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dogs They were the first of any species to be domesticated by people, and they have been a constant part of human life for millennia.
Domesticated species are plants and animals that have evolved to live alongside humans, providing us with almost all of our food and many other benefits. Dogs provide protection, hunting assistance, companionshipWool for transportation and even for weaving blankets.
dogs evolved gray wolvesBut scientists debate where, when, and how often dogs were domesticated.
Ancient dna Evidence suggests that domestication occurred twice in eastern and western Eurasia, before the groups eventually mixed. That mixed population was the ancestor of all dogs alive today.
Molecular clock analysis of the DNA of hundreds of modern and ancient dogs shows that they were domesticated about 20,000 to 22,000 years ago, when large ice sheets covered much of Eurasia and North America.
first dog Identified in the archaeological record is a 14,000-year-old puppy that was found in Bonn-Oberkassel, Germany, but it can be difficult to tell based on the bones whether the animal was an early domestic dog or a wild wolf.
Despite the shared history of dogs and wolves, scientists have long thought that these two species rarely mate and produce hybrid offspring.
As an evolutionary biologist and a molecular anthropologist who studies domestic plants and animals, we wanted to take a fresh look at whether dog-wolf hybridization is really so unusual.
little interbreeding in the wild
Dogs are not descendants of modern wolves at all. Rather, both dogs and wolves living today descended from a shared ancient wolf population that lived alongside woolly mammoths and cave bears.
In most domesticated species, there are often clear, documented patterns of gene flow between animals living alongside humans and their wild counterparts. Where the habitats of wild and domesticated animals overlap, they can breed with each other to produce hybrid offspring. In these cases, genes from wild animals translate into genetic variations of domesticated populations.
For example, pigs were domesticated in the Near East 10,000 years ago. But when early farmers brought them to Europe, they hybridized with local wild boars so many times that almost all of their Near Eastern DNA was altered.
Similar patterns can be seen in the endangered wild Anatolian and Cyprus mouflon, which researchers have found have a high proportion of domestic sheep DNA in their genomes. It is common to find no evidence of wild and domesticated animals interbreeding and sharing genetic material over time.
That wolves and dogs do not show that distinct pattern is surprising, since they live in overlapping ranges and can interbreed freely.
However, the behavior of dogs and wolves is completely different, with wolves generally organized around a family pack structure and dogs dependent on humans. When hybridization occurs, it occurs when human activities – such as habitat encroachment and hunting – disrupt pack dynamics, causing female wolves to strike out on their own and breed with male dogs.
People deliberately bred some “wolf dog” hybrids in the 20th century, but these are considered exceptions.
Small but traceable wolf lineage
To investigate how much gene flow actually occurred between dogs and wolves after domestication, we analyzed 2,693 previously published genomes, using a large-scale publicly available dataset.
About the authors
Audrey T. Lynn is a Research Associate in Anthropology at the Smithsonian Institution.
Logan Kistler is Curator of Archaeobotany and Archaeogenomics at the National Museum of Natural History, Smithsonian Institution.
This article was first published Conversation And it is republished under a Creative Commons license. read the original article,
These included 146 ancient dogs and wolves dating back about 100,000 years. We also looked at 1,872 modern dogs, including Golden Retrievers, Chihuahuas, Malamutes, Basenjis and other well-known breeds, as well as more unusual breeds from around the world like the Caucasian Ovcharka and the Swedish Vallhund.
In the end, we included the genomes of about 300 “rural dogs.” These are not pets but free-living animals that depend on their close relationship with the human environment.
We traced the evolutionary history of all these canids by looking at maternal lineages through their mitochondrial genomes and paternal lineages through their Y chromosomes. We used highly sensitive computational methods to dive into the nuclear genomes of dogs and wolves – that is, the genetic material present in the nuclei of their cells.
We found the presence of wild wolf genes in most dog genomes and the presence of dog genes in about half of the wild wolf genomes.
The wolf mark was small but was present as small, almost imperceptible fragments of continuous wolf DNA in the dog’s chromosomes. About two-thirds of the purebred dogs in our sample had wolf genes from crossbreeding that occurred about 800 generations ago, on average.
While our results showed that large, working dogs – such as sled dogs and large guard dogs that protect livestock – generally have more wolf ancestry, the patterns are not universal.
Some giant breeds, like the Saint Bernard, lack wolf DNA entirely, but the tiny Chihuahua retains detectable wolf ancestry at 0.2 percent of its genome. Terriers and scent hounds generally fall on the lower end of the spectrum of wolf genes.
To our surprise, the village dogs we tested had fragments of wolf DNA in their genomes. why will? Country dogs are free-living animals that make up about half of the world’s dogs. Their lives can be difficult, with short life expectancy and high infant mortality rates. Village dogs have also been associated with pathogenic diseases, including rabies and canine distemper, making them a public health concern.
More than expected by chance, the segments of wolf DNA we found in the genomes of village dogs included genes related to olfactory receptors. We speculate that olfactory abilities influenced by wolf genes may have helped these free-living dogs survive in harsh, unstable environments.
interbreeding of dogs and wolves
Because dogs evolved from wolves, all of the dog DNA is essentially wolf DNA. So when we’re talking about small pieces of wolf DNA in the dog genome, we’re not referring to the original wolf gene pool that has been circulating for the last 20,000 years, but rather evidence of dogs and wolves continuing to interbreed in later times.
A wolf-dog hybrid with one of each type of parent will have 50 percent dog and 50 percent wolf DNA. If that hybrid then survived and mated with dogs, its offspring would be 25 percent wolf, and so on, until we see only small fragments of wolf DNA present.
The situation is similar with the human genome: Neanderthals and humans shared a common ancestor about five million years ago. However, Neanderthals and our species, Homo sapiens, overlapped and interbred in Eurasia as recently as a few thousand generations ago, shortly before the Neanderthals disappeared.
Scientists can see small pieces of it Neanderthal DNA in most living humans In the same way we can see wolf genes within most dogs.
Our study updates the previously held belief that hybridization between dogs and wolves is rare; Genetic imprints appear in the interactions between these two species.
Hybridization with free-roaming dogs is considered a threat to conservation efforts for endangered wolves, including the Iberian, Italian, and Himalayan wolves. However, there is also evidence that dog-wolf mixing may provide genetic advantages to wolves as they adapt to environments that are increasingly shaped by humans.
Although dogs evolved as human companions, wolves have served as their genetic lifeline. When dogs faced evolutionary challenges such as how to survive in harsh climates, how to search for food on roads or how to protect livestock, they appear to have been able to use their wolf ancestry as part of their evolutionary survival kit.