by John Moffett
Are dogs just funny looking wolves? Substantial scientific evidence indicates that modern domestic dogs were originally derived from wild wolf populations over 30,000 years ago, probably somewhere in Eurasia. Dogs can interbreed with wolves to produce "wolfdogs", indicating that they have not changed sufficiently to have lost the capacity to produce hybrids. Dogs share many similarities with wolves, but there are also many differences. Dogs have smaller teeth relative to their skull size than wolves, especially their canine teeth, and dogs have smaller jaw muscles making them less capable of hunting and eating whole animal carcasses. Indeed, there is a growing list of substantial differences between dogs and wolves, especially behavioral differences, which make the case for dogs as having moved far beyond being funny looking wolves. New research is also pointing to significant differences in dog genetics and metabolism that indicate they are now quite different from their wolf cousins.
Among the many behavioral differences, most dogs bark extensively to alert other dogs and their human companions, whereas wolves do not generally bark and prefer the silent approach in most circumstances. Dogs also interact very specifically with humans, including being highly attuned to human language, human facial expressions and human hand movements. Even wolves reared entirely by humans do not show anywhere near the same degree of attunement to human behavioral queues. Clearly dogs have been bred to pay lots of attention to humans, and what the humans are doing and want to do, whereas wolves do not pay hardly any attention to human activities, except to avoid humans whenever possible. Interestingly, wolves only breed once per year in the spring, whereas female dogs typically come into heat twice per year. Dogs also typically have much larger litters than wolves. Finally, many dogs exhibit traits of "neoteny" which refers to the retention of normally juvenile characteristics into adulthood, including reduced snout size, and playful behavior.
The behavioral studies on dogs and wolves are revealing, but much of the newer information on how dogs are very different from wolves comes from modern genetics. The study of genetics has progressed extremely rapidly in the last several decades, and among many other discoveries this has led to a large and growing body of evidence that indicates dogs are not wolves in much the same way that wolves are not coyotes. Wolves and coyotes can interbreed just as wolves and dogs can interbreed, despite the obvious differences. Dogs can also interbreed with coyotes, dingoes and some jackals. So if the capacity to interbreed is used to say that dogs are just like wolves, then dogs are also just like coyotes, dingoes and jackals. The capacity to interbreed is not a good criterion for determining if dogs and wolves are just minor variations on a theme.
Nowhere, perhaps, has the debate over dog-wolf similarities been more contentious than the kerfuffle over the optimal diet for dogs. A very common claim is that dogs are carnivores rather than omnivores, but recent genetic evidence undermines that claim. There are at least 4 basic ideological camps in the dog diet controversy. The most prevalent opinion is that commercial dog kibble is the best diet for dogs, and this view is advocated by many veterinarians as well as the dog food industry. Another view is that dogs should be fed a diet composed primarily of raw animal meat, bones and carcasses because dogs are like wolves, and this is optimal for their health. An intermediate view is that dogs should be fed a mixed diet of high quality or even organic dog kibble in combination with meat products. Finally, some vegetarians believe that dogs can do very well on diets composed of non-meat foods including grains, vegetables and eggs. Most dog owners hand their pets some food off of the dinner plate, but for many dog owners who rely on bagged kibble the idea that dogs should get a significant proportion of meat, raw or otherwise, probably comes as a bit of a surprise, but it shouldn't. Dogs have been fed whatever leftovers humans have offered for well over 10,000 years, possibly up to 30.000 years, and that has included raw and cooked animal carcass parts that were left over after humans took the parts that they most preferred. It also certainly included seafood, grain based foods, vegetables and dairy products. As such, dogs have survived on extremely varied diets over the last 10,000 thousand years or longer.
The idea that dogs should be fed a diet composed almost exclusively of raw meat, including raw animal carcasses that are predominantly bone, cartilage and sinew has gained popularity primarily due to the notion that dogs are virtually identical to wolves, whose natural diet is heavily composed of raw animal carcasses that they catch or find. There has been very little research to support this notion, but many pet owners and veterinarians claim to have seen positive health results. There is no reason to believe that a diet composed of fresh animal carcasses would be unhealthy for dogs, as long as the carcasses are free of harmful bacteria and parasites. This type of diet is similar to what many ancestral dogs would have lived on during pre-historic times. However, as humans settled down and became more agricultural dog diets would have almost certainly shifted to include grains and vegetables, especially in times of poor hunting.
The list of reasons why dogs are not true carnivores is growing as more research is done. It is well documented that dog teeth and jaw muscles are substantially smaller than those in wolves because dogs have not been under the same selective pressure to be able to kill game and rend the raw carcass. Also, dogs do not hunt in packs efficiently the way wolves do. Very recently the first comprehensive comparison of dog and wolf genetics was completed and has turned up something even more interesting about dogs. Dogs have substantial genetic differences from wolves that make dogs very adept at digesting starchy plant-based foods, whereas carnivores like wolves are not.
There are 3 basic stages of starch digestion including 1) the breakdown of starch to maltose and other complex sugars, 2) the breakdown of complex sugars to glucose and 3) the uptake of glucose from the intestine. The recent genetics study published in Nature by Erik Axelsson and colleagues details how all 3 of these stages in starch digestion have been substantially enhanced in dogs as compared with wolves indicating that dogs are fully capable of handling a starch-based diet. Several of the genetic changes in dogs were not seen in any carnivores studied, and in fact were only seen in herbivores . The scientists showed not just the genes associated with starch metabolism, but also the proteins encoded by several of the genes were increased in dogs relative to wolves. For example, they found that dogs have 28 times greater expression of the alpha-amylase gene in their pancreas as compared with wolves, and a corresponding 4.7 fold increase in alpha-amylase enzyme activity in dog blood as compared with wolves. Alpha-amylase is the enzyme that breaks starch down into maltose and other complex sugars. These findings further undermine the idea that dogs are strict carnivores, and are therefore almost identical to wolves when it comes to an optimal diet.
The other major genetic differences found between dogs and wolves relate to brain development. In fact, the largest number of genetic differences between dogs and wolves were found in genes related to brain development and function, indicating that much of the selection that humans applied to dog breeding was centered around affecting and adjusting dog behaviors relative to wolves. The mounting evidence indicates that our pets are not wolves in dog's clothing, but rather they are the most highly domesticated of all animals on the planet. They are more finely attuned to human life, human behavior and human diets than any other animal. They are certainly no longer pure carnivores.
There is probably no such thing as the optimal dog diet beyond one composed of good quality foods that are varied and contain complete and balanced nutrition with sufficient protein, vitamins and minerals. Based on the latest genetic analyses dogs are not strict carnivores, but have instead become omnivores through their longstanding interactions with humans. This means that dogs can do well on high quality kibble, and on fresh, clean animal carcasses, and on mixed diets, including non-meat diets that include significant protein from sources such as eggs. Dogs have a high capacity to utilize starches as a food source like other omnivores, and most dogs enjoy a good starchy treat just like humans do. Humans have coevolved with dogs for tens of thousands of years, and this symbiotic social relationship is something that humans and wolves currently don't share, and probably never will.