Matthew Combs is a graduate student at Fordham University in New York City studying ecology, which is the science of interactions between animals and their environment. He recently found that rats living in the uptown neighborhoods of Manhattan have different genes from those living below 14th Street, or downtown.
Why? The midtown area of Manhattan lacks abundant food and shelter, preventing uptown rats and downtown rats from mating and exchanging genes. That means that Combs can test the DNA of any rat and predict where it lives. “Just like a desert or a jungle is a type of ecosystem, the city provides a very specific type of environment for animals,” says Combs.