Pedomorphism and behavioral development in the domestic dog

Pedomorphism is the retention of juvenile traits or characteristics until adulthood, usually caused by neoteny, the delay in the development of an animal. The animal goes through puberty to reach sexual maturity, but retains certain youthful physical and / or psychological characteristics.

If the genes that determine maturity are mutated, then the animal will mature for up to, say, a year, and that will be considered normal adult development for that line. The creation of all the breeds of dogs that we see today is due to mutations and selection of these genes.

Mutation and selection never involve just one trait, but also many others, desirable or not. The most prominent example of this can be seen in the foxes of Belyaev. In the 1950s, Dr. Belyaev, a Russian physiologist and geneticist, set out to see how long it would take him to fully domesticate a species “from scratch.” Since the beautiful dark charcoal fur of the silver fox (a melanistic version of the better known red fox) was so highly prized in Russia, Dr. Belyaev and his team had very easy access to large numbers of these animals. But docility towards humans wasn’t the only trait that distinguished these foxes from their non-domesticated counterparts. After several generations, foxes began to exhibit dog-like physical characteristics such as a curly (spitz) tail, pendant, lop-eared, smaller skull, and ‘unnatural’ coat colors and patterns such as light silver. , chocolate and peep (white with colored spots).

They also barked and whined for attention, a behavior limited to rearing wild canines, unlike our domestic dogs, which retain the ability to bark throughout their lives (a trait humans appreciated when they realized that these animals could alert them). an intruder or other danger). The foxes’ dentition also changed, as with our domestic dogs, they had the same number of teeth as their wild ancestors, but with a smaller jaw, some of the teeth (the second and third premolars) have to sit at an angle. with respect to others. Possibly the most curious trait to appear in these domesticated foxes was a second annual heat cycle, just like in dogs (with the exception of Basenji).

Given that the selection process (in both dogs and foxes) focused on docility and trainability, and certainly not aesthetics, what does coat color have to do with these traits? It turns out that the genes that code for melanin are also involved in other processes, such as the metabolism of neurotransmitters, namely adrenaline and dopamine; the former is a chemical released in response to stress, responsible for the fight or flight response, and the latter is the main neurotransmitter involved in reward-motivated behaviors. A mutation somewhere in these genes caused a decreased adrenergic response, increased sensitivity or production of dopamine, as well as an alteration in melanin production, resulting in the variegated coat patterns seen in both dogs. domestic as in foxes.

Although dogs and wolves belong to the same species, it is pedomorphism that makes dogs so tame and wolves not. In the domestic dog, the development of the limbic system is decreased, resulting in a 20% decrease in size in dogs compared to their lupine relatives. A smaller limbic system means a reduction in aggressive and fearful responses. Docility and fearlessness towards humans are traits that play an important role in the mutual success of the human-dog relationship.

Almost all of the traits that we consider desirable in our dogs are essentially juvenile wolf characteristics – being friendly, outgoing, and dependent animals is what makes dogs so easy to bond with. In a way, dogs can be considered adolescent wolves in their behavior (barking, whining, dependence on parental figures for essential resources and affection …) as well as in some physical characteristics, such as hanging or semi-erect ears and a shorter one. , wider muzzle, as seen in many breeds of dogs.

Coppinger and Coppinger were the first to attempt to group dog breeds based on their behavioral maturity with respect to wolf development, hypothesizing that certain facial features comparing adult dogs to age-specific wolf pups indicated their level. of maturity. The younger the puppy looks, the more pedomorphic it is. And although the previous statement is too simplistic, it is true that many breeds resemble (in terms of the shape of the muzzle and the bearing of the ears) a wolf cub at the same level of development maturity. For example, mountain dogs or mastiffs, such as the Rottweiler, with a relatively short, wide muzzle and hanging ears, have a profile similar to that of a two to three week old wolf pup. They are among the most playful and jovial breeds, considered “perennial pups.” Not far away, we have many retrievers, such as the Golden Retriever and the Labrador Retriever, along with many dogs, such as the Beagle. The slightly thinner muzzle and hanging ears seem to suggest the resemblance to a slightly older wolf cub; These dogs tend to have more oral fixation than other breeds and enjoy chewing and playing with objects; in fact, at three to four weeks of age is when wolf cubs begin to venture out of the den and explore. Moving further, we have the Collies, with their semi-erect ears and more graceful snouts, they look more like wolf cubs about three to four weeks old, with their strong desire to chase. Lastly, we have many Nordic breeds, shepherds, and sighthounds, all with decidedly more lupine traits: erect ears and a long, pointed snout. They are most like wolf cubs between six and ten weeks of age, with a gradually increasing prey drive.

Despite a clear correlation between appearance and maturity, the association is not perfect. There are many breeds that have traits that are not seen in wolf pups, due to the increasing popularity of selection for physical rather than temperamental traits and a predilection for hypertypes, in other words, animals that possess exaggerated physical characteristics that are not they are only useless, but typically harmful. (short and / or deviated limbs, bulging eyes, brachycephaly, etc.), the model proposed above is becoming increasingly unreliable and attempts to deduce the temperament of an individual by analyzing the allometry of the muzzle (the relationship between size and shape) and ear bearing is a guess at best.

Although our domestic dogs are far removed from their wolf relatives, certain wild behaviors of adults still persist in their ethogram, but with missing pieces or no precise ending. The most obvious example of this can be seen in sheepdogs. These animals go through all the initial stages of hunting: they stalk and chase their prey, some even bite their heels, but there is no killing or consumption of the livestock they raise. While this motor pattern is very useful for humans who work with these dogs, it is absolutely useless for the dogs themselves; it is simply self-remunerating: the reward lies in the behavior itself (herding), rather than reaching a specific end (satiating hunger).

Learning and play behaviors are youthful traits that decline as an individual ages, so it has been hypothesized that even humans are pedomorphic, retaining a heightened ability to learn beyond adolescence and well into Adulthood. And not just humans, it has been hypothesized that all domestic animals are pedomorphic versions of their wild ancestors. It is logical, then, that the selection of juvenile traits (kindness, dependence on parental figures …) would produce an individual with a greater capacity to learn even in adulthood, a trait that humans would definitely look for in working animals. with them.