People often consider evolution to be a process that occurs in nature in the background of human society. But evolution is not separate from human beings. In fact, human cultural practices can influence evolution in wildlife. This influence is highly pronounced in cities, where people drastically alter landscapes to meet their own needs.
Human actions can affect wildlife evolution in a number of ways. If people fragment habitat, separated wildlife populations can evolve to be more and more different from each other. If people change certain local conditions, it can pressure organisms in new ways that mean different genes are favored by natural selection and passed on to offspring – another form of evolution that can be driven by what people do.
In a recent review, evolutionary biologists Marta Szulkin, Colin Garroway and I, in collaboration with scientists spread across five continents, explored how cultural processes – including religion, politics and war – shape urban evolution. We reviewed dozens of empirical studies about urban wildlife around the globe. Our work highlights which human cultural practices have and continue to shape the evolutionary trajectory of wild animals and plants.
Religious practices
If you’ve traveled internationally, you may have noticed the menu at any one McDonald’s restaurant is shaped by the local culture of its location. In the United Arab Emirates, McDonald’s serves an entirely halal menu. Vegetarian items are common and no beef is served in Indian McDonald’s. And in the United States, McDonald’s Filet-O-Fish is especially popular during Lent when observant Catholics don’t consume meat on Fridays.
Similarly, ecosystems of cities are shaped by local cultural practices. Because all wildlife are connected to the environment, cultural practices that alter the landscape shape the evolution of urban organisms.
Populations of fire salamanders have different genes depending on which side of city walls in Oviedo, Spain, they live on.
Patrice Skrzynski via Getty Images
For example, in Oviedo, Spain, people constructed walls around religious buildings between the 12th and 16th centuries. This division of the city led to different populations of fire salamanders inside and outside the walls. Because salamanders can’t scale these walls, those on opposite sides became isolated from each other and unable to pass genes back and forth. In a process that scientists call genetic drift, over time salamanders on the two sides became genetically distinct − evidence of the two populations evolving independently.
Imagine dumping out a handful of M&Ms. Just by chance, some colors might be overrepresented and others might be missing. In the same way, genes that are overrepresented on one side of the wall can be in low numbers or missing on the other side. That’s genetic drift.
Introducing non-native wildlife is another way people can alter urban ecosystems…
