Deep and Ancient Circuits

How might we discern an elephant’s or a mouse’s sense of the world? Elephants and mice might not tell us what they’re thinking. But their brains can. Brain scans show that core emotions of sadness, happiness, rage, or fear, and motivational feelings of hunger and thirst, are generated in “deep and very ancient circuits of the brain,” says the noted neurologist Jaak Panksepp.

Researchers in labs can now trigger many emotional responses by direct electrical stimulation of the brain systems of animals. Rage, for example, gets produced in the same parts of the brains of a cat and a human.

Further evidence of similar experience: many animals respond similarly to mood-altering drugs. Rats can become addicted to the same euphoria-producing drugs that humans get addicted to. Dogs with compulsive behaviors show the same brain abnormalities as humans with obsessive-compulsive disorder; they respond to the same medications. It’s the same disease. And when under stress, other animals’ blood carries the same stress-related hormones that the blood of stressed-out humans does. Crayfish hide for extended periods after getting mild electrical shocks. Such crayfish showed elevated levels of serotonin—evidence of clinical anxiety. When researchers gave the same crayfish a drug commonly used to treat humans suffering from anxiety—chlordiazepoxide—they resumed normal crayfish activities and explorations. The researchers wrote, “Our results demonstrate that crayfish exhibit a form of anxiety similar to that described in vertebrates.”

Having subjected crabs and lobsters to worse treatment than mild electric shocks, I find this discomfiting. Perhaps one could consider administering chlordiazepoxide (or taking some) before throwing the next batch of live crayfish into boiling water. Or try the pasta. Anxiety in many species apparently shares ancient chemical systems largely unchanged during evolution. Makes sense; being afraid of venturing out while danger is lurking has obvious survival value for all kinds of animals.

In experiments, zebra fish, too, can show anxiety in the form of erratic swimming and reduced exploration after acute exposure to caffeine and a kind of hormone (a pheromone) that normally conveys alarm. And fish pain receptors show “remarkable resemblance” to those in humans, writes researcher Cullum Brown. Pain-inducing situations cause “significant activity in the fish forebrain which is highly reminiscent of that observed in humans.” As a fisherman, I’ll admit that people resist the idea that fish feel pain because accepting it dampens the fun that accompanies causing it. One would expect so important a feeling as fear to arise early in the history of animals, and to be retained during evolutionary changes wherever predators may lurk. And that’s what we see. Researchers studying a sea slug named Aplysia conclude that “the functional equivalent of fear occurs in invertebrates and thus may be … widespread in the animal kingdom.” Writes Panksepp, “The resemblances between basic animal and human emotions are truly remarkable.”

But what’s remarkable is that this comes as a surprise to us. What else could we expect?

 

 

Similar emotions arise in so many different life-forms because many complex animals have inherited very ancient emotional systems. The genes that direct our own bodies to create the mood-making brain hormones oxytocin and vasopressin, for instance, date back at least seven hundred million years. They “likely arose when animals became mobile and started to make experience-based decisions,” wrote a team of researchers headed by Isabel Beets of the University of Leuven, in Belgium.

“When a worm is suddenly illuminated,” Darwin wrote, it “dashes like a rabbit into its burrow.” But if you keep scaring it, the worm stops withdrawing. Such apparent learning suggested to Darwin “the presence of a mind of some kind.” Watching as worms evaluated the suitability of objects for plugging their burrows, Darwin offered the idea that worms “deserve to be called intelligent, for they then act in nearly the same manner as a man under similar circumstances.”

Ridiculous? Consider this: “The same neural mechanisms are at work in worms and humans,” wrote S. W. Emmons in a 2012 article with the intriguing title “The Mood of a Worm.” He’s referring to the tiny one-millimeter-long C. elegans—the elegant nematode. (Its genus name is Caenorhabditis, but you can call it C.) Here’s the thing: the worm has nearly the same suite of genes that underlie the nervous systems of humans, giving the worms’ nerves “connectivity patterns also found in the human brain.” C. elegans has just 302 nerve cells. (Humans have roughly 100 billion.) Yet C. elegans produces a motivating chemical similar to oxytocin. The worm’s version is called nematocin, and its function in worms is somewhat familiar. It makes the worms seek sex. Mutant males lacking it spend less time looking for a mate, take longer to recognize one, then initiate copulation more slowly “and execute poorly.” Poor worm! Emmons, who is a professor at the Albert Einstein College of Medicine, leaves us with this insight: “Just as today’s major roads and highways may once have been ancient trails, biological systems can retain essential features derived from their origins.” He cautions, “It is a mistake to consider small invertebrates as primitive.”

Oxytocin drives bonding in monogamous mice (prairie voles, for instance) and monogamous birds (the oft-studied zebra finches and most other birds), and it makes many other species act social or sexual. Block the hormone and they lose interest in socializing, pairing, nesting, and contact with familiar individuals. Oxytocin and opioid hormones create sensations of pleasure and feelings of social comfort in many species, including humans. Given a sniff of oxytocin and then handed their infants, human fathers get more playful with their babies, increase eye-to-eye gazing, and show greater interest in the child. The father’s attention in turn sparks the infant’s brain to release an oxytocin boost. This is the chemistry of bonding.

When we do something that we know is a bad idea, it’s often because hormone-flooded ancient parts of our own brains disable our intellectual override switch. Hormones can unlock—for instance—the cages that contain deep sexual feelings, setting loose behaviors we become powerless to resist, leaving rationality temporarily bound and gagged while emotions hijack our minds. Sex is often so risky and costly that we might never reproduce if our brains weren’t chemically sparking urges for obtaining our next fix. It sounds quite animal, doesn’t it? And it feels that way—because it is. It so deliciously, so frighteningly is.

Back in 1883, George John Romanes, writing Mental Evolution in Animals, recognized that “whether we meet with nerve-tissue in a jelly-fish, an oyster, an insect, a bird, or a man, we have no difficulty in recognizing its structural units as everywhere more or less similar.” Sigmund Freud observed that the nerve cells in a crayfish were basically the same as the nerves in human beings. Freud grasped that the nerve cell is the signaling unit of the animal nervous system. As Oliver Sacks explains, neurons “are essentially the same from the most primitive animal life to the most advanced. It is their number and organization that differ.”

 

 

So when Vicki said, “We all have the same basic brain,” she almost literally opened a can of worms. What if other animals actually do feel even a few of the sensations that in humans we label with words like uncertainty, anxiety, worry, pain, fear, terror, defiance, defensiveness, protectiveness, anger, disdain, rage, hatred, distrust, disappointment, reassurance, patience, persistence, interest, affection, surprise, happiness, delight, joy, exuberance, sadness, depression, remorse, guilt, shame, grief, awe, wonder, curiosity, humor, playfulness, tenderness, lust, longing, love, jealousy, loyalty, compassion, altruism, pride, vanity, shyness, calm, relief, disgust, gratitude, abhorrence, hope, modesty, sorrow, frustration, fairness—

Is it possible that humans alone feel all these things, that other animals feel none of them? I don’t think so. We wouldn’t be projecting human feelings if we correctly perceived their feelings. But if we deny the possibility that they have feelings, and they actually do have feelings, we’d have been wrong. I think we’ve been wrong in exactly that way. I’m not suggesting that humans and other animals have all the same emotions. Self-loathing seems uniquely human.

So we needn’t be so fearful that we might mistakenly project the emotion of, say, fear. Certain seabird and seal species have lived for millions of years on oceanic islands hundreds of miles from the predatory mammals of continental shores. Safely distanced from those predators in miles and in time, the seabirds and seals lack the ability to fear mammals. They cannot acquire needed fear when rats, cats, dogs, and people arrive by boat. Then their absence of fear becomes painfully obvious. Nesting albatrosses sit still as rats literally gnaw them to death. They did not fly or run as people clubbed them by the millions for their feathers.

On the other hand, continental animals with a long history of being hunted by humans, fully capable of fear, relax in places safe from hunting, such as national parks. In suburban neighborhoods, animals that are usually shy—ducks, geese, deer, turkeys, and coyotes—can be calculatedly brazen. Canada geese barely move out of the way of people on foot on the campus where I work. But on a river in northern Quebec, traveling with Cree people who love to eat geese, I got only fleeting glimpses of goose rear ends as we rounded river bends and they fled the sight of us. In African parks, lions have learned that they may safely enjoy the shade of vehicles full of tourists. Cheetahs sometimes even hop up on vehicles for a more commanding view of potential prey. Elephants can be fearful, aggressive, or nonchalant around humans, depending on what they’ve learned to expect. My point: when animals are fearful, we easily see that. When they lack the emotion of fear, we can easily see that, too. We don’t make those mistakes. Rather than mistakenly attributing emotions that they do not experience, we have made a larger mistake by denying emotions that other animals do experience.

 

 

So, do other animals have human emotions? Yes, they do. Do humans have animal emotions? Yes; they’re largely the same. Many animals feel and show fear, aggression, well-being, anxiety, and pleasure. Those are the emotions of shared brain structures and shared chemistries, originated in shared ancestry. They are the shared feelings of a shared world. An elephant approaches water anticipating the relief of refreshment and the pleasures of mud. When my puppy rolls on her back to prompt me to rub her belly—again—it’s because she anticipates the soothing experience of our warm contact. Even when my dogs aren’t hungry, they always enjoy a treat. They enjoy a treat.

The problem isn’t “imposing … a distinctly human understanding of the world.” The problem is imposing a distinctly human misunderstanding. The human understanding that we can bring to bear is our deepest insight into the living world: all life is one. Their cells are our cells, their body is our body, their skeleton our skeleton, their heart, lungs, blood, ours. If we impose that distinctly human understanding, we’ve taken one giant stride in seeing, truly, each species within the vast, continuing living venture. Each species is a distinction on a continuum, like notes on a violin’s fingerboard. There for the finding. Fretless. No abrupt breaks. And quite a symphony.