When Humans Ruled the Earth: The Inevitability of Mass Extinction

Image: Alan D. Pocaro

In the hierarchy of things that keep people awake at night, mass extinction may not rank very high. There are immediate calamities to contemplate: job loss, illness, broken relationships and all the other reefs upon which we so frequently shipwreck. Mass extinction—the wholesale disappearance of species across the biological spectrum—seems abstract by comparison.

Let’s underline that “seems,” though. Because mass extinction is already under way, and has been for some time. We may not have a strong sense of it—this is, after all, a very crowded planet (which is part of the problem)—but in fact, while biomass keeps increasing, biodiversity has cratered. To take just one example: sixty percent of all bird life on Earth now comprises a single genus: the domestic chicken. I could lay you flat with some other equally staggering percentages, but for the sake of fluidity, why not just take that one and extrapolate it. Extrapolate it really, really hard. Extrapolate it like you’re mad at it. Because you absolutely should be.

Nearly every day we’re buffeted by shrieking headlines about carbon emissions, deforestation, ocean deoxygenation, rising sea levels, the insect apocalypse… and yeah, it’s overwhelming. But it helps if you can see it all as part of a single narrative—the one where we burn up the planet and kill pretty much everything on it.

There have been five previous mass extinctions, all triggered by massive climatic or topographical shifts: the Ordovician-Silurian (440 million years ago), the Late Devonian (365 million years ago), the Permian-Triassic (250 million years ago), the Triassic-Jurassic (210 million years ago) and the Cretaceous-Tertiary (65 million years ago). The one we’re in is called the Holocene, after the current geological era, which began at the end of the Ice Age, circa 9700 BC. Which is, in geological time, the equivalent to about twelve seconds ago.

And this one’s almost entirely our fault; because what humankind has managed to do in that evolutionary eye-blink is jaw-dropping. This will be the first mass extinction event that can be classified as a suicide. (That’s why an alternative name for the Holocene extinction, the Anthropocene, has been proposed; it flat-out name-checks us—points the finger of blame right in our guilty faces.) In “A Short History of Progress,” the anthropologist Ronald Wright declares that humanity is in “ecological deficit”:

“We have financed this monstrous debt by colonizing both past and future, drawing energy, chemical fertilizer and pesticides from the planet’s fossil carbon, and throwing the consequences onto coming generations of our species and all others. Some of those species have already been bankrupted: they are extinct. Others will follow.”

The destructive energies Wright describes have especially flourished in the past thirty-odd years—about the time we entered late-stage capitalism. Every political and ideological system contains at its birth the seed of what will eventually corrupt and destroy it; so maybe we should’ve realized that a system based on perpetually increasing consumption would eventually consume… well, everything.

Over the summer I read “Otherlands: A Journey Through Earth’s Extinct Worlds” by the paleontologist and evolutionary biologist Thomas Halliday. It’s a real page-turner; in each chapter, Halliday travels further back in time, rewinding the planet’s history, over-leaping those five mass extinctions and describing in astonishing detail the startling and entirely alien worlds that preceded our own. The effect is to compel the reader to conjecture what the post-Holocene world might look like—the Earth of a hundred million years hence. Of course we can’t really even begin to guess; all we can say with certainty is that we won’t be anywhere in evidence. Writing in BBC Science Focus Magazine, Luis Villazon has posited that it will take only about ten-thousand years to erase virtually every trace of human civilization from the face of the planet. (An exception is the plutonium-239 in our atmosphere, which will be detectable for at least 250,000 years.)

Life itself will recover and go on, as it always has. The Permian-Triassic extinction killed off nearly ninety-five percent of all species on Earth, but life rebounded in dramatic and unforeseeable ways. Which may sound comforting; yet I think it may be at the root of my own particular fear of mass extinction.

What scares me is that after we’re gone, life may continue—but culture won’t. In the hundreds of millions of years since life emerged on this planet, ours is the only species to invest it with meaning. No other creatures—even those with what might be called intelligence—have ever remotely approached anything resembling agriculture and architecture… music and medicine… law and literature… religion and romantic love… the whole massive edifice of mores and protocols we’ve erected to define, direct and celebrate how and why life is lived. And it seems terrifyingly unlikely that any other species ever will.

That’s all we’ll have come down to, then: a chattering, fractious, messy, brilliant and ultimately momentary spark in the inconceivably long slog of this planet’s super-superannuated existence. A flickering paradox, here for one joyous, sentient whoop, then utterly snuffed out forever.

But there’s always hope (hope being another concept that we invented, and will take with us when we go). Halliday notes that humans “have always been natural ecosystem engineers,” and maintains that if we can summon the will, we can extend our brief stay into something significantly longer—while safeguarding all our nonhuman fellow passengers on Spaceship Earth into the bargain. In other words, if we’re the only species ever to trigger a mass-extinction event, maybe we can be the only species to roll one back.

It’s a worthy alternative to wallowing in fear. But it’s going to take a massive reorientation of our systems, our society and our self-image. On the macro level, that struggle has already begun; but it can be hard to know, on an individual basis, how to help it along.

A humble suggestion? Vote responsibly. And for God’s sake, eat less chicken.