SAGAMIHARA, Japan — Dogs became “man’s best friend” thanks to a gene that lowers stress, according to new research. Researchers in Japan say it made ancient canines more relaxed around people, enabling the special relationship to develop over time.

One of the world’s most favorite pets descends from wolves. However, the domestication of the dog has baffled evolutionary experts for decades.

Now, the Japanese team believes they have solved the riddle. Dogs carry two mutations of a gene known as MC2R (melanocortin 2 receptor). It produces the hormone cortisol – nature’s built-in alarm system which releases when someone experiences fear or anxiety.

“These findings imply MC2R played a role in the domestication of dogs, perhaps by promoting lower levels of stress around humans,” says corresponding author Dr. Miho Nagasawa of Azabu University, according to a statement from SWNS.

Humans and dogs have a long and storied history

Man’s proverbial first best friend was a grey wolf that made contact with its first human companions about 33,000 years ago, somewhere in southeast Asia. About 15,000 years ago, a small pack of domesticated dogs began trotting towards the Middle East and Africa.

The species, known as Canis lupus familiaris, made it to Europe about 10,000 years ago. Humans began to build farmsteads and villages with walls, marking the dawn of modern civilization. Dogs were already there to help keep guard and herd the first flocks and demanding to go for walks. The outlines of this great adventure are written in their DNA, according to the study.

In time, the animals became loved by their owners in the same way as they loved their families. To investigate the phenomenon, Dr. Nagasawa and colleagues ran experiments splitting 624 domestic dogs into ancient and modern (or “general”) breeds.

They found the former felt less attached to the testers than the latter, because of the MC2R variants.

“The dog (Canis familiaris) was the first domesticated animal and hundreds of breeds exist today,” researchers write in Scientific Reports. “During domestication, dogs experienced strong selection for temperament, behavior, and cognitive ability. However, the genetic basis of these abilities is not well-understood.”

“We focused on ancient dog breeds to investigate breed-related differences in social cognitive abilities. In a problem-solving task, ancient breeds showed a lower tendency to look back at humans than other European breeds.”

Which dogs have less of a bond with humans?

The ancient group consisted of those breeds genetically closer to wolves, such as the Akita and Siberian Husky. Others, such as gun dogs, mastiffs, and Jack Russell terriers, are more distantly related.

Blood samples showed changes to the MC2R gene displayed a connection to correctly interpreting gestures and gazing at the experimenters more often. There were no differences in other genes, including those for the “bonding” hormone oxytocin and another linked to hyperactivity.

“The problem-solving test in our study, combined with the result of earlier genome-wide studies of the domestic dogs, indicates that Japanese dogs which have relatively close DNAs to wolves show behavior similar to wolves,” researchers write. “The results of the two-way choice test were similar in both groups of dogs, showing that both groups have similar capabilities in understanding human gestures and adjusting their responses accordingly.”

“In contrast, the General group dogs showed higher eye-contact behavior in the problem-solving test. This suggests that the capability of dogs to understand human commands and adjust their own behavior accordingly, as tested by the two-way choice test, evolved early in the domestication of dogs.”

“The stronger tendency of gazing at humans, as tested by the problem-solving test, was a desirable characteristic that was intentionally chosen for, through human-selected breeding, after dogs had evolved.”

Friendlier dogs were the first to approach humans

Scientists have tracked the modern dog’s emergence back to wolves scavenging leftovers discarded by early humans on the edges of settlements. Over generations, their offspring became bolder still and lived even closer to the people they relied on. In time, humans saw the animals as natural allies and began breeding them to be better hunters and herders.

“The current hypothesis is that ancient wolf individuals that had low levels of fear and aggression started to approach human areas and evolved into dogs,” study authors conclude.

“It may have become necessary through the process of domestication for dogs to gaze at humans for instruction and initiate communication to build a more successful relationship between humans and dogs.”

“Furthermore, as even stray dogs that were not brought up in human households show this characteristic, it has been previously suggested that there is a genetic component involved and our results support this hypothesis.”

There are now more than 400 breeds of domestic dogs around the world.

South West News Service writer Mark Waghorn contributed to this report.

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