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The downstream consequences of religion, politics and war can have far-reaching effects on the environment and on the evolutionary processes affecting urban organisms, according to a new analysis from Washington University in St. Louis.

Typically viewed from a sociological perspective, the implications of religion, politics and war are rarely discussed in the field of evolutionary biology. That should change, according to an international team of biologists, including Elizabeth Carlen in Arts & Sciences at WashU, co-lead author of a review published in .

Better understanding the effects of religion, politics and war on urban evolutionary biology can enhance our ability to design and remodel cities to make them better for people while supporting the environment and evolutionary potential within the city, the study authors said.

"For a long time we have separated humans from biology. But humans, especially in urban areas, are a very active part of biology, and our decisions have consequences," said Carlen, a Living Earth Collaborative postdoctoral fellow.

She helped organize a team of contributors from five of the seven continents of the world to offer global and local perspectives on the social processes discussed in the paper.

Starting with religious practices, the authors described ways that socially driven interactions between humans and urban wildlife can lead to evolutionary change for animals or plants. While previous research has established that religious practices have shaped urban biodiversity, the study authors argue that such practices also generate downstream evolutionary change in urban wildlife.

In one example, when walls were constructed around religious buildings in the city of Oviedo, Spain, that change led to genetic drift and resulted in population differences among fire salamanders (Salamandra salamandra) within and outside the walled area.

In another religion-related example, the ritual release of prayer animals—the paper mentions birds, fish and even bullfrogs—in cities often involves the capture and release of wild animals; this release may occur far from where the animal was captured, leading to human-facilitated gene flow.

The study authors offer a list of testable hypotheses for future research furthering our understanding of the impact of religion, politics and war on urban evolutionary biology. They also encouraged scientists to think about how they could record changes as they are happening.

"Digital technology has allowed us to revolutionize what kind of data we're collecting," Carlen said.

"One of our co-authors published a paper on social media accounts of animal changes during war," she said. "So, for example, going through Twitter and Instagram and finding posts that people had put up showing a polecat that's stuck in the crater of a bomb. We now have that capability to document things like that, even though a war is going on."

In her own work in the American Midwest, where Carlen is studying the impacts of environmental management decisions on wildlife, including Eastern gray squirrels, politics can exert a sizable influence on biodiversity and evolution, she said.

In St. Louis, political mandates have led to a crime prevention approach in certain areas of the city that can have an impact on biodiversity, Carlen said. "Places like Fountain Park and Fairground Park don't have any low bushes and don't have any small trees. This is partly because it enables police to see across the landscape.

"But you can imagine, if you're a small animal, moving across that same space becomes much more difficult," she said. "Raccoons moving across an open space are more vulnerable than if there's a bush that provides cover."

The biologists emphasized the need for additional research to tease apart how evolution is being shaped by human conflict and socially driven choices.

"Religion, politics and war are all highly interconnected," Carlen said. "It's difficult to separate these processes in many instances, making things messy for human societies, biologists and the wildlife being influenced by our human actions."