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Humans are reshaping nature in ways that go deeper than we realize—right down to the DNA of the plants and animals around us. Evolutionary biologist Menno Schilthuizen has discovered that city-dwelling creatures are rapidly evolving to thrive in a human-dominated world. From birds adapting their songs to higher pitches to cut through traffic noise, to mice in Central Park adjusting their genes to handle fat-laden street food, urban evolution is happening at lightning speed. Even Caribbean lizards are developing traits to better cling to smooth, man-made surfaces! This era in human history is giving rise to a new breed of urban wildlife: quick, clever, and perfectly suited to thrive in the concrete jungle.
Curious about how our animal neighbors are adapting to the urban environment? Click through the gallery to learn more.
City life is rewriting the rules of evolution! In New York City, brown rats might be developing smaller teeth, while tiny fish in the Eastern US have found ways to flourish in heavily polluted waters. Globally, urban environments are driving plants and animals to evolve differently compared to their rural counterparts.
In downtown Toronto, white clover is less likely to produce cyanide—a natural defense against hungry herbivores—compared to its rural counterparts. This fascinating shift, revealed by a new study, shows a similar pattern in cities worldwide, spotlighting how urban conditions even influence the chemistry of plants.
Genetic changes across species reveal how living organisms adapt to bustling city environments. According to Marc Johnson, an evolutionary ecologist at the University of Toronto Mississauga, cities don’t just modify landscapes: they create entirely new ecosystems, driving remarkable evolutionary shifts.
Cities are the planet's fastest-growing ecosystems, housing over half of the global population. It’s no wonder that urban species evolution, a field that was virtually unheard of at the start of the millennium, has now become a hot topic in biology labs worldwide.
Why do some species thrive in cities while others struggle? One hypothesis points to certain traits like learning ability, mobility, and flexibility. These characteristics may give some animals and plants a head start in adapting to urban environments, allowing them to better navigate the challenges of city life.
Jason Munshi-South of Fordham University discovered that two genes in Central Park mice have evolved differently from other urban mouse populations. These genes provide resistance to aflatoxin, a toxic compound produced when certain fungi infect nuts like discarded peanuts—a hazard for many mammals, including humans.
With 25 million visitors annually, Central Park is a haven for more than just humans; its mice are thriving on the junk food left behind. From discarded nuts to muesli bars, these human-derived treats provide a substantial part of their diet.
While fattier than natural foods, some human leftovers may contain aflatoxins, posing unique challenges and driving fascinating genetic adaptations in the park’s rodent population.
Anole lizards, renowned for their incredible diversification into hundreds of species across the Caribbean, typically evolve under natural conditions. Yet, one species in Puerto Rico defies the norm by thriving in both forests and bustling cityscapes.
In their natural forest habitat, this species scurries along branches, hunting insects. However, city life has changed their routine; in urban settings, they are often found clinging to human-made structures like walls and windows, navigating smoother surfaces that are a far cry from the rough textures of tree bark.
Urban life has transformed the anatomy of city-dwelling anole lizards. Their legs have grown longer, and they’ve developed toe pads with more lamellae—specialized structures under their feet—for enhanced grip.
In Los Angeles, bobcats are venturing further into human-dominated areas, adapting well to crossing gardens and streets with ease. However, their urban exploration hits a roadblock with massive highways, which remain insurmountable obstacles.
In Los Angeles, two major highways split the bobcat population into four isolated sections. These highways act as genetic barriers, preventing the animals from easily moving between areas.
Wildlife zoologist Laurel Serieys discovered that this genetic segregation is clearly reflected in the bobcats’ DNA. While bobcats frequently mix within their own section, highway barriers limit their crossing, leading these populations to evolve independently—a striking example of urban infrastructure shaping wildlife genetics.
In the 1980s, some dark-eyed juncos, normally mountain forest breeders, made the bold move to settle year-round in San Diego, California. This shift marked a fascinating change in their behavior, showcasing how city life can influence even the most intimate aspects of wildlife evolution.
Female city-dwelling juncos show a clear preference for males with fewer white tail feathers, while their forest relatives favor mates flaunting plenty of white in their tails.
City life is reshaping both the looks of male dark-eyed juncos and the preferences of their female counterparts: the white in their tails is fading, and the males' head coloration is becoming less striking. These traits, once vital for defending forest territories, seem less critical in urban environments.
Urban ecosystems often rely on species introduced by humans, many of which aren't native to the area. Surprisingly, these non-native species frequently play a key role in maintaining the balance and functionality of city environments, proving that the best fit for urban life isn’t always the local wildlife.
To make cities greener, the ideal candidates are species already acclimated to urban conditions, not just those chosen from garden center catalogs. Plants that have spent years adapting to city environments, like those thriving in vacant lots, are better suited for urban ecosystems and more likely to thrive in the concrete jungle.
While some species excel at adapting to city life, this doesn’t diminish the pressing need to protect Earth's untouched natural spaces. Schilthuizen highlights the fascinating evolutionary changes in artificial urban ecosystems, but warns of the tragedy of losing species that depend on pristine habitats for survival.
Only a handful of species have managed to evolve and adapt to the artificial conditions of urban environments. Their success often comes down to sheer luck—possessing the right genetic variants to endure the changes we've imposed.
While we celebrate the few that thrive, countless others silently vanish, unable to cope with the drastic changes we've imposed on their environments. Their disappearance serves as a stark reminder of the limitations of nature's adaptability in the face of human interference.
To safeguard the majority of Earth’s biodiversity, protecting untouched natural areas remains essential. At the same time, there’s much to marvel at in the evolutionary changes occurring within the artificial ecosystems of cities—where nature finds surprising ways to adapt and thrive alongside humans.
As one potential solution, Schilthuizen envisions an "Urban Evo Scope," a citizen science project where city residents observe and document the appearances of urban wildlife, particularly through all kinds of photography.
In Holland, a pilot project is paving the way for mapping urban evolution through citizen science. Participants are photographing a unique land snail species, the grove snail, known for its variety of shell colors.
Collected evidence suggests that grove snail shells are evolving lighter colors in cities compared to rural areas. This adaptation appears to combat the urban heat island effect; lighter shell colors help reflect heat, offering the snails protection against overheating.
Citizen scientists have already uploaded nearly 10,000 grove snail photographs to a dedicated website. Currently, human validators are needed to review these images, but with advancements in artificial intelligence, automated image analysis and recognition could soon take over.
Schilthuizen imagines a groundbreaking automatic monitoring system for urban evolution, powered by public participation. This system would enable ordinary citizens to continuously observe evolutionary processes or even uncover unexpected examples of species adapting to urban life.
This initiative offers the general public an engaging way to grasp the process of evolution. By observing and documenting the changes in urban species, people can begin to appreciate that evolution isn’t just an abstract concept—it’s a phenomenon they can witness firsthand, even in their own backyard!
Sources: (CNN) (Knowable Magazine) (E360) (Phys.org)
See also: How scientists are bringing animals back from extinction
How do animals and plants survive and thrive in cities?
Urban Darwinism in action
LIFESTYLE Wildlife
Humans are reshaping nature in ways that go deeper than we realize—right down to the DNA of the plants and animals around us. Evolutionary biologist Menno Schilthuizen has discovered that city-dwelling creatures are rapidly evolving to thrive in a human-dominated world. From birds adapting their songs to higher pitches to cut through traffic noise, to mice in Central Park adjusting their genes to handle fat-laden street food, urban evolution is happening at lightning speed. Even Caribbean lizards are developing traits to better cling to smooth, man-made surfaces! This era in human history is giving rise to a new breed of urban wildlife: quick, clever, and perfectly suited to thrive in the concrete jungle.
Curious about how our animal neighbors are adapting to the urban environment? Click through the gallery to learn more.