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To thrive in rapidly changing urban areas, plants and animals are evolving at astonishing rates

Darwin Comes to Town: How the Urban Jungle Drives Evolution

Menno Schilthuizen
Picador
2018
304 pp/
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Metal-excreting pigeons, pigeon-eating catfish, cigarette-wielding sparrows, soprano-voiced great tits: The modern city is a fantastical menagerie of the odd and unexpected. Through a series of 20 short but connected chapters that mix natural history vignettes, interviews with visionary scientists, and visits to childhood haunts, science journalist and biology professor Menno Schilthuizen introduces readers to the striking facts of ongoing urban evolution in Darwin Comes to Town. But while the prose may be playful (“Cut to the Hollywood bobcats”), the underlying message may cause discomfort.

Two cross-cutting ideas permeate the book. The first is the notion of rampaging sameness. Because we are incessant, but messy, busybodies, Schilthuizen argues, we scatter species across countries and continents. And we move most among cities.

The author does a fine job of conveying this urban sameness when describing a scene along an estuary in Singapore: the house crows and the mynas feeding in the cow grass, the apple snails laying eggs among the mimosa, the red-eared slider turtles dipping into the water, and the peacock bass breaking the surface for a gulp of air. Every one of the species he describes is a non-native, every one is found in countless other cities the world over, and every one is at home in its new habitat. Schilthuizen has even borrowed a name from parasitology for them: anthropophiles.

And the reason for this biological sameness is urban sameness. Cities around the world produce the same sorts of garbage and the same sorts of noise, house the same sorts of skyscrapers, and produce the same fragmented landscapes. They can even generate the same sort of weather via particulate pollution and the heat-island effect.

The book’s second major theme is that rapid change is an enduring part of the urban environment. Urban plants and animals evolve and adapt to their novel urban surroundings at remarkable speed. The city pigeons’ darker, more melanic feathers sequester poisonous metals; the great tit’s new soprano notes are better heard above the city din; and city moths in Europe have become less attracted to deadly artificial lights.

Indeed, the realization that adaptive evolutionary change occurring on human time-scales in multicellular species is common, rather than rare, is both fairly new and fairly profound. The ubiquity of the phenomenon has even given rise to a new field known as eco-evolutionary dynamics (1).

PGIAM/ISTOCKPHOTO.COM

Dark pigments in a pigeon’s feathers may help it sequester toxic metals in polluted cities.

It is now clear that adaptation can be so fast as to affect the very environment that sets the stage for those adaptations, leading to possible merry-go-rounds of organism-environment-organism changes through time. The implications of this are still not fully known, but it’s safe to assume that this is not what Darwin envisioned from his seat in the Kent countryside. (Perhaps he should have come up to the city more often.)

The fact that urban evolution is surprisingly fast also supports one of the radical ideas promulgated at the very end of this book: a vision of a city engineered to encourage the continued adaptive evolution of other species. We could, Schilthuizen argues, become evolution engineers, promoting the evolution of traits that will stand both us and our anthropophiles in good stead, such as using thriving non-native plants to populate green roofs or actively suppressing genetic mixing. As lineages continue to evolve, we can reengineer their environments as needed.

A project of engineering urban evolution is likely to pique interest, discussion, and perhaps even directed research. But this is clearly a view of nature that is more Abu Dhabi than Amazon rainforest, more engineering than awe.

Schilthuizen tacitly acknowledges that we have bent Earth to our bidding and that the rest of its inhabitants will either adapt or perish. This is undoubtedly true (2). But his view of the future replaces a nature where we decidedly do not meddle (3) with one where we decidedly do. For some, this will seem the very opposite of natural. And that dissonance may put a sting in an otherwise fascinating tale.

References

  1. A. P. Hendry, Eco-evolutionary Dynamics (Princeton Univ. Press, Princeton, 2016)

  2. C. D. Thomas, Inheritors of the Earth (Public Affairs, New York, 2017).

  3. D.S. Maier, What’s So Good About Biodiversity? (Springer Verlag, Berlin, 2012)

About the author

The reviewer is at the Department of Biological Sciences, Simon Fraser University, Burnaby, BC V5A 1S6, Canada.