Evolution in urban areas


[POST BY Janna Verwijs and Francisca Langstraat]

During our history, mankind managed to employ evolutionary processes for their own gain. While we did not create new species, we did change the characteristics of some organisms by domesticating them. Animals like horses, cattle, dogs, rabbits, pigeons, chickens, as well as certain plant-species, were all changed to our benefit. We made them bigger, faster or more productive, altering their characteristics by selection.

We are only now starting to realise that we influence the evolution of the non-domesticated around us as well. By building cities, we change the landscape and create habitats that might be more beneficial for new, adapted individuals. Spiders in cities are bigger than the ones in the countryside. Earthworms in urban areas have a bigger tolerance for metals. Some birds, for example pigeons, breed all year round in the cities, because of the higher temperatures and the steady food-supply. Smaller songbirds like tits are influenced by city noises in their singing behaviour. They change the frequency of their songs in order to not be overpowered by the other sounds in the city. This gives them an evolutionary advantage over non-adapted members of the same species.

These changes on it self are not good or bad. They are adaptations to a new environment. The same evolutionary processes that have been going on for millions of years cause these species to adapt like they have always done before. They are, however, an indication of the impact that humankind has on this planet.

More reading: Fearless birds and big city spiders: Is urbanisation pushing Earth’s evolution to a tipping point? sciencedaily.com