Quirks & Quarks

Evolution is going uptown as plants and animals adapt to city life

The book 'Darwin Comes To Town' chronicles how many plants and animals have evolved innovative ways of surviving in big cities.

Cities have become an important ecological niche for wildlife to adapt to and colonize

Urban birds have evolved to survive in a new environment. (Frank Liebig, Creative Commons Attribution-Shake Alike 3.0)

If Charles Darwin lived today, he wouldn't have to voyage any further than the London underground to find evolution in action. In the subway tunnels mosquitos have not only adapted to life underground, they are genetically different from one tube station to the next.

This is just one example of how humans aren't the only life form adapting to the bright lights, the fast pace and the new opportunities of the big city. "Cities are like mad scientists creating their own ecological concoctions" says Menno Schilthuizen. He is an evolutionary biologist, ecologist, and professor of biodiversity at Leiden University in the Netherlands, and author of the new book Darwin Comes To Town - How The Urban Jungle Drives Evolution.

Some species - birds and insects for example - arrive in the city under their own steam. Others are brought in by humans - like the exotic plants from around the globe that we fill our gardens with.  In this way, Schilthuizen, points out, cities become a melting pot so a plant from South America can suddenly meet an insect from Europe in a city in China. Urban plants and animals are evolving and adapting to glass, steel and concrete at a surprising rate, and in some incredibly inventive ways.

Crows 'drive' evolution in Japan

Another fascinating example is the way carrion crows have adapted to urban life. These Japanese crows drop walnuts onto rocks from great heights in order to crack them open. But in the 1970 in the Japanese city of Sendai, crows in the city invented a new and more efficient way of solving the walnut shell problem that took advantage of the urban environment.

They waited patiently for cars to stop at pedestrian crossings, then placed walnuts in the path of the tires, recruiting cars as their nut-crackers. Schilthuizen suggests this, and similar behaviours, are examples of selection for urban animals who are creative and less fearful of humans than their rural cousins, and thus better at solving unfamiliar problems.   

Carrion crows like this one in Japan use car tires to crack walnuts. (Pelican, Creative Commons-Share Alike 2.0)

If I can make it there…

Mice, as we know really can make it just about anywhere. But in New York City, mice  are adapting to the individual parks in which they live. Their genes are actually changing to suit the conditions in those specific parks. In Central Park, the mice have evolved genes that help them deal with the very fatty junk food diet in abundance there. New York City mice are just one example of what Schilthuizen says is a "smaller jungle biodiversity" in the new "urban human adapted ecosystem".


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