Science + Technology

An evolutionary tale about dogs and humans

sleeping dog on bed

A study of the evolution of dogs has opened new and unparalleled doorways to understanding how genes and the genome produce diversity, people attending a recent symposium hosted by the UCLA Center for Society and Genetics learned.

Held Feb. 25-26, the two-day public symposium, “Made for Each Other? Dog and Human Co-evolution,” brought together geneticists, behaviorists, dog lovers and trainers, historians, cultural anthropologists, ecologists, artists and many others to discuss the genesis of dogs and explore the changing and complex relationship between dogs and humans.  

Dogs and humans have essentially evolved alongside each other, migrating together across continents. Today, there are no human populations that do not have dogs as an integral part of their culture.

All dogs — those that are considered “village” animals who still roam in packs and breed at will, as well as those that are “breed” dogs who live with humans — share a common ancestor, the wolf. But there was no single wolf-to-dog event that created the dog, according to genetic analyses and the fossil record, said Robert Wayne, UCLA professor in ecology and evolutionary biology. Rather, the emergence of the dog was an ongoing, long-term, widespread process as wolf populations interacted with humans.

“Wherever there are wolves and humans,” said Mark Derr, author of “Dog’s Best Friend,” “you end up with dogs.” While some wolves became commensal with humans, and those human-associated wolves evolved over time into dogs, the vast majority of wolves has remained wild and has continued to live in packs, hunt prey and care for their offspring as they have for millions of years.

The genomes of village dogs around the world show a very different genetic signature compared to purebred dogs, according to Adam Boyko, research associate in genetics at Stanford University. “Our research shows that, in general, village dogs are direct descendants of ancient pre-breed dogs, not a mix of various breeds.” While village dogs seem to have a stronger genetic signal of Asia as their ancestral home, breed dogs share more unique genetic traits with Middle Eastern wolf populations.

UCLA postdoctoral fellow Sharlene Santana from the Center for Society and Genetics meets Dreamer, a therapy dog with the UCLA People-Animal Connection.

From beasts of burden to shamans

As humans and dogs began to co-exist, they migrated together across the globe. In fact, in many cases, dogs may have facilitated humans’ movement into more hostile parts of the world by carrying loads, hunting, scouting and fighting off predators.

The relationship of dogs to human societies varies widely. For example, many cultures use dogs as work animals. Until a few decades ago, dogs in the United States were primarily farm animals, said Richard Cupp, professor of law at Pepperdine University. As humans became more urban, dogs became more domestic and integrated into the human family.

Laws about dogs evolved as well, Cupp said. “Whereas dogs were once considered ‘things’, and the property of the master, now dogs are seen in some states as legal inheritors in wills,” he said. And if someone kills a dog, the dog is considered to be more valuable than just property because the loss of a dog can cause extreme emotional pain and distress.

Among the Runa Indians in Ecuadorian Amazon, dogs are mainly used as hunters, said Eduardo Kohn, assistant professor of anthropology at McGill University. The Runa use a special conjugation of their language to address their dogs—a construction that is never used in human-to-human speech. If their dog misbehaves, they give it hallucinogens to turn the dog into a shaman. The Indians will talk to the dog in a special language to teach it how to behave, but they will also tie up its mouth so it can’t talk back to them, Kohn said. “They want to socialize their dogs into human norms, without allowing the dog to actually become human,” he explained.

Dogs have shown their usefulness in other situations. For example, scientists have documented evidence that forming a human-canine social bond may not only help calm and relax people during stressful situations, but dogs as well.

Karen Allen, research professor in the School of Medicine at SUNY Buffalo, described research showing that dogs can help decrease the stress response in humans who are given a difficult mental task. She also suggested that the benefits are mutual — that oxytocin increases and mutes the stress response for both dogs and humans when they are allowed to be together in social contact. Dogs also seem to buffer their humans from elevated blood pressure in reaction to stress, she found, in particular for patients using medication to decrease hypertension.

Mixing and matching

Humans have been breeding and cross-breeding dogs for millennia, with the height of this activity peaking in the 1800s in Europe. The result is more than 300 registered dog breeds exist today.

One outcome of this strict breeding, according to Heidi Parker, senior staff scientist at the National Human Genome Research Institute, has been the sharp increase in disease in purebred dogs, compared to mutts, because purebreds are homozygous (having two of the same copy of a gene instead of two different variations) for many conditions. Another outcome has been the clear segregation of alleles across breeds, making the search for genes leading to phenotype, or physical characteristics, much easier in dogs than for almost any other species.

Blaire Van Valkenburgh, professor of ecology and evolutionary biology, displays the skulls of modern dog breeds to demonstrate genetic diversity.

As one example, Parker showed how her lab group has been able to isolate one gene that is responsible for short legs in dachshunds, Scottish terriers and 17 other breeds, as well as the genes most responsible for hair variation and for overall body size in dogs.

Among the many groups and individuals participating in the symposium were Cue the Dog!, whose members showed off their dogs' skills in obedience and agility exercises; Los Angeles search dogs and their handlers; the UCLA People-Animal Connection Therapy Dogs; and local dog trainer Robert Cabral, founder of Bound Angels in Malibu. Cabral’s group specializes in rehabilitating shelter dogs that are considered ‘beyond repair’ and condemned to death.

UCLA’s Design | Media Arts Professor Victoria Vesna and her students presented a “Sniffing Booth” in collaboration with Siddharth Ramakrishnan, a research associate in electrical engineering at Columbia University. They showed how dogs perceive the world through smell, which in dogs is so refined they can detect ovarian cancer in women before it is detected through other medical techniques.

Through its annual symposia that are open to the public, the UCLA Center for Society and Genetics aims to provide multidisciplinary perspectives on contemporary issues at the intersections between biology and society. The center recently launched two new majors, in human biology and society (B.A. and B.S.) that will take the same problem-based approach to examining issues that are inextricably biological and social.

All of the lectures will soon be available online at this website.

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