In 1739, a company of French soldiers together with a few hundred of their Native American allies were heading down the Ohio Valley en route from New France to Louisiana when they came across a sort of natural time capsule.
When the troops stopped to camp downriver from present day Cincinnati, some of the natives headed off into the woods to hunt. A few miles away, they found a strange marsh full of animal bones. The marsh had apparently ensnared all manner of beasts unfortunate enough to have wandered into its pungent and muddy waters – among them a creature with 10-pound teeth, an enormous tusk and an elephantine thigh bone.
The commander of the company was Charles le Moyne, the second Baron de Longueuil, and governor of Montreal. When presented with the teeth, tusk and bone, he was sufficiently impressed to take them along for the rest of the expedition. Reaching New Orleans after many mishaps, Longueuil shipped the strange finds off to France and their ultimate destination, the personal collection of King Louis XV.
Jump to 1795 – not long after the French Revolution abruptly and violently eliminated the French monarchy. By then, the king’s collection had become the Muséum national d’histoire naturelle and Longueuil’s curious specimens had come to the attention of a 25-year-old zoologist named Georges Cuvier.
While puzzling over what he saw, Cuvier made an intellectual leap that upended a piece of conventional wisdom as old as Aristotle: the assumption that the animals we know today are the only animals Earth has ever known. Cuvier showed it could not be so. While the remains plucked from the Kentucky marsh were elephant-like, they were not exactly of an elephant. So what were they? Cuvier argued that they belonged to an espèce perdue, a lost species.
In his study, Cuvier had come nearer than any of his predecessors to perceiving the biological guillotine of extinction. And the mysterious, big-toothed creature – which he dubbed “mastodon” – would turn out to be just one of its many victims.
Since Cuvier’s seminal insight, scientists have come to understand that countless species have fallen by the evolutionary wayside as part of the normal course of things. Most of the time, the rate of extinction is slow and steady. For mammals, it works out to about one species among thousands passing into oblivion every 700 years.
But some disturbing exceptions have also come to light. The fossil record unequivocally shows that on five separate occasions during the past half-billion years, vast numbers of the world’s species – up to 95 per cent in the most extreme case – vanished in a geological instant, leaving behind a dramatically diminished biosphere. The precise causes of these mass extinctions are a matter of ongoing scientific debate, though the fifth and best known (the one that took out the dinosaurs and cleared the way for the rise of mammals) is known to have coincided with a direct hit from an asteroid.
Such cataclysmic events, with their ferocious power to rewrite the future of life across an entire planet, are all but unimaginable. Yet imagination is hardly required. If we look around, we can see we are in the midst of another such mass extinction right now. What’s more, writes journalist Elizabeth Kolbert in The Sixth Extinction: An Unnatural History, we are not only “witnessing one of the rarest events in life’s history, we are also causing it.”
The term Sixth Extinction has been in circulation since 1996 when anthropologist Richard Leakey and science writer Roger Lewin popularized it in a similarly titled book. Now, Kolbert, a staff writer at The New Yorker who is known for her series of brilliant pieces explaining the science and politics of climate change, picks up the theme and gives it a new and urgent focus.
Taking readers on a whirlwind tour across continents and eons, Kolbert’s destination is the front line of biological upheaval. In the process, she uncovers what scientists have learned about the process of extinction, and what it may portend for the future of life on Earth. The subject is well suited to Kolbert’s signature blend of vivid field reporting, fascinating excursions into history and clear explanations of technically complex research. The result is a troubling yet riveting examination of what happens when one species throws a spanner of epic proportions into the delicate machinery of global biodiversity. As Kolbert notes: this time, we’re the asteroid.