Mice to men: everywhere you go, we'll follow

In 2016, nearly half of all calls to pest control agencies were pleas for help against rising populations of Mus musculus domesticus, the house mouse. But the origins of this battle far predate our potato chip crumbs and central heating.

A study published Monday in the journal Proceedings of the National Academy of Sciences finds that humans and the common house mouse have been coexisting for 15,000 years, longer than humans have been farming. By settling down and storing food, hunter-gatherers created a niche for mice that continues to this day.

Cornell University biologist Jeremy Searle in Ithaca, N.Y., who is not connected with the research, said it gave a fascinating insight into a pre-agriculture association of house mice with humans.

"The important thing is a settled existence with storage of seeds," Dr. Searle told the BBC. "It doesn't have to be cultivated grain; it can be wild foodstuffs collected by hunter-gatherers."

The Natufian people, who lived between 12,500 and 9,500 BCE in modern-day Israel, Lebanon, and Syria, were among the first to create these conditions. Prior to the rise of agriculture, they had set up semi-permanent base camps to kill game and pluck grains and fruits from the surrounding countryside.

In the remains of these settlements, the study’s authors found fossilized teeth from mice dating back 15,000 years. There, they could find ample stores of food and no domesticated cats or dogs – or mousetraps – that would await them in later dwellings.

Pre-agricultural groups like these may have had little reason to kill mice. To understand how the Natufians may have viewed the rodents, the study’s authors looked at modern-day Maasai villages in Kenya and Tanzania, whose pastoral residents periodically re-locate and paid little heed to their tiny rodent followers in a relationship the study's authors describe as "commensal."

“This means that the interaction was one-sided: mice were benefitting, but humans were neutral – neither benefitting nor being harmed,” explained study co-author Lior Weissbrod, according to Gizmodo.  

Stronger competition may have come from a related species of mouse, the short-tailed Mus macedonicus. Analyzing both the fossil record and modern-day Maasai dwellings, the study’s authors believe that the latter species eventually focused on exploiting wild resources, whereas the house mouse found a “niche” in human dwellings.

There, it could go on to pilfer some of the first grains painstakingly harvested by farmers – and spread, despite humans’ best wishes, around the world. “They began to spread from the Levant with Neolithic societies to Europe, in a process that took thousands of years,” said Dr. Weissbrod. “From Europe, mice spread with humans to colonize new continents.”

And beyond; since the dawn of the space age mice have been frequent astronauts and have served as test subjects for new biomedical practices such as genetic engineering. Having first viewed mice with indifference, then spent millennia trying to kill them, humans are now finding new, more positive roles for the house mouse.