Originally published in slightly different form on October 14, 2010 at PsychologyToday.com.
Dogs are the most diverse species of animal on earth. According to zoologist Desmond Morris, there are over 1,000 breeds, each with its own specific body type and character traits.
Meanwhile, even though the latest genetic tests show that dogs evolved from wolves, there is nothing in the behavior or morphology of the domesticated dog’s wild cousins to account for the dog’s incredible physical and behavioral diversity. So where did it come from?
Up until recently it was thought that when our ancestors bred dogs for the qualities of tameness, submission, and sociability, we were also, either accidentally or intentionally, increasing their genetic tendencies toward neoteny (a form of pedomorphosis), i.e., the retention of juvenile characteristics—both physical and behavioral—into adulthood. And these pedomorphisms resulted in variegated coats, differences in morphology, and the kinds of behavioral characteristics found in juvenile wolves.
The theory of neoteny was reinforced by the famous Russian silver fox experiments done at the Institute of Cytology and Genetics in Siberia under the direction of geneticist Dmitry K. Belyaev.
Belyaev was asked by some Russian fur traders if he could create a tame silver fox that wouldn’t bite or be afraid of being handled by humans.
He succeeded. But within a few generations, the foxes began to show other neotenous traits, wagging tails, barking. And while they exhibited no fear of humans, their coats became variegated and mottled, which decreased the value of their fur to “nulyu” (Russian for zero).
In 2002 Raymond and Lorna Coppinger presented a new model for domestication, based partly on Belyaev’s work, and partly on observations of modern wolves, some of whom scavenge at human garbage dumps. Their model stated that wolves (or early dogs), were attracted to the garbage at our ancestors’ encampments. And the animals who were the boldest, i.e., most unafraid of our human ancestors, and had the least tendency to bite, were slowly welcomed into our human packs. Over time, these bold, non-biting proto-doggies, became our closest companions.
However, since the trait of “dominance” has been equated with being able to control resources, and since the boldest proto-dogs would’ve had more control over who, within in their specific family groups, were able to gain access to the human garbage, there are still two unanswered questions. How does selecting for dominance/boldness translate into the opposite, and supposedly neotenous, trait of submission? And if our ancestors were breeding for the neotenous quality of submissiveness, why do so many dogs still exhibit dominant tendencies?
There may be another problem. While the Coppingers’ “dogs-as-scavengers” theory, and Belayaev’s work with foxes are important steps in our current understanding of canine evolution, they’re still based in large part on the idea that diversity in dogs is solely (or primarily) the result of human intervention, having little to do with some inherent quality found in the dog/wolf/(fox) gene pool.
New genetic research may change that. Evolutionary biologist Ursula Goodenough wrote about this research recently for NPR. “Breeding programs,” she writes, “can only yield as much variation as is harbored in the gene pool, and the dog gene pool [is] a gold mine.”
So what’s inside this gold mine?
Two things: insertional mutations, and tandem-repeat sequences.
Goodenough: “Dog genomes harbor DNA sequences, called mobile SINEC_Cf elements, that tend to leave one chromosomal location and insert themselves into a second ... Should they happen to insert into a gene or a regulatory element, this modifies the encoded genetic information, generating ‘insertional mutations.’ It’s been estimated that dog genomes have at least 11,000 potentially mobile SINE elements whereas human genomes have less than 1,000.”
The second source of Fido’s diversity comes during fetal development. That’s because dog DNA also carries a feature called “tandem-repeat sequences,” where one bit of genetic code is repeated over and over (and over and over). “When such regions are copied in the germ line,” Goodenough says, “the copying enzymes tend to ... synthesize too many or too few repeats, generating ‘slippage mutations’ in eggs and sperm that are inherited by offspring. The slippage rate [is] far higher in dogs than in other carnivores.”
The next question is, at what point did the insertional mutations and slippage rates in the dog’s DNA come into play? Was it during the domestication process, or were they already there, lying in wait somewhere inside the wolf’s DNA?
We know that all wolves exhibit the same basic morphology, species-wide, with only fairly minor variations in size, color, coat density, etc. So on first glance it seems very unlikely that they would possess the genetic blueprint necessary for all the variations we see in domesticated dogs. Yet it turns out that the DNA of modern wolves also shows the same high levels of the two mutational factors. So apparently, dogs did, in fact, inherit their diversity and variability directly from wolves.
What does this have to do with a unified dog theory?
For the past six or seven years, key figures in the positive training movement have been dismissing or denigrating the dog’s genetic history. Dr. Ian Dunbar, a key figurehead in the movement has said, “Learning from wolves to interact with pet dogs makes about as much sense as, ‘I want to improve my parenting—let’s see how the chimps do it!’“ (This is based on a comparative DNA analysis between dogs and wolves in relation to roughly the same percentage of DNA shared by humans and chimps.)
While this idea makes sense on a certain level, there’s such a huge divide between humans and our closest genetic relatives, that there’s really no comparison to dogs and wolves. It’s true that chimps are much smarter than we previously thought, but they still don’t design and construct buildings, they don’t play guitar, write poetry, build airplanes, hold elections, take summer vacations, shop for shoes, etc.
So yes, there are differences between dogs and wolves, but it’s not as big a divide as the one that exists between humans and chimps. And the key differences exist primarily because of the dog’s relationship with humans, a relationship that for thousands of years was based, not on the dog’s talent for scavenging, but on how our ancestors used the dog’s hunting instincts, which were directly inherited from the wolf.
So while the Coppinger model of domestication may be valid, at least in part, and while neoteny is surely a factor in terms of how dogs fit in to a human household, neither model can successfully explain how dogs-as-scavengers ended up being herders, pointers, ratters, sighthounds, scenthounds, retrievers, and on and on.
Other questions remain. For instance, do foxes have these same mutational qualities in their DNA? If so, are they found in the same levels as in dogs and wolves? (My hunch is that foxes have them, just at lower levels). After all, foxes are the only canid who don’t hunt large prey by forming packs.1 And the only way the pack style of hunting can be successful is through variability in temperament, relative to each animal’s role in the hunt: some need to be bold while others need to hold back, or circle the prey, etc. That’s why in every pack, some wolves have a direct (or dominant) temperament, while others are more indirect (or submissive). If they all had the same approach to prey, the hunt would surely fail.
This diversity of temperament can also be seen in every litter of puppies, from great Danes to Chihuahuas, a clear spectrum from the most direct (or “dominant”) to the most indirect (or “submissive”). And with all the different kinds of breeding programs humans have devised over the last 14,000+ years, why does this diversity—this spectrum from dominant to submissive—still show itself with such clarity and exactitude in each and every litter of puppies born to every female dog, in every breed imaginable?
It has to be related to the prey drive. So either evolution hasn’t been paying attention to the fact that dogs no longer need to hunt large prey to survive, or else there’s something else contained within the wolf’s style of hunting that’s vital to the domesticated dog’s relationship with us. After all, homo sapiens and some members of the canidae family are the only two types of land animal with an evolutionary history of hunting large, dangerous prey by working in concert.
Most of us don’t think of ourselves or our dogs as predators. But glimmers of that early relationship still show themselves in our daily lives. Whether we’re taking the dog for a walk (the search), or tossing a Frisbee (the chase), or laughing at the way a puppy “snaps the neck” of her new toy (the kill bite), underneath it all, dogs and humans share an emotional bond that goes back 14,000 years or more.
There’s no getting around the fact that no matter how evolved we are, both species still have aggressive tendencies, emotions, and impulses. Human aggression is usually expressed through playing (or watching) sports, or else it’s sublimated into our work, or stimulated and released by certain types movies. Dogs offload their aggression into toys and games. And in order to live in harmony with others, each of us—dog and human—needs a safe means of offloading aggression.
So despite the very sensible and rational idea that we don’t need to know anything about the wolf in order to train our dogs, it seems to me that understanding where a dog’s aggressive nature comes from, and knowing how to redirect that aggressive energy into a safe outlet through play, may be one of the most important things we can do for our dogs, and for ourselves.
Next time: Understanding the Real Wolf Model.
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1) Cape hunting dogs (the domesticated dog’s most distant relative) hunt in packs, although their hunting style is based on sheer weight of numbers, which is not related to the wolf’s chase-and-ambush style, a style that coyotes (and sometimes dingoes and jackals) use when they need to hunt large prey.