With all its hustle, bustle, concrete, and congestion, they say New York City changes people. And that may be true, but according to a new preprint study posted on bioRxiv, urban life is also changing the city’s mice—right down to their very genes. Mice collected from around the city showed changes in their RNA in genes involved in digestion and metabolism relative to their country counterparts, New Scientist reports. Among these genetic changes the scientists found one involved in the production of omega-3 and omega-6 fatty acids, mirroring a similar change in humans that cropped up around the time our species switched from a hunter-gatherer lifestyle to one based on agriculture. Like humans who consume high quantities of fat, the city mice also showed signs of enlarged livers and genetic changes associated with nonalcoholic fatty liver disease, results the researchers speculate may be from all the human fast food in their diets.