This footage captures the behavior of a selective-bred friendly mouse and compares it with that of non-selective-bred mouse. (Provided by the National Institute of Genetics)

What makes domestic animals such as dogs tame could be in their genes, a Japanese research team discovered after breeding a family of mice that are friendly to humans.

The team from the National Institute of Genetics came to the conclusion as a result of cross-breeding of mice for generations, which led them to identify the part of the mouse genome that could be related to their tameness.

“This research could unravel the reason why many wild animals cannot be domesticated,” said Tsuyoshi Koide, an associate professor of behavior genetics at the institute.

The team's findings were published in British journal Scientific Reports on July 4.

Koide and his team started the experiments by selecting wild mice that are relatively unafraid of humans, and cross-bred them. The team repeated the selective breeding for 12 generations in four years by choosing 32 mice that displayed tameness from each generation.

As a result, the offspring became extra-friendly to humans, and would spontaneously approach people when they extended their hands to them.

According to the researchers, pet mice tend to be tame and tolerate being touched, but not many would come close to a human spontaneously.

The team compared the genomes of the family of selective-bred friendly mice and non-selective-bred mice and identified genes that may be related to the tameness of their “personalities.”

They also found out those particular genes are present in dogs.