A team of researchers from the American Museum of Natural History and the Smithsonian National Museum of Natural History analyzed more than 2,700 genomes of dogs, wolves, and other canids from public genetic databases.
Their work, published in
Proceedings of the National Academy of Sciences, indicates that the majority of modern dogs carry traces of wolf DNA in their genomes, resulting from hybridization events that occurred approximately 1,000 generations ago. These genetic fragments influence various traits, such as size, olfactory abilities, and certain behavioral tendencies, helping dogs adapt to diverse human environments.
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The study highlighted significant variations in wolf ancestry levels across breeds. For example, Czechoslovakian Wolfdogs and Saarloos Wolfdogs, which were intentionally crossed with wolves, show the highest rates, ranging from 23 to 40 percent. Among more common breeds, the Grand Anglo-Français Tricolore displays about 5 percent wolf ancestry, while smaller dogs like the Chihuahua have around 0.2 percent. These differences are explained by distinct breeding histories, with some involving recent crosses to enhance working abilities.
Behavioral descriptions of breeds, provided by kennel clubs, show correlations with the amount of wolf DNA. Dogs with low wolf ancestry are often described as friendly, easy to train, and affectionate, while those with higher ancestry are perceived as independent, wary of strangers, and territorial. These terms reflect human interpretations, and it is not yet certain whether genes derived from wolves directly control these traits, but this opens avenues for future research on animal behavior.
Some genetic adaptations inherited from wolves help dogs survive in specific conditions. Village dogs, for example, possess enriched genes related to olfactory receptors, which improves their ability to detect food sources in human waste. Similarly, Tibetan Mastiffs have acquired genes from Tibetan wolves, allowing them to tolerate low oxygen levels at high altitudes, such as in the Himalayan regions.
Researchers observed that large-sized breeds and those historically used for specialized work, such as Arctic sled dogs or hunting dogs, tend to have higher levels of wolf ancestry. In contrast, breeds like terriers and pointing dogs generally show less. Exceptions exist, such as some mastiffs that show no trace of wolf DNA, illustrating the genetic diversity within canine populations.
Hybridization and its impact on evolution
Hybridization is a natural process where two distinct species or populations crossbreed, leading to gene exchange. In canids, this occurs when wolves and dogs mate, although it is rare after domestication. These events introduce new genetic variants into populations, which can increase diversity and promote adaptation to new environments.
In the case of dogs, hybridization with wolves allowed the introduction of beneficial genes, such as those related to altitude tolerance or sense of smell. This phenomenon, called genetic introgression, shows that barriers between species are not always strict and that genomes can incorporate foreign DNA without losing their main characteristics. This contradicts the idea that dogs must be genetically pure to remain domestic animals.
Modern genomic studies, using high-throughput sequencing, can detect these traces of hybridization even if they are weak. By analyzing thousands of genomes, researchers can trace evolutionary history and identify when these crosses occurred. This helps understand how species adapt and evolve over time, with implications for conservation and evolutionary biology.