Review of Menno Schilthuizen, Darwin Comes to Town: How the Urban Jungle Drives Evolution (Picador, 2018)
Urban wildlife is evolving, and quickly. A striking example is how moths changed color in Britain over the last two centuries. As soot darkened trees in early-industrial Britain, moths with darker wings were better camouflaged from predators than were lighter-colored moths. Before long, dark wings became the dominant coloration. Today, with Britain well past the clean turn in the environmental Kuznets curve, trees in Britain are once again their lighter natural color. The darker moths found themselves being eaten more often than the surviving lighter moths, and lighter wings are once again the dominant coloration.
Noise-filled cities have also caused evolution in bird songs. City birds sing at a noticeably higher pitch than rural birds of the same species, because a lot of city noise happens around the 2-2.5 kHz band where rural birds sing. Many city birds now sing in a higher range closer to 3 kHz, where there is less sonic competition. Experiments with city and rural bird eggs hatched in controlled low-noise conditions show that city birds sing higher instinctually, and not as a learned behavior. It is as though natural selection weeded out the baritones in city birds, leaving only tenors.
Schilthuizen, a Dutch ecologist, compares rapid urban wildlife evolution to Darwin’s finches in the Galapagos, who not only had different beak shapes on each island, but within each island could change beak shapes over just a few generations to match changing food sources. He speculates that if urban evolution continues at its current pace, many common urban plants and animals could eventually become distinct species, as dependent on the urban ecosystem as we humans are.
This book would pair well with Lee Alan Dugatkin and Lyudmila Trut’s How to Tame a Fox, which shows similarly rapid evolution at work in a long-running fox domestication experiment in Russia. I reviewed that book here.
Inertia Wins! 