Even though you are reading this on a sophisticated electronic device, you are an animal. That's the most radical idea to come out of Charles Darwin's groundbreaking studies of evolution, and even today, it still freaks people out.
Photo by Carleigh, via Humans Hugging Dogs
I know this because last week I wrote an article about all the pieces of evidence that suggest humans have become domestic animals , which I thought was a fairly non-controversial claim. Among evolutionary biologists, it certainly is. Just as agriculture and a sedentary life have changed the genomes of dogs, cows, sheep and chickens, they have also changed ours. But after the article posted, many people responded to say that they didn't like my casual use of the phrase "domestic animal" to describe Homo sapiens.
But what else would we be? Are we exempt from the same forces that have changed our fellow animals on farms and in cities? Does a sedentary, domestic life behind walls exert evolutionary pressures on sheep and pigs, but not on humans? If you accept the precepts of evolutionary theory, where environmental pressures drive natural selection, obviously not. Environments are environments, regardless of whether we built them or not.
Indeed, environmental scientists even have a word for the domesticated natural habitats that humans have created: agroecosystem.
Leaving aside religion, there are two main objections to the idea that humans are animals. One comes from environmentalists who believe that humans are unique in their ability to fuck up the planet, not to put too fine a point on it. The other comes from a common sense notion that humans are so different from all the other species out there that we might as well be a different order of being altogether.
Let me explain why both are utterly wrong.
First of all, humans are not the first species ever to transform the planet into a polluted hellhole. That honor belongs to cyanobacteria, blue green algae that evolved about 3.5 billion years ago and promptly began to fill the methane-based atmosphere with oxygen. You see, oxygen was a byproduct of a new energy-making system that cyano had developed . We call it photosynthesis — it's the way all plants today make energy out of light and water. At the time, however, all the life forms on the planet had evolved to live in a methane-rich environment. As the cyano filled Earth's atmosphere with oxygen, their nasty byproduct attenuated the methane, killing off pretty much all the other life forms around them. We may love our nicely oxygenated air today, but at the time it was an apocalypse. It's also evidence that humans aren't the only species ever to change the atmosphere with a new form of energy production.
We also aren't the only species to change land uses for our own ends. Beavers build dams that utterly transform the way water moves through forests, flooding some areas and parching others. Ants build massive underground cities, full of farms where they "milk" aphids for food and grow fungus to eat. So we are not the only polluting life forms, and we are not the only ones to transform landscapes with building and farming.
Finally, we aren't the only species to spread all over the planet either. Humans share that honor with other invasive species, including extinct animals like trilobites, as well as living ones like rats, crows, cockroaches and more. Invasive species have roamed across the Earth since life began. Humans are about as special as dirty little rodents, scampering between walls in search of some garbage to eat.
But what about the fact that humans are undeniably different from all other species that we've met so far? We've got this whole written language thing going on, plus we build rockets and suspension bridges and indoor plumbing (which — thanks, humanity!). It's true. Just like every other creature on the planet, we have our special norms and rituals. Part of what makes us animals is the fact that we have unique behaviors that we can call our own.
Yet we have many other behaviors that we share with our fellow animals. Darwin wrote about this in one of his lesser-known works, The Expression of the Emotions in Man and Animals. Today, hundreds of scientific studies have offered solid evidence that animals from chimps to rats share the same kinds of emotions and motivations that we do.
Many animals also make tools the way humans do too. We've long known about tool-making among other primates, but recently scientists have found evidence of tool-use among dolphins, crows, and even sea otters.
Humans may not use tools and express emotions exactly like other animals, but that doesn't exempt us from animal status. No two species share exactly the same sets of behavior. But we also share far too much in common to pretend that we are some form of life that transcends animal status.
The real question we should be asking ourselves is what we gain by claiming that humans are not animals. Does our special status make us seem more powerful than we are? Does it make our lives more meaningful? Does is allow us to justify our behavior toward other life forms?
The famous anthropologist Clifford Geertz once said that he believed "man is an animal suspended in webs of significance he himself has spun." Ultimately, the only animals who buy the idea that humans aren't animals are humans themselves.
Annalee Newitz is the editor-in-chief of io9, and this is her column. She's also the author of a book called Scatter, Adapt and Remember: How Humans Will Survive a Mass Extinction.