A new investigation showed that mice have lived among humans for more than 15,000 years, according to a newly discovered set of fossils. The new findings point to the fact that mice could have started living with humans since the moment the latter began to build houses and settle down in particular places.

The study was published Monday in the Proceedings of the National Academy of Sciences, and it showed that these little companions are not just invaders. In fact, mice have been evolving along with humans since they stopped being nomads and started to build semi-permanent homes.

House Mouse
There is a healthy relationship between both species, according to study author Fiona Marshall. She says that this relationship is a clear example of an animal-human commensalism, which is a relation where an animal can get benefits from the human species without affecting it considerably. Image credit: iStock.

The study showed that one of the first human robust communities called the Natufians were able to settle down in the Levant, an Eastern zone located in the Mediterranean. This community that lived at the end of the Ice Age built several semi-permanent homes made out of stones and rocks.

In these houses, the researchers found the presence of the known Mus musculus domesticus, which back then was only an emerging species. These animals took advantage of these homes as they fed on scraps and got protection from many predators, helping on the sustainability of the species.

A long lasting fact got discredited after the study publication

All previous investigations regarding mice and their relationship with humans showed that this species began to live near us since the creation of agriculture about 12,000 years ago. Scientists consistently stated that the presence of mice was due to the human’s ability to farm and that any earlier relationship between both was non-existent.

The investigation team found mice teeth among the before mentioned semi-permanent human houses at the Mediterranean. According to Miloš Macholán, an evolutionary biologist and co-author of The Evolution of the House Mousethese new findings are crucial even for understanding our own evolution processes. He told National Geographic that looking for mice fossils might teach investigators about important parts of human history regarding early settlement attempts.

Mouse and cat/ House Mouse
The finding of more mice molars could even fill archeological gaps present in current studies concerning human work mechanisms’ evolution. Image credit: The Alley.

In this issue, this new study opens the possibilities to analyze the human transition between being a hunter-gatherer and being a farmer more than 10,000 years ago.

“I’d say it’s important to understand that mice have been accompanying us for a very long time,” says study leader Lior Weissbrod, a zooarchaeologist at the University of Haifa in Israel. “We’ve been changing them and they’ve been changing us in ways that are not immediately apparent.”

Two different types of mice and one long-term human relationship

The Mus musculus domesticus, ergo, the ancestor of the house mouse we know today, was not the only type of mouse found by investigators in the Levant zone. The area that now includes parts of Israel, Lebanon, and Syria, also hosted fossils belonging to the second type of mice called the Mus macedonicus, and its presence confirms the scientists’ hypothesis.

The Mus macedonicus is a type of mice that does not get along so well with human species. After exhaustive examination, the investigation team discovered that the molars present in the studied area also belong to that species, also known as the short-tailed mouse. This rodent is wilder and cannot live along with humans, even when it was found near Natufians settlements at the Levant.

House Mouse
A female western house mouse (Mus musculus domesticus). Image credit: MPI for Evolutionary Biology.

The house mouse was probably attracted for human settlements as Natufians had to store high amounts of food to survive through its sedentary period in the zone, according to lead author Weissbrod. However, the short-tailed mice were not attracted to those settlements as the molar fossils found in the stone homes that belonged to that species started to diminish considerably in proportion to human presence.

The climatic conditions affected Natufians at the time of staying or leaving particular zones for specific periods, and researchers discovered that the house mice were always present in the settlements while the short-tailed ones often avoided humans.

“Nowadays, thanks to this relationship, house mice have colonized almost every corner of the globe to become almost as ubiquitous as humans and also one of the most invasive mammalian species,” said Dr. Thomas Cucchi of Museum of National Natural History of Paris.

The final prove that sustained the study’s theory came after analyzing the mice-human relationship in a modern semi-nomadic community called the Maasai located in Kenya. The results showed that every time the persons of the tribe started to move, the presence of the short-tailed mice species began to dominate over the common house mouse, and when they settled for more than a month, it was the other way around. Researchers were amazed by the fact this relationship behaves quite similar than 15,000 years ago.

Source: National Geographic