House mice outcompeted their wild relatives to become domesticated as soon as long-term human settlements appeared, some 5000 years before agriculture took hold.
The advent of farming marks a huge change in human populations – a change in diet, social structure and a switch to a more sedentary lifestyle. Agriculture also had a profound impact on wild animals, and is thought to have led to the domestication of many species, from wolves to cattle and chickens. But other species became domesticated accidentally – as humans started storing grain for lengthy periods of time, the house mouse adapted to thrive in this new ecosystem. Now, a new study shows that it was our sedentary lifestyle, not agriculture, that domesticated one of our most prolific pests.
A study published in The Proceedings of the National Academy of Sciences compared the shape of house mouse teeth through a nearly 200,000-year record of fossils from the Levant, in the eastern Mediterranean, where the earliest human settlements were formed. They found that the first mice began living with humans around 15,000 years ago, with these new ‘commensal mice’ doing particularly well during periods when humans lived in more stable settlements.
The road to modern habitation was far from smooth, however, and the study found evidence that humans went through nomadic phases as well as more sedentary ones, and that the success of the commensal house mouse fluctuated in line with these changes.
They also looked at how modern mice interact with small villages in Africa, collecting nearly 200 mice from six settlements in Kenya. They found that modern populations, too, experience fluctuating population dynamics that relate to how sedentary local human populations are. House mice do best when humans are more settled, but start to be out-competed by wild mice when humans are on the move.
This study shows that it was human behaviour, namely sedentism, that drove the self-domestication of the house mouse, not agriculture itself.
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