The consequences of religion, politics and war extend far beyond human societies. They are also reshaping the evolutionary trajectories of animals and plants in cities around the world. This is according to a groundbreaking analysis from Washington University in St. Louis, which delves into the factors influencing urban life.
Such forces have often been examined through social or historical lenses. Nevertheless, the authors present their arguments in a new review published in Nature Cities. They believe that their impact on urban evolutionary biology has remained largely overlooked.
“For a long time, we have separated humans from biology.” Elizabeth Carlen said this. She is the co-lead author and a Living Earth Collaborative postdoctoral fellow at WashU. “But humans, especially in urban areas, are a very active part of biology, and our decisions have consequences.”
Carlen and colleagues assembled a team of researchers from five continents. Their goal was to understand the impact of religion, politics, and war on evolution. These forces are subtly driving change in urban environments, impacting evolutionary pathways.
RELIGION’S SUBTLE EVOLUTIONARY EFFECTS
Religious practices, the researchers found, often alter species genetics and distributions in unexpected ways. These urban impacts can lead to surprising changes:
- Walled religious structures in Oviedo, Spain, created physical barriers that drove genetic drift in local fire salamander populations.
- The ritual release of prayer animals like birds, fish and bullfrogs, allows human-mediated gene flow. It moves individuals—and their genes—far from their native ranges.
These examples illustrate how culturally driven practices can produce cascading effects on biodiversity.
POLITICS SHAPE URBAN HABITATS
In cities like St. Louis, Carlen’s own research demonstrates that politics, including crime prevention strategies, can indirectly reshape urban evolutionary processes.
“Places like Fountain Park and Fairground Park don’t have any low bushes or small trees. This is partly to enable police to see across the landscape,” Carlen explained. “But if you’re a small animal, moving across that space becomes much more difficult. Raccoons and other wildlife are more exposed.”
Such habitat simplification, common in urban areas, reduces cover and increases predation risks, ultimately influencing which traits and behaviors are favored over time.
WAR LEAVES GENETIC SCARS
Conflict also disrupts ecosystems, displaces species, and introduces new selection pressures, especially in urban zones affected by war. Carlen noted that researchers are increasingly using digital tools, like social media posts, to document wildlife changes during war.
“One of our co-authors published a paper on social media accounts of animal changes during war,” she said. “People post photos of animals trapped or displaced by bombing. We can now study these impacts in real time.”
A CALL FOR NEW RESEARCH
The authors proposed a list of testable hypotheses. Their goal is to spur future studies. They emphasized the need to record environmental and evolutionary impacts as they happen, deeply intertwined with urban challenges.
“Religion, politics and war are all highly interconnected,” Carlen said. “It’s difficult to separate these processes. This separation challenge results in a mess for human societies, biologists, and the wildlife influenced by our actions.”
DESIGNING CITIES FOR PEOPLE AND NATURE
Ultimately, understanding how social processes influence urban evolution can inform better city planning, the researchers argue—designing urban spaces that support both people and the evolutionary potential of species that share our cities. Their work highlights both the urgency—and the potential—for cities to be redesigned in ways that balance human needs with the long-term resilience of urban ecosystems.
