by Ted Kerasote
All plant and animal cells contain mitochondria. These tiny bodies are found outside the cell nucleus, in the cytoplasm, and mix calories and oxygen to produce energy. We then use that energy to read this page, to throw a ball, and, if you're a dog, to fetch it.
What's important to know about mitochondrial DNA, or mtDNA for short, is that it's a powerful search engine. Unlike the DNA in our chromosomes, which we inherit from both our parents, mtDNA is received only from our mothers. By tracing the occurrence of mutations back through time—in the DNA of living people as well as in that harvested from skeletal remains—geneticists have been able to determine how long ago two matrilineal clans diverged, in other words, when someone's maternal ancestors shared common mutations in their mtDNA and when they didn't. By calibrating these divergences with fossil remains of known ages (calculated by the radioactive decay of the isotope carbon-14), scientists have then been able to create what are called "molecular clocks." This sort of analysis has led geneticists to conclude that everyone alive today is related to one woman—dubbed "mitochondrial Eve"—who lived in Africa about 150,000 to 175,000 years ago.
Robert K. Wayne applied these techniques to dogs. He looked at 162 wolves from 27 locations around the world and compared the sequences of their mtDNA to that of 140 domestic dogs, representing 67 breeds. For good measure, he also sequenced five coyotes and twelve jackals. The results were stunning: Merle, the Khyi, the dog lying on your bed as you read this, in fact, every domestic dog alive today, during the last century, and going back for thousands upon thousands of years, from the smallest Pekingese to the largest Great Dane, is descended from wolves.
That's not to say that some coyote or jackal genes, here and there over the ages, haven't found their way into domestic dogs, since these wild canids can interbreed with wolves. Yet, as Wayne has stated, "Dogs are gray wolves, despite their diversity in size and proportion." What's more, Wayne's research showed that dogs could have been domesticated as long as 135,000 years ago.
At the time Wayne published his research, 1997, the oldest fossils of domesticated dogs had been dated at between twelve thousand and fourteen thousand years old. His findings therefore made everyone sit up and take notice. In fact, many scientists expressed skepticism about his date, saying that the randomness of mutations creates large variances in the reliability of molecular clocks. These variances could make Wayne's 135,000-year figure off by as many as tens of thousands of years. Even with that much wiggle room, however, his date for the domestication of dogs still fell roughly within the window of time during which the ancient people to whom we're all related left Africa and reached lands where wolves lived. There were no wolves in Africa at this time.
Because no written records exist from this period, nor even any oral histories, we will probably never know whether a wolf really walked into a circle of people sitting around a campfire, stared into the eyes of someone whose sweat smelled of reconstituted gazelle, and said, "I'm your dog." There are enough clues, however, to suggest that the domestication of wolves occurred in two different ways. The first hypothesis argues that we tamed wolves quite early on in our history while we were still hunter-gatherers; the second that wolves tamed themselves rather late in our history, as we settled in villages about twelve thousand years ago and were in the process of becoming farmers.
Both theories rely on the phenomenon known as "flight distance," a term that describes how close wildlife will let a person (or another potentially threatening animal) approach before fleeing. Even within the same species, flight distance varies among individuals. Some animals are nervous of humans and keep their distance. Some are indecisive—unsure whether to approach or flee. And some are bold, coming close to satisfy their curiosity and maybe to seek a handout. Anyone who visits a city park can see flight distance in action. Those geese and squirrels who have been fed, and haven't been harmed, will lead their offspring close to people. Those who have never learned the behavior, or who have narrowly escaped being snagged by a homeless person for dinner, will not. In any given batch of offspring, however, there are always going to be some individuals who are congenitally more or less cautious than their siblings. These factors are part of the broader discussion about which factor has the most effect on an individual—nature or nurture, what we inherit or what we learn.
When it comes to the ancestors of domestic dogs, both factors had to be operating. There were some wolves who were congenitally more curious, a bit more willing to take a risk and see what was up with those unusual bipedal creatures. Some of those wolves were immediately speared or arrowed, or got the fright of their lives in return for their curiosity; others managed to snatch a scrap of meat or a bone from a carcass. Eventually, these wolves learned to associate loosely with a band of humans, tracking their kills and scavenging them. In the meantime, the human hunters tracked the kills wolves made and, likewise, scavenged them.
At the heart of this relationship was energy conservation, a principle still operating today. If you can buy exactly the same groceries at a nearby store as at one five miles away, you'll shop at the closer location. If wolves could pick over a deer killed by humans, and supply themselves with extra calories, they would. If humans could scavenge a deer killed by a wolf pack rather than kill one themselves, they would, too. Such alliances were matters of convenience. Admiration, and love, came later.
Among this pool of wolves with short flight distances, some were especially willing to get close to humans. This wasn't an expression of friendliness, but of stress. Such a wolf could have been a female who had lost her mate to an accident and was thus unable to provide enough food for her pups. Left alone in the den while their mom hunted and scavenged, these pups would also have been the very sort of wolves who were first stolen by humans. After all, what could be more fun, if you were a young person growing up without a Game Boy, than to bring home a roly-poly wolf pup to play with?
Most of these pups were going to be too shy or already too mature—too imprinted on other wolves—ever to become domesticated. But some were going to be young enough and have just the right mixture of genes that would predispose them to live comfortably among people.
An example of how these events may have taken place was documented by Adolph Murie in his 1944 study The Wolves of Mount McKinley. Murie was a U.S. Fish and Wildlife Service biologist sent to Alaska on what today seems an almost unbelievable mission: to determine whether the American government should allow wolves to continue to exist in Mount McKinley (now Denali) National Park or exterminate them.
From 1939 to 1941, Murie watched a wolf family on the park's East Fork River—seven adults and five pups—and their interaction with Dall sheep, caribou, moose, grizzly bears, and other wildlife. On May 15, 1940, Murie took a pup from the pack's den so as to familiarize himself, as he put it, "with wolf character." The pup was a dark furry female, so young that her eyes were still closed. Unable to walk, she could only crawl about on her stomach. She was bottle-fed until June 25, when Murie gave her a ground squirrel, which she shook repeatedly, then ate. Murie kept the pup chained as she grew but allowed her to run loose every day. She permitted strangers to pet her, played with other dogs, and would come when Murie whistled. Murie named her Wags because of her avid tail wagging. Once, the alpha female visited her pup, and tried to lead her away. Wags followed to the end of her chain, where she whined and jumped, trying to follow her mother. "If the pup had been loose," Murie wrote, "it surely would have gone with the band."
In the photographs accompanying Murie's monograph, Wags appears to be a great big happy dog—one that could easily be mistaken for a Malamute. In one photo, Wags is smiling expectantly at a small girl who is holding a stick that she's about to throw. Murie noted that he knew of two other wolves who also had been removed from their dens at an early age, and who had similar, friendly dispositions.
It's not hard to see, then, how a wolf like Wags, taken from her den by humans some hundred thousand years ago, and bred with other friendly wol
ves, could have been the first proto-dog to give a gleeful wag of her tail when she saw a human—a long, furry wolf tail that would eventually evolve into a Golden Retriever's tail, a Beagle's, a Collie's, or Merle's.
When we arrived in Kelly, Merle bounded out of the truck and gave a quick look around. My silver trailer, which I used as an office, was permanently parked under a grove of cottonwood trees. Behind it, fields of sage rolled toward the snowcapped Tetons. Snuffling his nose over the porch's steps, he wagged his tail in slow appreciation: "I know who lives here: Ted." He cocked a leg and anointed the adjacent grass.
We unloaded my kayak; Benj and I exchanged a hug, and he headed home in his truck, four miles up the road. Merle jumped into my Datsun hatchback and we bumped along the dirt lane from the trailer until reaching the potholed blacktop of the one paved road that ran through Kelly. In 1950, the village was subsumed by the expansion of Grand Teton National Park and until the present day it has remained remarkably undeveloped—a half-mile square of private land between the park, the National Elk Refuge, and the Gros Ventre Wilderness. To our left was the main feature of the village, a twenty-acre field of wildflowers and sagebrush in which moose often bedded, around it a mix of old cabins, canvas-side yurts, 1960-ish tract houses, and several newer log homes. There was a covered wagon, left from the 1890s, ancient farm machinery collapsing into the sage, and several rusting cars. I could see horses in half a dozen corrals.
The ninety-odd people who lived in Kelly—ranchers, climbers, national park rangers, carpenters, nurses, auto mechanics, plumbers, retired folks, and the odd filmmaker and writer—all wanted to be here because the land was empty of development and full of weather and animals. The thirty or so dogs who lived in Kelly also enjoyed the place, I suspected, because virtually all of them lived unleashed, in houses without fences.
Merle and I crossed the Gros Ventre River and drove another mile and a half to "Upper Kelly," the crest of a long ridge where eight trophy homes lay secluded in Douglas firs and aspens. The views were grand: all of Jackson Hole, the length of the Teton Range, and Yellowstone National Park to the north. A widow who liked my writing had rented me a cozy, well-appointed cabin, the only structure on her property.
I unpacked as Merle began to explore the field around the house. Not a minute later, he came bounding in, pumping his paws up and down and panting "ha-ha-ha."
"What is it?" I asked him.
He did a circle, lifting his head up and down the way an excited horse does.
"Show me," I said, walking toward the door.
He raced ahead of me, toward the willows south of the house, and stopped over a pancake of fresh bison poop.
He looked up at me, his tail whipping back and forth.
"Bison," I said.
He looked around. Male bison, the first to leave the National Elk Refuge in the spring, often bedded near the cabin while grazing on the new grass.
"He's around here someplace."
Deep tail wag.
I wondered how much bison poop smelled like cattle poop, and if Merle were already cutting out bison calves in his mind.
Returning to the cabin, I ate dinner, and it was almost dark when I got into bed, Merle curling up on the floor next to me. In what seemed like only a few seconds, but was in reality several hours later, I felt him put his snout under my arm and lift. I opened my eyes and stared into his. His tail was beating hard. Then I heard coyotes howling, not a hundred yards from the house.
"Coyoté," I said.
He gave an excited snort in agreement, "You're damn right they're coyotés," and ran to the front door, waiting for me to open it.
At fifty-five pounds, he was already ten pounds heavier than the biggest coyote, but a pack of them could probably kill him.
"Uh-uh," I said. "There's too many of them."
He circled frantically, ran to me, blowing breath though his lips, shivering all over, and whining.
"No. Lie down."
"Ha!" he exclaimed in frustration.
I pointed a finger at the floor. "Lie down."
He stamped his feet. I put my hand on the floor. "Lie down. You're not going out. Executive decision. Lie down."
He stared at me. I stared at him. I pointed at the floor again and said in a softer tone, "Lie down, please." I put a hand on his shoulders and gently pushed. "Please lie down."
His shoulders deflated and without disguising his displeasure he lay down, his head pointed toward the window. His ears pricked and an electric spasm went through his body every time the coyotes howled. But he didn't move.
"Thank you," I said, and saw his ears flick toward me.
About an hour later, I was awakened by the crinkling of paper and the trash can in the kitchen falling over. The coyotes were now silent. Getting up and going into the next room, I found Merle, his head in the trash can. He emerged with white freezer paper in his jaws. The elk steak that I'd cooked for dinner had been wrapped in it, and I had given him some of the meat. Coffee grounds darkened his muzzle and a piece of tomato was stuck to the end of his nose. Looking up at me, he wagged his tail with great contentment.
Taking the elk wrapper from him, I said, "No, no, no." He gave me a surprised look.
Repeating "No!" and punctuating it with a downward cut of my index finger, I returned the paper to the trash and put the plastic can on the counter, out of reach. He gazed up at it longingly.
"No dumpster diving," I said. "Come on, let's get some sleep."
I went to the bedroom door. He stayed put, looking from the trash to me and giving me a hopeful wag of his tail.
Shaking my head, I said, "Nope," then, "Come," as I beckoned to him with a come-along gesture. Taking one more look at the trash, he obeyed.
Anyone who has lived with a dog has more than likely experienced a version of this scene. After all, long before there were trash compactors, there were dogs. Researchers who believe wolves domesticated themselves, rather than humans having had a hand in the process, point out that trash was the motivating factor.
Raymond Coppinger is the best-known advocate of this theory. A biologist at Hampshire College and an accomplished sled-dog racer and trainer of sheep guard dogs, Coppinger notes that the archaeological evidence suggests dogs began to look more like dogs than wolves about twelve thousand years ago, when humans began to switch from hunting and gathering to herding and farming. Both activities gave rise to permanent settlements and refuse dumps.
"The wild wolf, Canis lupus," Coppinger writes in his book Dogs: A New Understanding of Canine Origin, Behavior, and Evolution, which he co-authored with his wife, Lorna, "began to separate into populations that could make a living at the dumps and those that couldn't." Those that could, he goes on to say, had shorter flight distances. Over time, these wolves began to evolve. They lost their long canines and large strong jaws, both necessary to kill big animals. Their head and teeth became smaller—just big enough to survive on the low-quality human leftovers. In addition, their brains became smaller, adequate to the job of scavenging trash in this new niche but not to organizing and coordinating hunts for elusive and formidable prey. Because these smaller dump wolves expended less energy to survive and reproduce, they were able to outcompete their brawny cousins.
Elaborating on his theory, Coppinger cites the work of the Russian geneticist Dmitry K. Belyaev who, starting in 1959, decided to replay the evolutionary history of the domestic dog by breeding silver foxes solely on the basis of their tameability. Within thirty-five generations, Belyaev and his colleagues observed some amazing results. The foxes lost pigment in their coats and developed a star-shaped pattern on their faces, similar to some breeds of domestic dogs. They lost their upright, pricked ears—one of the distinguishing characteristics of all wild adult canids—and retained the floppy ears of their puppyhood into maturity, just as many breeds of domestic dogs do. The level of corticosteroids in their plasma also dropped dramatically, a change in hormonal chemistry that left the animals calmer. Generation by generatio
n, the foxes selected for tameability became less wary and ever more eager for human contact, whimpering to attract attention and sniffing and licking the researchers.
Coppinger concluded that the trends Belyaev had described in his forty-year-long experiment were precisely what happened in village dumps twelve thousand years ago, when wolves with shorter flight distances began to become transformed, by natural selection, into today's domestic dogs. He thought it extremely unlikely that early people would have embarked on such a long-term wolf-taming and breeding project.
They probably didn't—at least not intentionally. But by stealing wolf pups from dens and keeping the most friendly ones—pups such as Wags, Adolph Murie's McKinley wolf—they became engaged in the very sort of experiment that Belyaev conducted with silver foxes. Their initial selection may have been random, but given how fast changes took place in Belyaev's test, our ancient ancestors could have seen similar results in fairly short order. Let a friendly pup like Wags mate with an equally friendly wolf, and let their offspring mate with other friendly wolves, and within ten or so canid generations—one-half to one-third of a human lifetime back in those days—you'd have wolves on their way toward becoming dogs.
Until recently the archaeological evidence has supported both theories—that wolves domesticated themselves when we began to live in villages, and that we domesticated wolves when we were still nomadic hunter-gatherers—although the balance was slightly tipped in favor of domestication having taken place while we were hunters. A skull fragment with the proportions of a domestic dog was discovered in Yorkshire, England, and found to be ninety-five hundred years old, a date that precedes the arrival of agriculture to that part of the British Isles by thirty-five hundred years. A mandible of what is believed to be a domestic dog was also discovered in a grave in Oberkassel, Germany. The dog who owned that jaw lived fourteen thousand years ago, six thousand years before agriculture reached its home. Then, in 2002, new evidence emerged to support the theory that we domesticated wolves long ago. Two Russian researchers announced that they had carbon-14-dated a pair of adult canid skulls found in a camp of mammoth hunters in the Dneiper River Valley, west of Moscow. Both skulls had shortened snouts—the diagnostic feature of domestic dogs—and their age created a stir. They were seventeen thousand years old.