Evolution of Dogs

Background

The dog (Canis familiaris) is a tame form of the Gray Wolf from which it evolved tens of thousands of years ago. The Gray Wolf is a part of the Canidae family of the order Carnivora. It is generally accepted that the dog is man’s oldest friend, a friendship that began nearly 15,000 years ago. The practice of taming the dog began tens of thousands of years ago in East Asia when early man began taming wolves.

Early people shared similar territories and hunted the same prey as the wolves and this led to several confrontations as well as social contacts that enabled a mutual friendship between man and wolf, hence the domestication of the latter. The domestication of an animal produces numerous genetic changes enthused by necessity and environmental requirements. Archeologists generally believe that wolves supplied man with food, fur, pulling loads, and protection. The genetic evolution of dogs was further stimulated by the cross-breeding of diverse breeds of wolves (PBS, para. 5).

Over the 15,000 years, that dog has been tamed, it has produced only a few landraces- groups of identical animals whose morphology and behavior have been altered by environmental elements. Through selective breeding by man, the dog has evolved into numerous breeds, and it shows more behavioral and morphological differences than any other terrain mammal. For example, the Chihuahua measures only a few inches in height while the Irish Greyhound grows to approximately two and a half feet; color differs from white through the shades of gray and brown, to black; coats vary in length, and texture varies from coarse-haired to very fine-haired, straight, curly, or soft (Derr, pp. 38).

The Earliest Evolution Path

The earliest traceable carnivorous animals evolved during the late Cretaceous period approximately 75 million years ago (the most probable animal is the Cimolestes, a small tree-dwelling animal). However, scientists today trace all carnivorous animals to the Miacis, a big animal that lived nearly 55 million years ago. Miacis was not a very ferocious animal, dwelt on trees, and fed on insects, bird eggs, and small animals.

Modern-day dogs developed from an ancestry of carnivorous animals known as ‘canids’, named after the distinctive shape of their teeth. However, before (and along with) the canids, there were various families of ferocious animals such as the amphicyonids (the “bear dogs” symbolized by Amphicyon, which appears to have been closer to bears than dogs), prehistoric hyenas (Icitherium was the first member of this group to live on the ground, rather than adopt the arboreal nature of its ancestors), and the ‘marsupial dogs’ that were dominantly found in S. America and Australia. Although they resemble dogs in appearance and behavior, these animals were not direct ancestors of modern dogs.

Other likely descendants of the dog that appeared during this epoch were the mesonychids and creodonts. The most famous of the mesonychids were the bulky Andrewsarchus, the largest terrain-dwelling carnivorous animal that ever lived on earth, and Mesonyx. Mesonyx was smaller as compared to the Andrewsarchus but bore a closer resemblance to the wolf, strangely enough, mesonychids’ descendants were prehistoric whales, rather than dogs. The creodonts, in contrast, have no living descendants. The most notable members of this breed were the Hyaenodon and the Sarkastodon, the former resembled a wolf and the latter a bear.

Early Canids

The late Eocene Hesperocyon (also known as the ’western dog’) was a direct ancestor to all canids and consequently belonged to the genus Canis. Hesperocyon was about the size of a small fox, however, its inner ear formation was similar to those of later dogs, and paleontologists have found some proof that they lived in groups and were either arboreal or lived in underground tunnels.

The second group of prehistoric canids was the borophagines, or ‘bone-crushing dogs’, armed with strong jaws and teeth adapted for tearing into the flesh of carcasses. The largest, most fierce borophagines were the Borophagus, which weighed close to 100 pounds, and the larger Epicyon. Other genera included the Tomarctus and the Aelurodon, which were average in size. It is thought that these bone-crushing dogs also hunted in packs, similar to today’s hyenas (Perlson, pp. 19).

The First True Dogs – Leptocyon, Eucyon, and the Dire Wolf

This is the point that paleontologists find a bit confusing. Shortly after the emergence of Hesperocyon 40 million years ago, Leptocyon also appeared, the two animals were not closely related. Leptocyon was the first actual canine (i.e. it was a member of the Canidae family), however, it was much smaller than Hesperocyon. The immediate descendant of Leptocyon, Eucyon, lived during the period when Eurasia and S. America could be reached from North America through either the Baring Strait or Central America. Approximately 5 million years ago, Eucyon evolved into the earliest family of the modern dog. It later spread from North America into other continents.

The story does not end there. Although canines continued to habit North America during the Pliocene period, the first large-sized wolves evolved in a different place and re-entered North America through the Baring Strait just before the Pleistocene. The most notable of these super-sized wolves is the Dire Wolf that evolved from the ancient wolf that had inhabited both North and South America.

The end of the Pleistocene era saw the rise of humankind around the world. Records indicate that the first domestication of the Gray Wolf took place somewhere between 30,000 and 15,000 years ago and this led to further evolutions that gave rise to the modern-day dog.

Theories for the Evolution of the Dog

Scientists have used Darwin’s theory of natural selection to explain why some wolves evolved to dogs while some did not. The theory is that by choosing individual foxes that are sociable and less wary of man, some features of the developmental course are influenced. Gene accumulation occurs and the offspring becomes tamer and tamer. To confirm this theory, Russian scientist Dmitri Belyaev experimented with wolves on his farm in the 1950s.

He selected foxes that were more receptive to humans and bred them. After a few generations of breeding, he noticed that the offspring developed strange features such as dissimilar fur colors, droopy ears, and curly tails. Belyaev also observed that the latter generations achieved sexual maturity earlier than their ancestors and barked more frequently. He succeeded in coming up with breeds with dog qualities. This experiment could perhaps explain how the dog evolved from the wolf, and why some wolves did not evolve. The process of adopting puppies with desirable qualities (artificial selection) and breeding them gradually led to different breeds of dogs.

Reasons for Domestication

Archeologists, paleontologists, and animal scientists have posited several theories that give reasons why man opted to domesticate wolves. According to them, thousands of years ago, ferocious wolves that were a risk to the early human communities were killed. However, their cubs were kept alive and raised within the community. As expected, the cubs grew up to be tamer and less ferocious than their parents.

Man tamed numerous varieties of wolves and bred them, leading to several different breeds. This is the major reason for the domestication of wolves and their subsequent evolution into modern dogs. Scientists concur that due to a large number of tamed cubs, the untamed population of wolves was eclipsed. In addition, due to the extensive cross-breeding among various wolf species, genetic evolution occurred among many species and led to the modern dog.

Scientists have forwarded another reason for the domestication of wolves. It has been said that being scavengers, wolves were drawn by food remains and bones at human residential areas or campsites, as such, they would often visit early man’s habitat, or follow him through the migration routes. Coupled by their friendlier and social nature, wolves easily interacted with the early man and this led to their domestication.

Proof to both of these theories is found at prehistoric campsites as well as empirical studies of modern culture. It is known that the dogs kept by the Native American tribes for transportation were direct offspring of wolves. Besides, many societies consume dog meat and this is evidence that wolves were once kept for meat, similar to cows. The practice is common in East Asian countries such as Korea, China, and Vietnam. Ironically, this is the region where dogs first evolved from wolves before moving into other areas of the world (Savolainen et al, pp. 1610).

As a result of its domestication, man and wolf had a mutual relationship. For example with each party getting benefits, wolves would have improved the sanitation by cleaning up food remains. Besides, they may have provided warmth, and they would have warned men of the presence of an intruder or stranger within their campsites or residential areas due to their sharp senses. Scientists posit that the most significant gain that man derived by taming wolves was the use of their sharp senses to aid in hunting.

A 2004 study of hunter groups with and without a dog offered conclusive proof to the hypothesis that the advantages of cooperative hunting were a vital factor in the taming of the wolf (Ruusila & Pesonen, pp. 548). This cohabitation was extremely important as it increased the likelihood of survival for early man, and the taming of wolves may have been one of the contributing factors that led to man’s success.

Some scientists, however, argue that dogs evolved while living as man’s neighbor, rather than his companion as stated in several theories. The theory states that wolves would never have had the right ‘personality’ to cohabit with early man, but was brave enough to live off the food remains discarded by the early man. The wolves were confident enough to live closer to humans, and in this manner, they evolved to get closer to their neighbors. The wolves that were afraid of man, however, grew up in another location away from the man. These wolves have retained their traits to this day and continue to live in the wild (Coppinger & Coppinger, pp. 1541).

Evidence that Links Dogs to Wolves

Many skeptics have often doubted the fact that dogs evolved from wolves, however, the evidence indicated below is enough proof of the evolutionary process.

Charles Vila has carried out one of the most extensive studies to date, which indicates that there is no justifiable evidence to prove that any other species of animal evolved to give the dog except the dog’s cousins. Vila examined several samples from unique wolf breeds, and then compared the samples with others drawn from several dog breeds. The findings from this experiment indicated that all dog breeds evolved from different wolves in different regions at different periods. The findings also gave reason for the existence of several dog breeds.

The major challenge with the study of the evolution of the dog comes from the fact that DNA evidence for this evolution does not correspond to normal codes of the molecular framework. The oldest fossils that can be linked directly to dogs date back nearly 14,000 years ago. With the intensity of evolution that has occurred from the wolf until the modern dog emerged, most scientists estimate that it would take close to 100,000 years. This shows that, unlike other species, the dog evolved at an unusually fast rate.

Another reason that supports the evolution arises from the mode of feeding. Many wild wolves fed on food remains and bones at campsites. Dogs, just as wolves, like gnawing on bones and have a habit of looking for leftover foods as soon as people leave an eating venue. Besides, both the dogs and wolves are known to wag their tails, however, wolves do not wag their tails as frequently as their descendants. These facts point to the connection between dogs and wolves and indicate a clear link between the two.

Effects of the Evolutionary Changes

Despite evolving from dogs, the difference between wolves and dogs widened during the evolutionary process and the two species can be easily distinguished today. Due to continued domestication, the differences have continued to become more apparent. The modern domestic dog has evolved into a more meek and friendly animal than its cousin descendants. Lindsay mentions “…dogs have lost the lupine carnivorous drive and predatory behavior exhibited by wild canids” (Lindsay, vol. 1). Even though dogs have traditionally been carnivorous, their diet has expanded to include a host of other foodstuffs that their ancestors did not eat.

The first variation between wolves and dogs stems from the physical attributes, mainly size: a dog is normally smaller than its ancestors. This extends to the features of the head such as the brain and teeth. A logical explanation for this observation is that dogs have lower energy requirements than wolves. Another difference is that certain dog varieties have droopy or ‘limped’ ears while wolves’ ears are normally erect. Scientists attribute the limpness to weakened jaw muscles (Coppinger & Coppinger, pp. 197). The skin of dogs is normally thicker than that of wolves, and their tails can curl upwards, an action that wolves cannot perform (Lopez, pp. 320).

Evolution has made dogs less smart as compared to their ancestors as can be seen from their daily activities. Wild dogs demonstrate little of the intricate social structure that is present among wolves, for instance, unlike wolves, the head of a pack of wild dogs does not force the other members to wait for their turn on a meal when the animals are having a group meal. Each member is free to eat and there is no eating order whatsoever.

Besides, a group of wild dogs rarely hunts together, rather, each member looks for his food and therefore acts as a competitor to the others. Wild dogs are mainly scavengers and have little effect on the wildlife ecosystem. However, wild dogs have been reported to be well-organized hunters than other animals in the Galapagos Islands, while roaming dogs show predatory activity at other animals in the wilds (Serpell, pp. 267).

Previous studies have indicated that domestic dogs can never be monogamous, however, recent findings indicate that this is false. Furthermore, mating between domestic does not have to be between a female and a dominant member of the pack. Male dogs have a strange behavior when it comes to bringing up their puppies, i.e. they do not play any role at all, and unlike the wolf family, the male dog does not kill puppies of other dogs to enhance its reproductive likelihood. Wolves are known to kill the puppies belonging to other females to increase the likelihood of survival of their pups. Dogs mature physically and sexually at a lower age than the wolves, i.e. while dogs take approximately eight months to mature, wolves will take another 14 or more months to achieve an identical level of maturity.

Not all male dogs fail to regurgitate food for their young ones a few breeds of domestic dogs regurgitate foods for their young ones and even participate in their upbringing (Pal, pp. 35).

Another difference between dogs and wolves stems from trainability. Dogs show a greater response to training than wolves. Besides, dogs are more responsive to coercive methods that employ fear, stimuli, and force than wolves (Wolf Park, para. 1).

A distinct difference is the dog’s ability to create an alert by barking or howling and to mark boundaries using its urine. Wolves also perform these acts, but less regularly. However, it is essential to note that not all breeds of a dog bark. The practice of barking is a socially acquired norm. The dog’s frequent desire to scent marks using its urine is a major trait that separates them from wolves. This action may serve as a way to communicate with other dogs, but the reason is unknown. Some scientists have speculated that it may serve as a territory marking technique, Lindsay, however, states: “canine scent-marking does not serve a territorial function, but rather functions more or less to communicate that the dog has been recently in the area” (Lindsay, Vol. 1).

Works Cited

Coppinger, Raymond, and Coppinger, Lorna. Dogs: A New Understanding of Canine Origin, Behavior, and Evolution. Chicago: University of Chicago Press, 2002.

Coppinger, Raymond, and Coppinger, Lorna. Dogs: a Startling New Understanding of Canine Origin, Behavior, and Evolution. New York: Scribner, 2001.

Derr, Mark. A dog’s history of America. San Francisco: North Point Press, 2004.

Lindsay, Steven R. Handbook of applied dog behavior and training. Iowa: Iowa SP, 2000. Vol. 1.

Lopez, Barry. Of Wolves and Men. New York: Scribner Classics, 1978.

Pal, Sankar K. Parental care in free-ranging dogs, Canis familiaris. Applied Animal Behaviour Science 90 (1), 2005. 31– 47.

PBS. Evolution of the dog2001. Web.

Perlson, Joseph. The Dog: An Historical, Psychological and Personality Study. New York: Vantage Press, 1968.

Ruusila, Vesa, and Pesonen, Mauri. Interspecific cooperation in human (Homo sapiens) hunting: the benefits of a barking dog (Canis familiaris). Annales Zoologici Fennici 41 (4), 2004. 545–549.

Savolainen, Peter, Ya-ping Zhang, Jing Luo, Lundeberg, Joakim, and Leitner, Thomas. Genetic Evidence for an East Asian Origin of Domestic Dogs. Science, Vol. 298 (5598), 2002. 1610–3.

Serpell, James. The Domestic Dog; its evolution, behavior, and interactions with people. Cambridge: Cambridge University Press, 1995.

Wolf Park. Example #1: Training Orca to sit down. 2000. Web.