Tag Archives: natural selection

Nature in the Front Yard: Evolution in the City


The voyage on H.M.S. Beagle that led to the theory of evolution took Charles Darwin to many remote places, most famously, the Galápagos Islands, 1000 km off the coast of Ecuador in the Pacific Ocean.

But whether on a Pacific island or in the middle of New York city, the forces of evolution are in operation because science assumes that the universe is a vast single system in which basic laws are consistent no matter where you look. (Quinn et al., 2013)

Actually urban areas are different in one important respect which is that the rapidity of evolutionary forces depends on the “strength of natural selection — the relative benefit that a particular characteristic bestows on its bearer — is strong.” Even a small difference can matter greatly, especially in an urban environment because it is about as extreme and stressful as it is possible to find with its temperatures (warmer than surrounding countryside); its noise (a constant and invasive din that drowns out the usual warning sounds); further the urban landscape is encased in concrete and other substances hostile to the gripping of claws or traction for paws.  Then there are lots of humans, with their tempting trash along with their deadly cats and dogs, their waste that pollutes water, air, and soil.  (Schilthuizen, 2016)

This means that as the world becomes increasingly urbanized, more and more organisms are either being engulfed by urban areas or are gravitating to opportunities found in them.

Biologists therefore are “beginning to realize that the expanding urban sprawl is perhaps not something to be depressed about but something very exciting, as entirely new forms of life are evolving” in them. (Schilthuizen, 2016)

Jason Munshi-South, the director of the Munshi-South “Evolution in the Anthropocene” lab at Fordham University sees New York city as not only one of humanity’s greatest accomplishments but also as the home to native wildlife that are “subject to a grand evolutionary experiment.” (Munshi-South, Ted Ed talk)

Four hundred years ago the territory that makes up modern New York was covered by forest and meadow and was the home to a huge population of white-footed mice.

Four hundred years later the forests and meadows have largely been replaced by city streets, office buildings, multi-storied apartment buildings, and lots and lots of people, with their dangerously fast moving automobiles, noise, food waste, and trash while the white-footed mice are now crowded into the small patches of forest and meadows of the city’s parks. For Munshi-South the mice provide a model of what happens when wild organisms are engulfed by an urban ecosystem.

Advances in genetics have made it possible to identify changes that have occurred in a species because an organism’s genome is a record of its genetic history as well as that of its ancestors.

Genes are short segments of DNA which carry the recipes for creating the amino acids which are the building blocks for the proteins that actually do the cell’s work: its metabolism, its immune response, its reproduction, and so on.

If it happens that a single base pair on a gene changes and the change leads to an advantage for the mouse, for example, more babies, then this change will spread through a population because it will provide the individuals possessing the trait with increased fitness in the competition for survival. (Munshi-South, 2012)

After the examination of several thousand snippets of DNA from the genomes of 191 individual mice taken from 23 sites representing samples of both urban and “wild” environments, and then comparing the results with computer models the investigators were able to trace the history of the population of white-footed mice living in the area around New York.

About 12,000 years ago (coincident with the end of the last North American ice age) when rising sea levels separated Manhattan from the mainland, the genomes of the mice on Manhattan began to diverge from those on the mainland. Then about 400 years ago when Europeans began the settlement that soon became New York, more genetic divergence began to appear as the green space gave way to urban development. As Stephan Harris, a postdoctoral evolutionary biology researcher at Columbia University said, “The exciting thing is that the times of the divergence that we inferred lined up with the arrival of Europeans in New York.” (Netburn, 2016)

In the relatively brief time that New York has been populated by humans, the once genetically similar population of white-footed mice have evolved into genetically distinct populations each inhabiting a different park. The mice in one park are distinctive enough that the home park of a randomly selected New York white-footed mouse can be identified by examining just 18 snippets from its genome.

More significantly, the mice in different parks have developed park-specific traits related to their response to infection, their metabolism, and even their tolerance for environmentally occurring heavy metals like chromium and lead. (Munshi-South, 2012)

You don’t need a berth on the H.M.S. Beagle that will take you around the world to find evolution in action.

There are lots of great opportunities for “citizen science” projects where you can study nature in your home and neighborhood by tracking your local cats or the microscopic mites (Demodox) that are at home in the pores of your skin (yes, yours and mine).

You can find more about these projects at the Your Wild Life website.




Menninger, Holly & Rob Dunn. Your Wild Life: Exploring biodiversity in our daily lives.

Munshi-South, Jason (2017). Evolution in Anthropocene. Retrieved from http://nycevolution.org


Munshi-South, Jason (2012). TED Ed.  Evolution in the Big City, retrieved from http://ed.ted.com/lessons/evolution-in-a-big-city


Netburn, D. (2016c). Why the City Mouse and the Country Mouse Have Different Genes. Los Angeles Times. Retrieved from http://www.latimes.com/science/sciencenow/la-sci-sn-city-mouse-20160415-story.html


Schilthuizen, Menno (2016). Evolution is Happening Faster Than We Thought.  New York Times, Sunday Review, July 23, 2016. Retrieved from https://www.nytimes.com/2016/07/24/opinion/sunday/evolution-is-happening-faster-than-we-thought.html?_r=0#st


Quinn, Helen R., Schweingruber, Heidi, Keller, Thomas, & others, A. A Framework for K-12 Science Education: Practices, Crosscutting Concepts, and Core Ideas. Washington, DC: National Research Council of the National Academies. Retrieved from http://www.nap.edu



evolution, urban ecosystem, fitness, gene, genome, genetics, white-footed mouse, New York, natural selection, citizen science, project-based curriculum