As Soon As Humans Learned to Cooperate, We Started Making Species Go Extinct

Few species have been as adept at making other ones go extinct as we humanfolk. Over the centuries, we've had a hand in wiping out enough species to fill a flood-bound ark or two. But new research shows that we've been knocking off mammals before we even evolved into modern man.

We've been at the eradication game for two million years, it turns out, driving mammals extinct en masse long before we became Homo sapiens. So what made our forebears do it? A taste for meat—and an ability to obtain it, thanks to the fact that we'd recently learned to cooperate.

"In my studies of the fossil record of African carnivores, I have found that lions, hyenas and other large-bodied carnivores that roam eastern Africa today represent only a small fraction of the diversity this group once had," writes Swedish paleontologist Lars Werdelin in Scientific American. "Intriguingly, the decline of these carnivores began around the same time that early Homo started eating more meat, thus entering into competition with the carnivores. The timing of events hints that early humans are to blame for the extinction of these beasts."

Previously, it was believed that climatic changes had driven many of these animals to a prehistoric mass grave. But primitive man might have done it themselves, by learning to team up against the massive predators. I reached out to Dr. Werdelin, and he explained how we drove so many classically ferocious creatures to the brink. First off, it wasn't hunting.

"Instead, this is about two things: social behavior and scavenging," he said. "The first is readily summarized as 'strength in numbers.' Twenty individuals with sticks would be a more formidable foe than one individual with a rock. Thus, social behavior and cooperation would have allowed our early ancestors to appropriate carcasses from carnivores, either by getting to them first or by driving the carnivores away, neither of which would have been likely without cooperation, and therefore not available to our ancestors prior to early Homo."

It was the moment that we started teaming up that we were able to start doing some damage—before humans started hunting big game with spears and other weapons.

"By this means, early Homo could drive specialized large carnivores to extinction by dominating their food resources, which would have been crucial, especially during the dry periods of the year when food was scarce in general," Werdelin said.

During those first couple million years that constitute the dawn of humanity, we were small-brained, plant-feeding, ape-like, and vulnerable. As our brains grew, so did our ability to cooperate. We got better at scavenging—using stone tools to carve out carcasses more quickly and efficiently and teaming up to scare off the competition.

As many as ten species of carnivores were killed off by team humanity—the first of what is now a long and ever-lengthening list of victims. That's not all that many—but keep in mind that there are just a handful of species in their size bracket alive today, Werdelin told me.

"Not only did individual species die out, but entire groups of species, such as the sabertooth cats, disappeared," he said. "As these beasts of yore declined, modern species—including the lions, leopards and jackals that inhabit Africa today—came to account for an ever increasing proportion of carnivore communities. By around 300,000 years ago the archaic carnivore lineages had all been winnowed out."

Now, obviously, man is not the only species extinguisher in history. Far from it. There were the early cyanobacteria, the original mass-killers, whose oxygen-spewing photosynthesis habits ended up exterminating just about every anaerobic organism on earth two and a half billion years ago.  And competition results in a never-ending chain of extinction, with an incomprehensible number of animals dying off throughout natural history. Animals kill other animals kill other animals and so on, at least until our sun goes supernova and pulls our dying planet into it.

But here's the difference. Unlike our early ancestors, we know we're on the warpath. Thanks to the propensity for abstract thought, we are capable of recognizing that our team has gotten a little out of control. We have gotten so good at teaming up to conquer the planet's harsh vagaries that we are killing a lot more than big game—many scientists claim that our dominance is so complete that we are currently spurring the sixth major extinction event.

We have created such an intricate network of mining operations and power plants and development projects and food harvesting efforts that today's species don't stand a chance. They are going extinct somewhere between 1,000 and 10,000 times faster than the background rate. Dozens are dying off every day.

So what's the link between those first species to perish at our hands, and the the hundreds we're currently wiping out every year?

"My take on this based on my work, is that it is natural for us to both kill other mammals and to exploit available natural resources as best we can. We've been doing it since the first day we were able to. There is no shame in the act," Wederlin said. "However, we have tools now that allow us to do these things so much more efficiently than in the past, and (obviously) knowledge that we didn't have 2 million years ago about how the environment is affected by our activities. The shame lies in not acting on this, and in not helping others to do the same (e.g. ensuring that poachers in Africa do not need to kill elephants and other endangered animals to make a living)."

Which leaves us at an interesting juncture. We're the only species in history that could decide whether or not to prevent a mass extinction. Or can we? Even though we're hardwired to thrive at any expense, Wederlin thinks achieving a sustainable balance with our co-species is possible.

"It is natural for us to do these things, but we are capable of rising above our natural instincts."