The Sixth Extinction: An Unnatural History

by Elizabeth Kolbert

If there is danger in the human trajectory, it is not so much in the survival of our own species as in the fulfillment of the ultimate irony of organic evolution: that in the instant of achieving self-understanding through the mind of man, life has doomed its most beautiful creations. —E. O. Wilson

The word “Anthropocene” is the invention of Paul Crutzen, a Dutch chemist who shared a Nobel Prize for discovering the effects of ozone-depleting compounds. The importance of this discovery is difficult to overstate; had it not been made—and had the chemicals continued to be widely used—the ozone “hole” that opens up every spring over Antarctica would have expanded until eventually it encircled the entire earth. (One of Crutzen’s fellow Nobelists reportedly came home from his lab one night and told his wife, “The work is going well, but it looks like it might be the end of the world.”)

Owing to a combination of fossil fuel combustion and deforestation, the concentration of carbon dioxide in the air has risen by forty percent over the last two centuries, while the concentration of methane, an even more potent greenhouse gas, has more than doubled.

The way corals change the world—with huge construction projects spanning multiple generations—might be likened to the way that humans do, with this crucial difference. Instead of displacing other creatures, corals support them. Thousands—perhaps millions—of species have evolved to rely on coral reefs, either directly for protection or food, or indirectly, to prey on those species that come seeking protection or food.

It is estimated that at least half a million and possibly as many as nine million species spend at least part of their lives on coral reefs.

One of the defining features of the Anthropocene is that the world is changing in ways that compel species to move, and another is that it’s changing in ways that create barriers—roads, clear-cuts, cities—that prevent them from doing so.

Though it might be nice to imagine there once was a time when man lived in harmony with nature, it’s not clear that he ever really did.

Then, roughly thirty thousand years ago, the Neanderthals vanished. All sorts of theories have been offered up to explain the vanishing. Often climate change is invoked, sometimes in the form of general instability leading up to what’s referred to in earth science circles as the Last Glacial Maximum, and sometimes in the form of a “volcanic winter” that’s believed to have been caused by an immense eruption not far from Ischia, in the area known as the Phlegraean Fields. Disease is also sometimes blamed, and so, too, is simple bad luck. In recent decades, though, it’s become increasingly clear that the Neanderthal went the way of the Megatherium, the American mastodon, and the many other unfortunate megafauna. In other words, as one researcher put it to me, “their bad luck was us.”

given a shave and a new suit, the pair wrote, a Neanderthal probably would attract no more attention on a New York City subway “than some of its other denizens.”

Archaic humans like Homo erectus “spread like many other mammals in the Old World,” Pääbo told me. “They never came to Madagascar, never to Australia. Neither did Neanderthals. It’s only fully modern humans who start this thing of venturing out on the ocean where you don’t see land. Part of that is technology, of course; you have to have ships to do it. But there is also, I like to think or say, some madness there. You know? How many people must have sailed out and vanished on the Pacific before you found Easter Island? I mean, it’s ridiculous. And why do you do that? Is it for the glory? For immortality? For curiosity? And now we go to Mars. We never stop.”

it should be possible to identify the basis for our “madness” by comparing Neanderthal and human DNA. “If we one day will know that some freak mutation made the human insanity and exploration thing possible, it will be amazing to think that it was this little inversion on this chromosome that made all this happen and changed the whole ecosystem of the planet and made us dominate everything,” he said at one point. At another, he said, “We are crazy in some way. What drives it? That I would really like to understand. That would be really, really cool to know.”

Having cut down our sister species—the Neanderthals and the Denisovans—many generations ago, we’re now working on our first and second cousins. By the time we’re done, it’s quite possible that there will be among the great apes not a single representative left, except, that is, for us.