and more of tenure on the Earth, the dinosaurs had become outmoded, tired, worn out, and that their time was over. This, really, was why extinction was once treated as a kind of non-question. It was once thought that dynasties of creatures came and went as a matter of course, and that departure was inevitable once creatures had run out of puff.

It was called “racial senescence”, or, more technically, “orthogenesis”. And so it was that the Devonian Period was dubbed the “Age of Fishes”, after which fishes gave way to the succeeding “Age of Amphibians” in the Carboniferous Period. Each dynasty of creature gave way to something newer, more advanced, and more evolved, with each in its allotted station and allotted span. The dinosaurs were viewed as the apotheosis and zenith of the “Age of Reptiles”, after which there was the “Age of Mammals”, culminating in Man—with a capital M, and notably not Woman. Dynasties of animals arrived, largely supplanted existing ones, and were in turn eclipsed. Dinosaurs arrived, fretted and strutted on the stage of life, and then departed when their time was up. The word “dinosaur” even became a synonym for something huge, obsolescent, and unsuited to the modern world, like the Ford Edsel or manual typewriters.

Reimagining Evolution and the Red Queen Hypothesis

Only in the 1970s were dinosaurs reinvented as warm-blooded, intelligent creatures, largely thanks to the patient work of the late palaeontologist John H. Ostrom and his swashbuckling student Robert Bakker. A little later, the idea that an asteroid brought the age of dinosaurs to a crashing close gained credence, proving that dinosaurs didn’t die out because of some natural cycle, but were cut down in their prime. If the asteroid had missed, dinosaurs might still be enthroned on the Earth today.

After this, orthogenesis was dumped in the “where are they now?” files of defunct evolutionary ideas. It was an idea that had had its day, much like the dinosaurs themselves. Evolution does not work that way. The motor of evolution is natural selection, a handy phrase for what happens when inherited variation and superabundant offspring confront environmental change. When this collision is allowed to play out over time, the result is evolutionary change. But at any given moment, natural selection has no memory of things past, no vision for the future, and no aim in view.

This in-the-moment view was encapsulated by palaeontologist Leigh Van Valen as the “Red Queen” hypothesis. Creatures are forever in competition. Predators develop keener weapons and sharper senses to catch prey that are forever evolving to be more alert and wary. As the Red Queen says to Alice in Lewis Carroll’s Through the Looking Glass, in Looking-Glass Land you must run as fast as possible just to stay in the same place. From this, Van Valen reasoned that there need be no relationship between how long a species took a turn on the stage of life and the timing or manner of its passing. Orthogenesis and racial senescence were an illusion.

Except that, in a way, they weren’t.

Time after time, palaeontologists found that species, or more usually genera—groups of closely related species—tended to arrive at one point in Earth’s history, after which they diversified and became dominant, only to fade and dribble away to extinction. If orthogenesis made no sense, what could explain this pattern of entrances and exits?

An answer came as recently as 2017, when a group of palaeontologists from Helsinki came up with a way to finesse the problem. Species appear on the scene for any number of reasons, but their rise to dominance is driven by having to rub up against other creatures, in the same way that it takes a bit of irritating grit in an oyster to create a pearl. Once they reach the top, having run all the competition out of town, they must fight a long and inevitably losing battle against a pitiless foe that will never give up—the Earth itself. After that, the only way is down, until eventually the tiny remnant of what is left will be culled by some chance environmental event.

The asteroid that mowed down the dinosaurs was a freak event. If the asteroid had missed, the dinosaurs would have died out sooner or later, because that is simply what living things do. To understand when and why species become extinct in the common run of things, one must examine what they were doing at their peak.

The Inevitable Fate of Homo sapiens

This brings the discussion directly to the connection between dinosaurs and humans. If this logic is applied to modern humans, our own species, Homo sapiens, is marked for extinction. Of course it is. Humans, like dinosaurs and every other living thing that has ever walked, hopped, crawled, burrowed, flown, or slithered into the ocean depths, are living creatures and cannot claim any special exemption from the rules of the world.

On the other hand, Homo sapiens might not be an exception, but it is exceptional nonetheless, a fair statement even when judged by a human. Humans have achieved, in a remarkably short space of time, a dominance over the fates of all other creatures that no other species has managed in the entire history of the Earth, as far as is known. They have managed this with an unprecedented mastery over the forces of nature. Humans have penetrated the secrets of atoms to exploit their energy, unravelled the genetic mysteries of life to manipulate it, and scanned the very edges of the Universe. It is reasonable to ask whether, given all these achievements, humans might uniquely evade extinction’s great scythe and persist indefinitely.

The answer, Gee argues, is that humanity will perish along with everything else. The reason is due, in part, to its very success. Humanity has become so pre-eminent and dominant that it threatens the functioning of the ecosystem on which it and all other creatures depend. No other single species in the history of creation has ever posed such a threat.

In his previous book, A (Very) Short History of Life on Earth, Gee was coy about precisely when Homo sapiens might vanish, veering between a few thousand years, a few tens of thousands of years, or a vague future timeframe described simply as “sooner or later”. Extinction is not a uniform event; rather, it affects each species according to its own circumstances. In that work, Gee coined the Karenina Principle—the idea that whereas all happy, thriving, abundant species are the same, each species on the brink of extinction will meet oblivion in its own way.

There are, however, rules. According to the principles discovered by the Helsinki group, the inevitable demise of our species was set the moment when, for the first time in the seven-million-year history of the human lineage, only one human species was left standing: Homo sapiens. That critical turning point occurred at some point between 50,000 and 25,000 years ago. After that, the downward course became inexorable, leaving only the question of when the final curtain would fall.

The Last Human Standing

Until about 50,000 years ago, Homo sapiens was just one of many species of human. At that time, it was primarily tropical, living in Africa and southern Asia, with a toehold in island southeast Asia and Australia. In Europe and central and northern Asia, Neanderthals ruled, ruggedly adapted for ice age life. They shared central and eastern Asia with the Denisovans, initially adapted for high altitudes on the Tibetan Plateau before migrating to lower altitudes.

Island southeast Asia hosted a remnant of the ancient species Homo erectus in Java, along with the unusual, dwarfed “hobbits” such as Homo luzonensis in the Philippines and Homo floresiensis on the island of Flores in modern-day Indonesia. These are merely the species currently known to science, while Homo sapiens also shared Africa with other groups whose existence is barely understood.

By around 25,000 years ago, coincident with the coldest snap of the ice age, Homo sapiens had colonized the whole of Africa and Eurasia and made inroads into the Americas. In the process, it had driven all other human species to extinction. From the moment the last human that wasn’t a member of the all-conquering Homo sapiens died out, the species’ fate was sealed. It began its long, losing battle against ineluctable fate.

While the human career since then appears to be a story of progressive global domination, beneath the surface Homo sapiens has been living on borrowed time for thousands of years and is now on the verge of collapse, according to the book’s thesis.

The Decline and Fall of the Human Empire explains why this is happening, while also outlining how humanity—if it proves wise, lucky, and sufficiently ingenious—might evade this fate, at least for a while. To achieve this, however, Gee stresses that humanity must act immediately, as people alive today find themselves at a unique turning point in the long history of the species.