Two Ends of the Same Leash

Let’s raise the stakes. We’re going to move from dogs to apes.

With no training, chimpanzees can cooperate to pull ropes together to retrieve a heavy box of food. But they seldom do. They have a problem. The problem is: they can be their own worst enemies. Chimpanzees will not cooperate on rope pulling unless: (1) the food can be shared, (2) the partners cannot reach each other, and (3) the partners previously shared food. If those criteria aren’t met, chimpanzees will not cooperate. The reasons: subordinate chimpanzees won’t risk attack by dominants, and dominants can’t seem to control their aggressive impulses towards subordinates who are getting some food—even if by not cooperating, the dominant one doesn’t get any food, either. They can’t cooperate even when cooperation is actually quite selfish. “Be nice, and everybody eats” is too much to ask of a chimpanzee.

 

 

Chimpanzees lack dogs’ human-like skills because chimpanzees lack dogs’ human-like cooperative tendencies. We know dogs got it as wolves. But where on Earth did the human-like temperament of humans come from?

Some researchers believe that early humans had to evolve a conciliatory, friendly, human-like temperament before communicative and cooperative behaviors could offer such enormous advantages.

Well, if the advantages are so great, why haven’t chimpanzees evolved a conciliatory, friendly, human-like temperament? Some, it seems, did. And this is constructive for considering humans. Ever wonder why, when chimps are often so nasty, bonobos are so friendly and sexy with one another? Self-domestication seems to be the answer. Bonobos, like wolves, seem to have self-domesticated. More remarkably in the bonobo case, their self-domestication had nothing at all to do with humans. Bonobos evolved after the Congo River formed, about a million years ago, isolating a population of chimpanzees south of the river. Somehow, for the bonobos, a lot changed.

As chimpanzees reach adulthood, they become less playful and largely intolerant of sharing. Bonobos are like chimps who never quite grow up. Adult bonobos play with each other the way juvenile chimpanzees play with each other. Bonobos famously indulge in copious sex play and nonreproductive sexual behavior. This sexiness with one another greatly dissipates tensions, boosting food sharing and cooperation and friendly meetings between groups. In the same setup where chimpanzees could not overcome their aggression to cooperate in pulling ropes to access a treat-filled box, bonobos played, foreplayed, and happily shared the food like youngsters. “Adult bonobos,” researchers commented, “performed at the level of juvenile chimpanzees.” If, compared to their warmongering, covetous, political chimp cousins, bonobos sound like kids playing and being cooperative—that’s the point.

Chimpanzee between-group encounters are always tense and can at times be warlike. For males caught without their group’s support, such encounters sometimes turn lethal. And males sometimes kill babies of other groups. In contrast, bonobos meeting strange groups of bonobos often just backtrack into their own territories. But sometimes bonobo groups mingle, flirt, and frolic, using the opportunity for a social call of grooming and horsing around. And if the mood is right, they may indulge in a polite—though, by chimpanzee standards, wildly promiscuous—orgy.

Chimps are jealous, ambitious, frequently aggressive within their own group. Chimpanzee groups are male-dominated. Male chimps form coalitions against other males, and dominance is mainly about monopolizing fertile females (result: dominant males achieve disproportionate fatherhood; this is the main advantage of their aggressive, status-seeking side). A bonobo group’s dominant individual is never a male, always a female. Female coalitions dominate, preserve the peace, and keep males socially submissive. Female authority dampens male aggression.

A male bonobo’s closest lifelong bond is to his mother (as in killer whales). Fights are rare, and various sexual combinations often settle disputes. Females choose whom they wish to mate with and when—and they’re not very choosy. Females prefer belly-to-belly copulation and often initiate sex—things that self-respecting chimp females would never think of doing. Bonobos, it might be said, are trisexual; they’ll try anything with anybody. Sharing is caring. Many males in the group sire similar numbers of young.

Were the chimpanzee ancestors of bonobos who found themselves newly cut off on the south side of the Congo River a small group with mostly females? Even so, how would female dominance and leadership become institutionalized? Mysteries.

As in all of us, bonobo personality parameters are brain-related. Compared to chimpanzees, bonobo brains have more gray matter in regions involved in perceiving distress in others. Bonobos have a larger nerve pathway for controlling aggressive impulses, inhibiting harm toward others. This limits stress, dissipates tension, and reduces anxiety to levels that open up room for sex and play.

Even as adults, bonobos have brain hormones and blood chemistries typical of juveniles, including higher levels of serotonin, which suppresses aggression, and lower stress hormones. Brain chemistry typical of juveniles prompts juvenile behaviors such as playfulness, friendliness, and trust. The underlying genetic changes result in a suite of behavioral, internal, and physical features. For instance, compared to chimpanzees, bonobos mature more slowly physically, psychologically, and socially, and they learn skills more slowly. The same genes that lower aggressiveness by creating a more juvenile-like brain chemistry also create more juvenile physical features. An adult bonobo’s skull looks like an adolescent chimp’s. More to the point, an adult bonobo’s skull looks like a juvenile bonobo’s skull. Their heads are more like juveniles’ heads in shape and size, and bonobos have smaller canine teeth (20 percent smaller than male chimpanzees’). Compared to chimps, bonobos have smaller jaws in flatter faces. Female chimpanzees lose the labia majora as they mature; bonobos, like humans, retain them into adulthood. Female bonobos’ clitoris and genitalia are situated more toward the front than are chimpanzees’, helping explain their preference for the missionary position. Bonobos have lost their lip pigmentation; they have fetching pinkish lips.

Why and how bonobos self-domesticated is still not clear, though there’s an intriguing possibility that relates to bonobos having wandered into a sort of food-filled Garden of Eden. That’s a bit of an exaggeration, but food abundance might be the difference. Adult chimpanzees can remember many more places where they’ve seen food hidden than can bonobos, suggesting that food for chimps is scarcer and requires more searching, more skills, and more work. And in fact, bonobos forage for shorter periods of time, over smaller areas, and in larger groups than do chimps. No gorillas live where bonobos live. So to the limited extent that gorilla and chimpanzee foods overlap, there’s more food for bonobos in their gorilla-less domain. Fights between chimps can result in serious injury or death. Chimps often forage at some distance from one another, and females spend significant time alone. Bonobos’ more concentrated food supply facilitates larger foraging groups. So it seems that bonobos had to deal with the tensions and friction caused by closer, more frequent contacts. This necessitated a capacity for more peaceful interpersonal relationships. Somehow, bonobos achieved this, almost completely liberating themselves from violence.

Primate expert Richard Wrangham describes bonobos as “chimpanzees with a threefold path to peace. They have reduced the level of violence in relations between the sexes, in relations among males, and in relations between communities.” Japanese primatologist Takeshi Furuichi, the only person who has studied both free-living chimps and bonobos, observed succinctly, “With bonobos everything is peaceful. When I see bonobos, they seem to be enjoying their lives.”

 

 

“Following this line of reasoning,” say Brian Hare and Michael Tomasello, sounding very cautious as they tiptoe into a suggestion: “one might seriously entertain the hypothesis that an important first step in the evolution of modern human societies was a kind of self-domestication.”

How’s that? Hare and Tomasello, recalling those Russian foxes in which only the friendly ones survived to breed, speculated that humans “either killed or ostracized those who were over-aggressive or despotic. Thus, like domestic dogs, this selection for tamer emotional reactivity put our hominid ancestors in a new adaptive space,” preparing the ground for evolution of “modern human-like forms of social interaction and communication.”

Well, killing the overly aggressive doesn’t sound too friendly. But isn’t that the whole history of democracy and the struggle for human freedom and dignity? And today don’t we give governments the job of killing, and isolating the overly aggressive among us by putting them behind bars? Aren’t we, by fits and starts, even through the darkness of unspeakable human horrors, always searching for peace, always seeking more perfect ways of taming ourselves? Self-domestication does indeed seem part of the human program. The process of becoming more civil is called civilization.

I’ve long thought that humanity seems to be in a juvenile phase, and have assumed that we were somehow on a trajectory of maturation. If the self-domestication idea is correct, it means that we are in a juvenile phase, but that we’re going in an increasingly infantilizing direction.

The juvenile traits of adult humans are so apparent that as early as 1926 one scientist summed us up this way: “If I wished to express the basic principle of my ideas in a somewhat strongly worded sentence, I would say that man, in his bodily development, is a primate fetus that has become sexually mature.”

 

 

Experimental foxes, our family dogs, and free-living bonobos all show that along for the ride with a genetic predisposition for friendliness come other incidental, unselected changes programmed into the same stretches of DNA. Turns out that in all domesticated animals a bundle of things accompany a tamer, human-caused life. Over many generations of domestication, most mammals (cows, pigs, sheep, goats, even guinea pigs) actually got smaller, with slenderized skeletons compared to those of their more robust free-living ancestral relatives. Typically the skull’s brain case becomes smaller, as does the brain itself. The muzzle shortens, causing relative flattening of the face. This creates tooth-crowding problems; teeth themselves become smaller. Size differences between males and females narrow. Hair colors and textures diversify. Fat-storage capacity increases under the skin and in muscle. Activity decreases, and docility increases. Breeding seasons lengthen, along with increases in courtship behavior, sexual stimulation, nonconceptive sexual behaviors, multiple births, and milk production. Juvenile behaviors, including play and low levels of male aggression, extend into adulthood.

During domestication, dogs lost as much as 30 percent of their brain size relative to body weight compared with wolves. Pigs, ferrets, about the same; minks, about 20 percent; horses, about 15 percent. Domestic animals gone feral don’t regain brain size, showing that the loss is indeed genetic. Compared to their wild progenitors, domestic guinea pigs are less interested in aggression, more interested in sex, and pay less attention to the environment around them. Genetic changes that alter the endocrine system drive domestic animals toward such differences.

 

 

In the Late Pleistocene, numerous similar physical changes also appeared in some human populations. Let’s consult the human fossil record. Though we tend to assume that civilization made humans larger, earlier humans actually shrank. By about 18,000 years ago, the shrinkage totaled a considerable four inches (ten centimeters) of height in Europe. This trend toward diminishment continued during the transition into agriculture. Climate warming can probably be ruled out as a reason for shrinking. Humans tend—with notable exceptions—to respond to warm climates over evolutionary time by getting taller, because in us, longer limbs increase cooling capacity. This suggests that some other transformation was causing human shortening. (Improvements in health and nutrition over the last 200 years have again made Europeans as tall as their Paleolithic ancestors.)

Other changes came as humans attained our modern looks. Compared to Neanderthals, the first modern humans, at 130,000 years ago, “had much smaller faces,” according to American anthropologist Osbjorn Pearson. At the end of the Pleistocene, certain human groups and their associated animals begin progressively to show parallel reductions in size and stature, shortening of the face and jaws, tooth crowding, and reduced tooth size. Pearson says that size reduction of our face and teeth began during the long process toward settled living.

Experts debate whether human brain size relative to body weight has declined. But regardless, we have smaller brains than did Neanderthals. Australian males in both sedentary and nomadic populations, for example, underwent a 9 percent decline in skull volume from the Pleistocene to our present epoch, the Holocene. By roughly 12,000 years ago, such changes characterized nearly all humans. Our modern brains, with a volume of about 1,350 cubic centimeters, are ten percent smaller than the 1,500 cubic centimeter

 

 

Animals under early domestication received shelter, a diet altered by agriculture, and protection from predators through relative confinement. This reduced their sensory needs, facilitating further domestication. As our domesticated animals settled in for a life of reduced activity and stimulation, so did humans. As people provided safer, more sedentary conditions for their livestock, they did the same for themselves. The confinement was mutual. By moving out of nature and settling onto farms, we became in a real sense just another farm animal. Caltech brain researcher John Allman says that through agriculture and other ways of reducing daily hazards of existence, humans domesticated themselves. We now depend on others to provide food and our shelter. We’re a lot like poodles in that regard.

Domestic creatures don’t need to live by their wits. It behooves them to be accepting of their lot, not uppity. Cows and goats don’t seem very alert to their surroundings; they don’t have to be. And neither do the people who keep them. Archaeologist Colin Groves writes, “Humans have undergone a reduction in environmental awareness in parallel to domestic species and for exactly the same reason.” He explains that domestication is a kind of partnership in which “each partner is, to a degree, sheltered by its association with the other.” Groves says security has cost us a certain dulling of senses, explaining that brain changes have caused in humans “the decline of environmental appreciation.”

I find that statement arresting. He uses the word “environmental” to mean our total surrounding environment. But I think, too, about our awareness of the natural world. “To speak truly,” observed Emerson long ago, “few adult persons can see nature. Most persons do not see the sun.”

I always thought humanity’s alienation from nature was just a habit. Clearly, there have recently been tribal hunter-gatherers living in close resonance with the living world. Yet what if the problem of alienation from nature—the idea of the banishment from the Garden—is embedded into real human nature? Is ours a human nature altered by self-domestication? Have we been domesticated by our own domestic animals? What if “domestication syndrome” is human nature?

Robinson Jeffers:

 … the race of man was made

By shock and agony …

 … they learned to butcher beasts and to slaughter men,

And hate the world.

 

 

So: did the changes we imposed on ourselves in the process of settling into our civilizing “domesticity” really bring to humans changes in fat storage, sexuality, frequency of multiple births, declining sensory abilities, flatter faces with crowded teeth, and docility similar to those we see in other domestic animals?

What is certain: our view of ourselves as postevolutionary, purely cultural creatures, standing outside of selective pressures and in control of our fate is wrong. We tend to think that humans evolved, then stopped evolving and started culture. Far from it. The onset of agriculture and the flowering cultures of civilization were themselves enormous changes in the human environment, massively altering selective pressures. Pressures to maintain a hunter’s size and strength and senses relaxed, while pressure to behave cooperatively, expand social skills, and suppress violent urges intensified. Small, slender, thin-boned people might not have excelled at the rigors of mammoth hunting. But people requiring fewer calories might have survived better during crop failures. Darwin coined the term “natural selection” because he was comparing the mechanics of what happens in nature with the artificial selection applied in raising livestock. But nature doesn’t really select; it filters. The environment works as a filter, and as the environment changes, it filters differently. The point is: as the pressures change, we remain a work in progress.

Look at the evolving creature in the mirror. Realize that we’ve got a ways to go before we’re universally as good to each other, or as much fun with one another, as are bonobos.

 

 

It’s been said that no two species are more alike than wolves and humans. If you watch wolves not just in all their beauty and adaptability but in all their brutality, it’s hard to escape that conclusion.

Living as we do in family packs, fending off the human wolves among us, managing the wolves within us, we can easily recognize in real wolves their social dilemmas and their status quests. No wonder Native Americans saw wolves as a sibling spirit.

Consider the similarities between male wolves and men. They’re quite striking. Males of very few species directly enhance the survival of females or young year-round. For example, most male birds provide food to females and young only during the breeding season. In a few fishes and a few monkey species, males actively care for young, but only while the young are small. Owl monkey males carry and protect babies, but they don’t feed them. Male lemurs challenge predators, allowing females to escape, but they don’t provide any food.

Helping procure food year-round, bringing food to babies, helping raise young to full maturity over several years, and defending females and offspring against individuals who threaten their safety is a very rare package to find in a male. Human males and wolf males—that’s about it. And of the two, the more dependably faithful isn’t us. Male wolves more reliably stick with the program, helping raise young and actually helping females survive.

Chimpanzees seem much closer to humans, but male chimps don’t help feed babies or bring food back to a home site. Wolves and humans can understand each other better. That’s one reason why we invited wolves, instead of chimpanzees, into our lives. Wolves and dogs and us; it’s not surprising that we found each other. We deserve one another. We were made for each other.

 

 

In our kitchens, on our floors and sofas, in our laps and in our beds, hidden in plain sight among humans who’ve forgotten the ancient origins of our eager pets, wolves in dogs’ clothing riddle our homes and transform our families and our hearts, wagging their sweet tails, being our working partners and best friends. It’s not as ironic as it might seem that a creature as violent as a wolf could domesticate itself into humanity’s most beloved companion. They could say something similar about us. In the form of their dog avatar, wolves mesh with humans through their astute, innate grasp of in-group, out-group living. A wolf knows who to protect and who to attack and how to defend to the death. That obsession for distinguishing friend from foe is one we share. It’s why we understand one another, on the one hand, and fear one another, on the other hand. It’s why since deep antiquity we have viewed wolves as everything from guards to gods.

To watch wild wolves is to recognize a kindred creature by turns riveting, horrifying, and admirable. It’s also to see how many of our dogs’ tendencies and talents were fully formed in the wild, and remain intact in our homes.

Dogs have been diversified into an enormous range; think of Great Danes and Chihuahuas. Yet even at a distance, a dog seems to recognize the difference between another dog—no matter what the breed—and a cat. And so do children.

Rick McIntyre likes to tell people that because many households have dogs, we already “know about both.”

“You mean both wolves and dogs? Or both wolves and humans?” I ask.

“Right,” he says.

 

 

“Does my dog love me, or does he just want a treat?” A professor who is an expert in climate change—not dogs—recently asked me that question. I’ve often asked it myself. Short answer: your dog really does love you. Part of the reason is: because you are kind. If you were abusive, your dog would fear you. And they might still love you, out of duty or need—not so different from many people trapped in abusive relationships. But to answer the question directly: what we know about dogs’ brains, their brain chemistry, and the changes to their brains caused by domestication tells us that yes, your dog loves you. A dog’s ability to feel love for humans comes partly from the love wolves have for wolves, partly from the genetic changes of their domesticated ancestry. In dogs, we’ve bred the people we wish we could be: loyal, hardworking, watchful, fiercely protective, intuitive, sensitive, affectionate, helpful to those in need. No matter how they originated, their feelings are real to them. Your dog genuinely loves you, as you, in your domesticated state, activating the deep, old parts of your brain, love your dog.

 

 

Just outside Bozeman, Montana, Chris Bahn and his wife, Mary-Martha run a bed–and-breakfast called Howlers Inn. On four fenced acres right next to their home, they provide for several captive-born wolves who needed a haven. Chris and Mary-Martha had raised these wolves by hand, bottle-feeding them from the age of three weeks. They’ve known no other life. They are real wolves, not wolf-dog hybrids. When I drove up, they came to the fence like dogs, curious.

Having read about the Russian friendly foxes with the curly tails and theories that friendly wolves domesticated themselves—which all made perfect sense—I was nonetheless unprepared for the first time I saw a man interact with tame, undomesticated wolves.

When Chris entered the enclosure, he was wearing a canvas jumpsuit to protect himself from the enthusiasm of their surprisingly long and sharp claws. What surprised me most, though, was their doglike friendliness. They were wagging their tails, happily rallying round him. (I had to remain outside.)

“Wolves are extremely expressive,” Chris said, looking up at me while kneeling in a sea of swarming wolves. “Probably even more so than dogs. You always know what a wolf is thinking, whether they’re happy or relaxed or uncomfortable.”

The alpha male, aged six, came for vigorous rubs and then rolled belly-up. Chris crouched down and obliged, while others gave him licks to the face, just as Jude likes to do while I’m rubbing Chula’s belly at home. I asked Chris where he is in the pack order. He says he’s not; he has no dominance role. His role is caretaker.

Seeing these wolves, I found it perfectly plausible that wolves who’d acquired a habit of hanging around human habitations began to hold dual citizenship and then, as centuries came and went, started to integrate into the human social lattice, departing from their origins. It would have been a good career move.