Charles Darwin stepped foot from the intrepid HMS Beagle onto the shores of Galapagos in 1835, where his studies led him to describe evolution and natural selection. Since then, scientists have been enamored with his theories, confirming and amending them along the way.
Evolution, however, is a continuous process, occurring over generations. We’ve always believed that evolution occurs far too slowly for study in one human lifetime.
But science is challenging our notions, as it so often does. In this case, it’s the animals with whom we share our sprawling cities that are teaching modern researchers how quickly evolution can happen.
Scientist have noticed, for example, that urban-dwelling birds have adapted several key differences from their rural cousins. Their bills are stockier, probably to enable easier foraging through debris and trash. Their calls are sung at a higher pitch, likely to overcome the constant background noise of the city.
The key to this rapid evolution is the merciless natural selection that animals encounter in cities. Temperatures in urban areas can be up to 10 degrees higher than in the rural areas. There’s traffic, a source of continuous noise, while automobiles themselves are a dangerous barrier to movement; there’s concrete that covers everything, eliminating burrowing and nesting grounds for many species. And then there’s the ubiquitous pollution, our lovely contribution to it all.
With all these catalysts for natural selection, something interesting is happening: instead of dying out, species are adapting before our eyes. Fordham University’s Jason Munshi-South studies the populations of white-footed mice in New York City. These native mice once lived everywhere, but became confined to the pockets of trees left in parks. The mice have evolved park-specific adaptabilities, such as genes for heavy metal tolerance (where the soil is contaminated with lead or chromium), and even increased immune response.
Urban flora is also evolving rapidly. A weed in Montpellier, France, called Crepis sancta has evolved a heavier seed, which falls directly to the ground (where the plant is already growing) instead of drifting in the wind – where it likely land on concrete.
Spiders in Vienna have developed the technique of building webs near streetlights to attract prey; contrastingly, some moths have learned resist the irresistible lightbulb.
It’s a fascinating look at how humans are accelerating natural selection. As our cities expand, so too will the need for adaptability in the animal kingdom. The examples here are certainly not comprehensive – leave a comment if you’ve noticed any animal adaptations in your own modern environment.