Here’s a story about the first friendly dog, which may or may not be genuine. Ten thousand years ago, night falls on a human village. A family gathers around a campfire at the end of a long day of farming. Some venison, corn, bread, and maybe even a few cups of mead are on the table as they relax. They hear a rustling sound in the shadows, and they look around to see what it is. As they look around, they see the wolf’s emerald eyes gleaming.
People may be shocked, but they aren’t afraid. For years, residents have spotted a strange pack of wolves hanging about the waste pile just outside the settlement, scavenging among the food scraps. Since they’ve never harmed anyone, the animals keep their distance. A wolf has never approached so near before. A cocked head and a slow approach to the fire are all it does as it nears. A piece of bread is thrown to the ground.
Dogs are the wolves that mooched, a fable that resonates with me as a new dog owner. They wanted us, they found a way to get to know us, and they eventually won us over to be their lifelong best friends. The scavenger hypothesis,’ a widely held scientific notion, posits that dogs evolved from scavenging animals. By no means, though, is it the only one.
People may have purposely trapped wolf pups to teach them as sentinels or hunters, according to another notion. Still, some researchers believe that humans learned to hunt by watching wolves as wolves and humans co-evolved. According to evolutionary biology professor Bob Wayne, “there are as many specific situations as there are scientists studying in this field,” he says. In light of the fact that we’re looking back at such a lengthy period of time, we can only speculate.
According to the vast majority of genetic evidence, dogs first appeared in the Neolithic period, as people transitioned from hunting and gathering to farming. However, some dog fossils date back as far as 33,000 years, making them among the oldest ever found. The origins of dog domestication are likewise open to debate. Anywhere from the Middle East to China to Siberia is possible.
The genetic sequences of current dogs and wolves were compared by Erik Axelsson and colleagues at Uppsala University in Sweden to understand more about canine evolution. Dogs and wolves have unique differences in genes involved in the development of the brain and the digestion of starch, according to a study published today in Nature.
60 dogs from 14 breeds were used in the study, including the shaggy bearded collie, the super-short drever, and the slimline Swedish elkhound, which has characteristics similar to a wolf. A master ‘dog’ reference was created by combining the genomic sequences of each individual dog. Using 12 wolves from seven nations, they compared this genome to a master “wolf” genome.
Approximately 36 distinct variations were discovered across the genome in dogs and wolves. According to Axelsson, despite the fact that each region contains three or four genes, only one gene is likely to be responsible for the variation. Many of the 122 candidate genes have similar functions in the body. Eight of the genes are involved in the development of the brain and neurological system, for example.
The well-known behavioral differences between dogs and wolves — essentially, that wolves become violent and dogs do not — make brain development genes interesting.
Young wolves and dogs share many of the same characteristics, such as running around in circles, playing, and looking adorable. Nicholas Dodman, a professor at Tufts University’s veterinary school, claims that young wolf puppies even bark like dogs. Suddenly, though, the wolf has matured into an aloof, lean, and distrustful predator.
As domesticated animals mature, they appear to take on a more childlike form, with larger eyes, smaller faces, and less aggressive demeanors, as if they were still children. It’s possible, adds Axelsson, that slowing down an animal’s growth is one regular method for domesticating a species. “The fact that the nervous system’s development is altered here lends some credence to this notion.”
Most of his new research is focused on genes that control digestion. The researchers observed genetic differences in each of the three phases of starch digestion in dogs. A gene called AMY2B is responsible for producing alpha-amylase, an enzyme that breaks down starch into maltose in the pancreas. There are two copies of AMY2B in the wolf genome, but dogs might have anywhere from four to 30 copies in their genome. Alpha-amylase levels in pancreatic tissue from dogs are 28 times greater than those in blood, according to the study.
Wolves, on the other hand, lack the ability to metabolize carbohydrates. I had no idea what to expect from this. Axelsson recalls, “No one had predicted it.”
According to Axelsson, his findings are consistent with the scavenging theory. Werewolves interested in consuming human flesh would have had to develop trusting traits and starch-digesting processes. Axelsson hypothesizes that “selection pressures to affect both behavior and the digestive system” may have occurred simultaneously.
Other scientists, on the other hand, believe that these alterations could have occurred at a different moment in time. A few thousand years before humans had any starches to speak of, it’s feasible, even probable, that wolves started hanging out in our dumps. Future studies must compare DNA from a wider variety of dog breeds and from dog fossils in order to be certain.
Here are two things I’m taking away from this study, in the midst of all the speculation: For pet owners, this is a useful piece of advice. Is the fashionable (and pricey) raw-meat diet right for you? Is this a good sign? Wayne thinks so. In dogs, carbohydrate digestion is facilitated by a unique digestive system.
A further benefit of dog studies is that we may learn a lot about our own history and genetic evolution from our furry friends. Get this: Alpha-amylase gene mutations have been found in humans, as well, based on human investigations. Humans and other organisms have evolved in tandem with the emergence of agriculture, according to Axelsson. “It’s eye-opening to see how drastic the shift must have been.”
Cre: National Geographic
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