pet dogs (The familiar lupus) the oldest and most popular pets; modern dog breeds were tamed by human society over 10,000 years ago! However, the process of domestication is yet to be elucidated. Less aggressive than wolves, closer to humans, dogs are also able to communicate with them. What biological mechanisms underlie this fundamental difference? A new study sheds light on genetic differences.
Today there are more than 400 breeds of domestic dogs. Dogs are believed to have been bred for their proximity to humans, physical traits, demeanor, and, more broadly, their ability to form social relationships. However, the genetic basis of these abilities is not well understood, and a group of specialists from the Department of Veterinary Medicine at Azabu University in Japan took up this issue.
” There is no doubt that these behavioral adaptations, including obedience and the ability to communicate with people, are important factors in allowing the dog to integrate into human society. ‘, the researchers write. Scientific reports. They found that two mutations in a specific gene that is involved in the production of cortisol may have played a role in the domestication of dogs, allowing them to develop social cognitive skills to interact and socialize with humans.
Social abilities associated with the endocrine system
Namely, animal behavior, especially social behavior, is modulated and influenced by the action of various hormones in the brain. For example, glucocorticoids (cortisone and cortisol) are hormones positively associated with anxiety and social avoidance. Therefore, they may have played a role in the domestication process, as did oxytocin. The latter is a hormone widely involved in bonding between a female and her offspring in mammals. Research has shown that oxytocin can also mediate interspecies relationships; this is what allows dogs to respond to human social cues, such as being pointed.
Genomic studies have identified a list of genes that were positively selected during domestication; the functions of these genes are very diverse (digestion, reproduction, neurological processes, etc.). ” Some of these choices may have affected the endocrine system, resulting in domestic dogs acquiring their unique behaviors through the process of domestication. “, the researchers note. Therefore, they further investigated the role of cortisol and oxytocin in this process.
Miho Nagasawa and his colleagues began by studying the social and cognitive interactions of 624 domestic dogs, giving them two tasks. In the first, the dog had to decide which of two bowls the food was hidden in based on cues such as staring, pointing, and tapping provided by the experimenters. This task was designed to test the dog’s understanding of gestures and human communication.
In the second task, the dog was given a problem-solving test that involved trying to open the container to access the food. During the task, the frequency and duration of the dog’s gaze at the experimenters was measured to assess social attachment to the human. The dogs were divided into two groups based on their breed: the old breed group, made up of breeds considered genetically closer to wolves, such as the Akita and the Siberian Husky; and the general group, which includes all other races.
Attachment resulting from genetic mutations
From this experiment, it appeared that during the problem-solving task, older breed dogs showed a longer delay before looking at the experimenters; in addition, they were less likely to look at humans than other races, indicating that they were less attached to them overall. Researchers, on the other hand, report no significant race-related differences during the first task, neither in their speed of correct response nor in their ability to understand human gestures and signals.
” We hypothesized that cortisol’s regulation of social tolerance and fearless response to humans may have been the most important turning point in dog domestication. However, lower cortisol levels alone cannot explain the ability of dogs to understand human communication cues and form social bonds, so the team suspected that oxytocin was also involved in the domestication process.
They then examined, in each of the two groups, genetic polymorphisms of oxytocin, oxytocin receptor, melanocortin 2 receptor (MC2R), and a gene associated with Williams-Buren syndrome as candidate genes for dog domestication. In humans, Williams-Buren syndrome is a congenital disorder characterized, among other developmental difficulties, by hypersocial behavior; they have a strong need to love and be loved. However, unlike wolves, domestic dogs have specific genetic inserts at the level of chromosome 6, a critical region of this syndrome, which explains their extreme sociability.
Analysis of the data shows that two mutations in the MC2R gene, which is involved in the production of cortisol, are associated with both the correct interpretation of gestures in the first task, and with a more frequent look at experimenters when solving problems. Thus, this gene may have played a role in the domestication of dogs, possibly helping to reduce stress levels in the company of people.
However, further research is needed to confirm this conclusion. The team believes that the social cognitive skills of domestic dogs cannot be fully explained by the genes identified here alone, but must be controlled by other genes whose effects will need to be determined.