The Bond Between Humans and Dogs Revealed at the End of a Challenge

KIKUMIZU Takeshi (Professor, Department of Applied Animal Science, Faculty of Veterinary Medicine, Azabu University)

Canines, which have coexisted with humans for over 15,000 years, are considered to be the best partners for humans, and as many as 1,036,000 canines are currently being bred throughout Japan. They are thought to be important not only simply because they are cute, but also for human health and mental health, as well as for human-to-human communication, although the relationship between the two has not been scientifically clarified. Dr. Kikusui of Azabu University's School of Veterinary Medicine hypothesizes that there is a special biological bond between humans and canines, and is engaged in the world's first study of this relationship.

Oxytocin, an affection hormone

Dr. Kikusui, who has loved wild animals since childhood and became a researcher after graduating from veterinary school, was interested in how animal societies, including human societies, are organized. Among animals, canines have a particularly close relationship with humans and are considered the oldest of close friends. However, there has been little research on the biological mechanisms that underlie canine symbiosis with humans. Dr. Kikumizu and his group attempted to prove this hypothesis by measuring "oxytocin," which is important for the formation of animal bonds in previous studies. Oxytocin is a hormone produced in the brain, which has the effect of expanding the mother's uterine opening during childbirth and facilitating delivery. It has also been found to have various psychological effects, such as generating affection and trust toward the partner and reducing stress. Similar effects have been confirmed not only in humans but also in mice and other animals, and it is also called the "affection hormone. It is useful to check changes in oxytocin secretion when examining affection and bonding between mother and child, etc.

A special bond recognized between humans and canines

Dr. Kikusui and his group examined whether canines show an increase in oxytocin concentration in their bodies when they interact with humans. They compared changes in oxytocin concentrations between groups of dogs that gazed at their owners frequently and those that gazed at their owners infrequently, and found an increase in urinary oxytocin concentrations only in the group that gazed frequently during interaction. The results showed that only in the group that stared at the animals often, the concentration of oxytocin in their urine increased during the interaction. Although changes in oxytocin have been observed between mothers and offspring of humans and mice during bond formation, this is the first time that the relationship between oxytocin and bond formation has been confirmed between animals that are not related. The study also found that similar changes were not observed in wolves, which share a common ancestor with dogs but did not choose to coexist with humans. These studies indicate that canines acquired special bond-forming mechanisms during the process of symbiosis with humans. Dr. Kikumizu's research, which was the first to scientifically prove the canine-human bond, was featured on the cover of the renowned scientific journal "Science" and has been attracting public attention with surprise.

Don't be afraid to fail.

The most gratifying moment for me is when I find out that my hypothesis may be correct," says Dr. Kikusui. In the future, he will try to find genes associated with the formation of a special bond between humans and canines, and elucidate the mechanism of bond formation. To do so, they need to accumulate a huge amount of data on the usual behavior of both parties over a long period of 3~4 months after they start keeping canines, and find the key elements in the data. It is no easy task, but Dr. Kikusui's voice is upbeat as he describes the prospects for his research. The more challenging the research, the lower the probability of success. But nothing will change if we are always afraid of failure. If you fail, you just have to correct the problem. Dr. Kikumizu's challenge to visualize invisible bonds will continue in the future.

He will give a lecture at the Science Castle Kanto and Kansai Conferences!