| IT'S NOT OFTEN that a registered breed of dog starts with a castoff that even the pound didn't want and a stray plucked out of the woods. But it is even less likely that such animals would provide one of those rare "Eureka!" moments in science, drawing back the curtain on both evolution and human culture, and providing clues to the mysterious origins of the long, fruitful partnership that exists between humans and canines.|
And yet, that's exactly what happened with the shy enigma of a creature known as the Carolina dog, which just may be a remnant of the first animals to accompany humans across the Bering land bridge to North America thousands of years ago. Then again, it may be nothing more than a modern mutt; no one is exactly sure, and the genetic evidence, while suggestive, is thus far inconclusive. Regardless, the Carolina dog, and several other demonstrably primitive canids, some nearing extinction, are part of a controversial reexamination of how modern dogs arose, and even more fundamental questions about the process of domestication itself.
If you passed a Carolina dog on a back road in humid South Carolina Low Country, where stands of tall longleaf pine alternate with crop fields and cypress swamps, chances are you wouldn't spare it a glance — it would seem to be just a scrawny, medium-sized mongrel with a reddish-yellow coat, upright ears and a whiplash tail curling up over its back, what rural Southerners have long called a "yaller" dog. And for years, that's all I. Lehr Brisbin, Jr., thought they were, too
Brisbin — "Bris" to his colleagues at the Savannah River Ecology Lab (SREL) in Aiken, South Carolina — saw these skittish feral dogs from time to time. Brisbin is a senior ecologist on the sprawling Savannah River Site, a huge nuclear reservation carved out of the local farmland in the 1950s by the federal government, which built reactors there for the defense program. The reactors are shut down now, and the Savannah site — 310 square miles of mostly forest and wetlands — is a National Environmental Research Park. Fenced off with barbed wire and closed to the public, it is a fertile haven for wildlife despite some areas with residual radioactivity. Brisbin, a trim man in his late 50s with bottomless energy, is a polymath with professional interests that range from alligators and box turtles to wood storks and furbearers. His graduate work on the bioenergetics of reptiles and birds first led him to study red junglefowl, the ancestors of modern chickens. And that sparked a curiosity about the process of domestication in animals, which in turn meshed neatly with his lifelong passion for dogs and dog training. And that led him, eventually, to Horace and Marion.
Horace was a stray, white with brown markings, found wandering in the late '70s on the boundary of the Savannah River Site. There wasn't anything terribly special about him — he seemed just a typical rural mutt of the sort you'd find chained to back porches and doghouses from the Carolinas to Texas. Brisbin, whose specialty at the time was training American Staffordshire terriers and bloodhounds, added Horace to his kennel of show dogs, and for several years didn't spare him much more thought. Which is a little odd, because Brisbin was beginning to think about feral dogs. Early in his research on domestication, he became fascinated by the origins of truly wild dogs, like the dingo in Australia, a honey-gold dog believed to have come to the island continent with humans about 4,000 years ago. He wondered whether the dogs that came to North America with humans might have been similar to dingoes, and he studied the archaeological and anthropological evidence. And he spent his spare time learning about the so-called pariah dogs of the Old World, which share traits with dingoes. In many corners of Europe, Asia and Africa, on the margins of human civilization, there are dogs lurking in the shadows — not pampered house pets, but untamed, often malnourished animals scavenging for scraps and garbage, avoiding people, surviving on the edge between wild and tame. Regardless of the setting — Afghanistan, Korea, Malaysia, the Papua New Guinea highlands — they frequently share common attributes: shorthaired coats that may be multi-colored but are often ginger, curled tails, erect ears and foxlike faces. In India these animals are called pariahs, after the low-ranking social caste, and that name has come to be applied to such populations elsewhere. In fact, Brisbin has defined a "pariah niche," a pervasive canine lifestyle that revolves around scavenging garbage near human settlements.
One winter day several years after Horace arrived, Brisbin had him out for a run with his other, pedigreed dogs. That day, for some reason, Brisbin looked beyond Horace's piebald coat to his shape and proportions, and it struck him that the dog looked just like a dingo, like the pariahs halfway around the world. "At that moment everything just fell into place," he says now, 20 years later. Brisbin realized that he'd been seeing dogs that looked like dingoes for years, roaming the woods of the Savannah River Site, often turning up in the traps he'd set as part of his regular furbearer surveys. On a hunch, he drove that day to an animal shelter just to see if they had more of these dingo-like dogs. Sitting in a kennel, with only her head poking out of a box, was a dog that looked like she had stepped out of the Australian outback.
The shelter operators thought Brisbin was crazy for taking the untamed animal, but they were also glad to find a home for such a thoroughly unadoptable dog. "So they go into the doghouse with a noose pole and drag her out screaming, spread-eagled, leaving claw marks through the kennel, and put her, urinating all over herself, into this cage in the back of my car. And I was handed a card, which I have to this day." Bris shakes his head and laughs. "It's got this little dog face, and it says, 'We are pleased you found room in your heart and your home to adopt this "Little One"' — who was yelping in my cage, shaking like a leaf — 'who comes fully guaranteed to love, protect and be loyal to you as long as it lives.' "
"And you know, ironically, she has", he says. Brisbin named the dog Marion, after Gen. Francis Marion, the "Swamp Fox" of the Revolutionary War. And while she has never become his "little one," she did learn to accept and tolerate him, the same way an aloof cat tolerates its owner, respectful but always distant, preserving her space and dignity. Today, Marion is a 14-year-old matriarch, her coat somewhat threadbare, her muzzle gray and her eyes cloudy, her gait stiff and arthritic. But she retains some of the wildness that marked her early life; even around Brisbin she is shy and at a remove. A visitor who sits for a long time, pretending that he has no interest in her, may receive a careful sniff at his knee — but if he reaches to stroke her scarred muzzle she pulls back, not in alarm but maintaining distance.
Brisbin acquired more of these feral pariahs, which he'd taken to calling Carolina dogs, from shelters and from the wild in South Carolina and Georgia. A number of them came from land surrounding large federal reservations, like Fort Gordon near Augusta, where much of the terrain remains undeveloped and undisturbed. Brisbin kept his Carolinas in a complex of kennels in an 18-acre enclosure where they could roam in the woodlots and fields. They started producing puppies — and surprises. Regardless of their origin, the Carolinas did things never before observed in domestic dogs. They had peculiar breeding cycles, starting with a rapid-fire, thrice-annual estrus in young females (perhaps a way to ensure quick breeding before diseases like heartworm took their toll) that later settled into seasonal reproductive cycles peaking in spring and late summer — the period, Brisbin notes, when small mammals are most abundant. Some pregnant females dug elaborate underground dens in which to give birth, unlike most domestic dogs, which usually just crawl under a porch or into a handy pile of brush. When she was in estrus or after her puppies were born, a captive female would carefully cover her excrement by scraping sand over it with her nose. To Brisbin's bafflement, the animals also dug what he calls "snout pits," hundreds of small, conical depressions in the dirt that exactly fit the dogs' muzzles. Most snout pits are dug by females, between September and January. The dogs seem to be eating something, "but when I pull them out and look, there's never anything there," Brisbin says. They are particular about where they dig, and Brisbin can only conclude they're eating the soil itself, perhaps for its minerals. With time, Bris became convinced he had stumbled onto something unique. The size, shape, color and behavior of the Carolina dogs, so similar to the the traits of other primitive canids, suggested they might be a relic of the first dogs to enter the region. He compared their skulls with those of Indian dogs from 2,000-year-old archaeological digs at Savannah River; they were similar, but there was too much individual variation among the fossils to be certain.
But the fact that Carolina dogs are most often found in wild, swampy, sparsely settled regions, instead of more heavily populated areas where stray dogs are most common, is a strong indication to Brisbin that these are more than just mongrels. Others agree; Bris has convinced both the American Rare Breeds Association and the United Kennel Club to recognize the Carolina dog. As with any registered breed, there is now a Carolina dog studbook to document and control breeding, and Brisbin's animals have even started winning "best in show" at multiple-breed dog shows.
They are, of course, individuals. There are Lucy and Cici, both captured as wild pups, who vanish down their den holes before a stranger even steps from Brisbin's car. Dibble, the dominant female of the pack, is a bit standoffish, but Bo Pup, an adolescent, is all over me in seconds with open-mouthed greetings. Surrey is a medium-sized female, daughter of Horace and Marion; Morgan is a solid, friendly chap whose drop ears belie his Carolina dog genes.
If Marion is emblematic of a pariah dog's ancestral shyness, Taz is the polar opposite: a Carolina dog deeply, passionately, enthusiastically in love with people. He's Brisbin's home dog, a white-and-tan whose parents were both taken from the wild. Bris is bringing him up through the ranks of obedience training, aiming for the highest level. On the lead, Taz reacts instantly to hand and voice signals, but when the leash comes off as we walk in the woods, he vaults up steep banks with ease, and scrambles out on fallen tree trunks that span 20-foot-deep gullies. On an oppressive June evening, with the temperature still above 100 degrees Fahrenheit and the sun a fierce red ball in the western sky, I walk with Bris and a dozen or so Carolinas across Banbury Cross Farm, near Aiken. The dogs lope easily ahead of us, the low sun backlighting them, creating little moving nimbi of gold. Billy Morgan Benton, a big, outgoing man with dark hair slicked back wet under his cap, whistles to his pack, he and farm owner Jane Gunnell breed the dogs here, working with Brisbin to establish the Carolina dog as a domestic pet. They are frolicsome, friendly animals, Gunnell says, but out in the wooded nooks and weedy fields of the farm, their primitive traits become obvious. The dogs are ginger, a red-brown that fades to pale buff on the flanks and belly, the same color as fallen pine needles and dead grass. They fan out through a low scrubby field, moving into the damp breeze, zigzagging and coursing with their noses low and their curved tails at half-staff. Suddenly one dog makes a sidestep, its supple neck arching; the tail snapping high, the longer, whiter hairs along its underside flaring, reminding me of a deer.
The effect on the rest of the pack is electric. Within seconds, all the dogs converge on the spot, tails moving like semaphore flags. One plunges its head into the grass with the speed of a heron's stab, but it misses. Something small skitters through the weeds, and another dog leaps, coming down with mouth and front feet together, a predatory exclamation mark — Bam! There is a tiny squeak, and the mouse vanishes in one gulp.
"I would suggest that you're watching a reenactment of a dog pack out hunting 8,000 years ago," Brisbin says. While he doesn't claim that Carolina dogs are direct, genetically pure descendants of the original dogs that crossed the land bridge, he believes that they re-create their look and behavior.
"The Carolina dog is a hypothesis, he says. "A hypothesis that there still exists in certain parts of the United States, most likely in relatively uninhabited broad expanses of natural habitat within the Southeast, remnant groups of dogs whose morphological, behavioral, ecological and genetic traits may approximate those of the first dogs to enter North America.
"It's all part of the package. Morphology and behavior go hand in hand," Brisbin says, gesturing to the lean shape of a nearby dog snuffling through the underbrush. That sinuous, blue-heron neck doesn't seem relevant without the pointed muzzle for stabbing at prey, and the upright ears for sharp hearing, and the long tail with its pale underside for signaling to the rest of the pack. Whether the Carolina dog is an ancient holdover or a modern throwback, its shape and behavior make a lot of evolutionary sense. Genetics may tease out the origins of the Carolina dog, but so far the results are mixed. Recently, Brisbin and his colleague Travis Glenn, a molecular geneticist at SREL, have been looking at the mitochondrial DNA (mtDNA) of Carolina dogs — the genetic material passed down through the maternal line, and a potent gauge of relationships among animals.
When the mtDNA from Carolina dogs, dingoes, singing dogs and a variety of domestic breeds are compared, a phylogenetic tree — a sort of family tree showing their relationships — can be made. In this tree, the Carolina dogs tended to clump together near the base, an intriguing though tentative result that suggests the Carolina dogs may possess primitive genetic traits.
"Most of the dogs coming out at the base of the tree are Carolina dogs or dingoes," Glenn says. "If there were no basis to the argument that Carolinas are primitive, they'd be all over the tree, but they're grouped together." Glenn, who had initially assumed the Carolinas were just domestic dogs, admits he was stunned when he saw the results. "I had to go out for a beer." Brisbin is cautious in interpreting the results, especially since the mtDNA sequences of some domestic dogs also grouped with the Carolinas at the base of the tree. "It's interesting that at a preliminary stage, most all of the Carolina dogs turned out to be primitive" — but so did boxers, German shepherds and Labrador retrievers, among others. It will take more research to sort out exactly what secrets are hiding in the "yaller" dog's genes.
The Carolinas are part of what Brisbin calls "the great arc of the red dog," the worldwide distribution of pariah canids. From their probable point of evolution somewhere in Southwest Asia or the Middle East, the ancestors of today's domestic dogs spread out in tandem with humans into Africa; and southeast through Java, Australia, New Guinea and then island-hopping through the South Pacific in rafts and canoes; north through Korea, Japan, Siberia and then into North and South America.
In remote corners of the world, away from the later waves of European dogs that hybridized local varieties out of existence, some of the original dogs still survive. Unlike the Carolinas, their ancient lineage is undisputed. The most intriguing, and perhaps the most primitive, is the NewGuinea singing dog. Low-slung and muscular, weighing about 25 pounds, with short legs, a long torso and a wide face, it is a curiously feline dog with an ability to climb and jump that is unmatched by any other breed — a handy trait in the sodden, jumbled forests of the New Guinea mountains, where it can scramble up trees like a cat. The name comes from its weird, harmonic howls, whose unearthly qualities prompted one of the highland tribes to claim the Creator had replaced the dog's tongue with the quill of a cassowary, a native bird. These dogs are truly wild animals and rarely seen.
Although singing dogs have been in New Guinea for at least 4,000 years, living examples were only discovered by the outside world in the 1950s. At that time, they were classified as a separate species of wild canid, although today they are officially grouped with the domestic dog. Unfortunately, purebred singers have all but vanished from New Guinea as European dogs have moved into the highlands. Today only about a hundred exist in captivity, the descendants of a handful of wild-caught animals, and most of those have been neutered or are too old to breed. Brisbin has a couple of pairs and has been working closely with Janice Koler-Matznick of Central Point, Oregon, an expert on singers who has founded the Primitive and Aboriginal Dog Society to promote the conservation of ancient canids. As the singing dog adapted to the rigors of life in the wet forests of New Guinea, so did dogs elsewhere evolve to fit the local climate and conditions- both through natural selection and selective breeding by humans. There may have been hybridizing with wolves, coyotes and other wild canids, further stirring the genetic pot. Based on skeletal remains found at ancient village sites, it appears there were recognizably different types of domestic dogs thousands of years ago, from tiny toy-size breeds to animals with the heft of modern mastiffs. While bones tell part of the story, they say little about a dog's outward appearance. Fortunately, in the case of early dogs in the Americas, pre-Columbian art, the accounts of early explorers and works of frontier artists fill in some of the blanks. The average Indian dog apparently looked like a dingo — with a fairly short coat, upcurved tail and upright ears. Judging from 19th-century paintings, the Iroquois raised dogs that would look at home in Brisbin's pack of Carolinas.
Along the Northwest coast around Vancouver Island and the Olympic Peninsula, the Makah and Coast Salish tribes kept two breeds, both now extinct — a typical, dingo-like village dog, and a smaller, longhaired variety with a tightly curled tail raised exclusively for its fur, which was woven into blankets. Dogs in the Arctic, sub-arctic and Great Plains, on the other hand, resembled wolves, with large frames, heavy coats and shaggy tails. Many explorers said they could scarcely tell the difference between a wolf and a Plains dog, which was well-known for its ability to drag heavy loads for humans. "There's no doubt that the dog is closest to the wolf," says Juliet Clutton-Brock of the Natural History Museum of London, and one of the world's foremost authorities on the prehistory of domestic animals. Studies since the 1950s reveal many similarities between wolf and dog morphology and behavior, and experts have formed a consensus: the more than 400 breeds of domestic dog, from Chihuahuas to Saint Bernards, were descended from one of the small, southern Asian subspecies of the gray wolf — perhaps the Arabian wolf, or the Indian wolf immortalized by Rudyard Kipling.
The oldest fossils of what are undisputedly dogs date from about 11,000 or 12,000 years ago in Southwest Asia, making dogs the oldest of all domesticated animals. Archaeozoologists — scientists who study the remains of animals in association with humans — assumed that the domestication process would have started much earlier, perhaps 15,000 years ago, in conjunction with the rise of permanent villages and the advent of agriculture.
But in 1997, a team led by evolutionary biologists from the University of California at Los Angeles dropped a bombshell. After analyzing DNA from wolves and wild canids around the world, as well as from nearly 70 breeds of dogs, they concluded that dogs and wolves probably split off from each other originally more than 100,000 years ago — almost the same time that anatomically modern humans were first emerging, and long before anyone suspected domestication was possible. While hailed by some molecular biologists, the UCLA findings have been questioned by paleontologists and archaeozoologists. Last August, at a symposium on the history of the domestic dog at the University of Victoria in British Columbia, sponsored by the International Council for Archaeozoology, the controversy was a major topic. One explanation that might reconcile the archaeological record and the DNA findings is that the dog's ancestors were wolves that split off from other wolf lineages 100,000 years ago, even though dogs themselves didn't evolve until more recently.
While debate swirls around the timing of dog domestication, some experts are taking aim at the fundamental notion that dogs and other animals were domesticated through a human-directed process. "The standard explanation of how domestication began — that people brought in young wild animals, which they tamed and bred over many years to produce domestic stock — is a myth," argues archaeozoologist Susan Crockford, an expert on the Northwest wool dog, and the organizer of the Victoria symposium.
For quite a while, biologists have believed that domestication took place over a long time: a period that would cover taming an animal, molding it from a wild form into a physically and behaviorally different creature. That transition period should provide lots of intermediate forms in the archaeological record — only it doesn't. Instead, the bones of dogs suddenly pop up in archaeological sites about 12,000 years ago, at the same time humans were abandoning their hunter-gatherer culture. Whether you're talking about dogs, sheep, cows, goats, pigs or water buffalo, there are consistent differences between the wild and domesticated forms. Compared with their wild cousins, most domestic mammals tend to be smaller, have shorter snouts, smaller brains and are more likely to be piebald or solid in color; they are more docile, reproduce at a younger age, have larger litters and have reproductive schedules, such as multiple breeding seasons in a single year, that differ from those of wild animals. Such changes also occur in domestic birds.
Interestingly, all these differences are a consequence of changes in developmental rates, especially while the animal is young, which result in a sexually mature adult with the size and some of the characteristics of a juvenile of its ancestor — a condition known as paedomorphosis. And those developmental rates, in turn, all appear to be controlled directly or indirectly by a single biochemical: thyroxine, a hormone produced by the thyroid gland, which in turn regulates a suite of crucial growth and developmental genes. Thyroxine, Crockford believes, was the key to domestication changes.
Crockford theorizes that in a sense, wild canids domesticated themselves. By creating a new environment, one in which food supplies were available to those wolves able to tolerate the presence of people, humans set the stage for rapid evolution. Fear is controlled, in part, by the adrenal gland, and adrenaline production, in turn, is one of the many biological functions controlled by thyroxine. In Crockford's view, the less fearful wolves would thrive near settlements, scavenging garbage middens and filching meat from drying racks, breeding among themselves and reinforcing those attributes. Natural selection would favor canids with thyroxine levels that produce lower adrenal response. Any pups born with a more fearful nature would simply drift away from the villages, back into the wilderness. After just a few generations, she believes, the wolves living near humans would exhibit reproductive, physical and behavioral differences, triggered by their new thyroxine patterns, that would set them apart from their wilder counterparts. They would have become primitive dogs. Only much later, long after primitive dogs had become genetically distinct and reproductively isolated from wolves, did humans begin exerting artificial selection to create distinct breeds. Crockford cites intriguing evidence for her hypothesis. For 20 years starting in the 1950s, researchers in Siberia, trying to create a strain of silver fox that would be easier for fur-farm workers to manage, began selecting breeding pairs strictly on the basis of how calmly they behaved around people. Unintentionally, the Soviets were selecting foxes based at least in part on their thyroxine levels, Crockford contends. Within just 20 generations, foxes in the fearless strain had become markedly smaller, had undergone changes in their reproductive schedule, and had developed floppy cars, curled tails and piebald coats — precisely the traits that often separate dogs and wolves, and all of which are under the control of thyroxine. "It may have taken only about 40 years, at two years per generation, for wolves to evolve into early dogs — perhaps more than that, but we can now look at that number as some sort of minimum. And 40 years is almost certainly too fast to pick up intermediate stages in the archaeological record", Crockford argues.
While some scientists look toward the dog's past, others are casting a worried eye toward the future of primitive breeds. Brisbin thinks the Carolina dog is relatively secure, although the expansion of coyotes into the Southeast may be causing a reduction in their numbers. But others, like the Tengger dog in Java and the Falkland Islands "wolf,"' are extinct, and more are threatened. Conservation organizations, already overburdened and overextended, rarely pay attention to domestic animals — even though many breeds represent important genetic diversity, and an irreplaceable slice of human and natural history.
Which brings us back to the Carolina dogs. Are they, as some people claim, a direct link to the aboriginal past, or a recent construct of the canine melting pot?
Brisbin will keep working toward a major genetic study of the dogs. He also hopes to track wild Carolinas by fitting them with radio collars, to learn more about their habits, territory and prey. But even if further research proves the Carolina is of modern origin, it still has much to tell us about natural selection and how, in a relatively short time, stray dogs were molded into an animal well suited to the wet, hot coastal plain of the Southeast. And that lesson alone, Brisbin and other researchers believe, makes this shy, lovely animal worthy of study and conservation.