Animals living in cities are adapting faster than humans in the evolutionary race for survival – RN
Puerto Rican anole lizards have evolved so their feet can better grip city surfaces. (Wikimedia Commons)
We might think city-dwelling humans and wildlife are competing in a hopeless game of “survival of the fittest” — where the animals just don’t stand a chance.
But that’s where we — and even Charles Darwin — may be wrong. Animals, with the help of evolutionary biology, might just out-adapt us all.
Take for example, the anole lizards in Puerto Rico, whose feet are evolving to better grip city surfaces like concrete. Human feet, on the other hand, have not evolved such abilities.
Evolution ‘much faster’ than Darwin thought
We tend to view evolution as an achingly slow process, spanning hundreds, even thousands of years and that’s what Darwin posited all those years ago in On the Origin of Species.
But evolutionary biologist Dr Menno Schilthuizen, author of a new book Darwin Comes to Town: How the Urban Jungle Drives Evolution, thinks Darwin may have been surprised by what is happening in cities.
“The process that causes the urban animals and plants to evolve, of course is the same process that he [Darwin] uncovered,” Dr Schilthuizen says.
“But at the same time we see in cities and other manmade environments that evolution really proceeds much faster than Darwin himself thought, at that time.”
But how fast is the evolutionary clock ticking?
Dr Schilthuizen cites the mummichog, a small brackish water fish from the east coast of North America, as an indicator of the pace of adaptation to environmental changes.
“The mummichog lives in estuaries and ports and areas that sometimes are very heavily polluted by PCB’s (Polychlorinated Biphenyls), which are chemical compounds that are lethal to most fish and probably also these mummichog fish,” Dr Schilthuizen explains.
“Now mummichog populations living in these very polluted ports are able to withstand levels of PCB’s that are thousands of times higher than they normally would be able to survive.”
“And this has happened in a space of about 10-15 years.”
The only way to survive, for some
The generational changes of the mummichog and other species are even more telling.
“We do see that the shorter the generation time of animals or plants, the faster they can evolve,” Dr Schilthuizen says.
“This is sort of like evolutionary clock speed, because [with] every generation you see the effect of natural selection in the previous generation. So the shorter that time period, the faster these changes can take place.”
For some species like the mummichog, evolution and adaptation are the only way to survive.
These transformations are not just happening to sea creatures: those that live on land and in the air are learning to adjust to city life.
The European blackbird was one of the first species to colonise cities.
“They have gone quite far in their evolution, including the shape of their beaks, which are shorter in cities,” Dr Schilthuizen says.
“But they’ve also changed the pitch of their song, they don’t migrate anymore and their digestive system has changed.”
Formation of a new species
The acceleration of the evolutionary process may be the start of an entirely new species.
The European blackbird has adapted its biology to the city environment. (Getty: Christine Rose)
“The blackbird is an example of a species that has adapted to the city environment in many different aspects of its biology, so probably in many separate genes on the chromosomes. Then you can say, it’s really beginning to split into two,” Dr Schilthuizen says.
The difference in migratory pattern between forest blackbirds and urban blackbirds is quite striking. Urban birds opt to stay in the city for warmth and easier access to food. They also start breeding earlier than the forest dwellers.
This can lead to a reproductive knock-on effect. “There’s not much genetic exchange anymore between the forest and the urban blackbirds. Which is a hallmark of the formation of new species.”
A blood-sucking example from far below a city’s surface is the London Underground mosquito.
Mosquitos in the London Underground have developed line-specific differences. (ABC News: Kathleen Dyett)
“[London Underground mosquitoes] don’t mate in these big clouds anymore where you have mixtures of males and females that are mating with each other. They really mate one-on-one in some small confined spaces.
“They also don’t need a blood meal anymore before they can lay eggs.”
Rail line specific blood suckers
Remarkably, the mosquitoes living in the London Underground are also line-specific.
“They have these separate subway lines which are basically a separate environment so the mosquitoes in the Victoria line don’t mix with the mosquitoes in the Bakerloo line,” says Dr Schilthuizen.
“And you see that even within these separate areas underground, you see that there are differences evolving. They’re not separate species in different lines, but you have some sort of different variations of that new underground mosquito there.”
There are more examples of fauna acclimatising to an urban existence.
If you find yourself in Chicago, be prepared to see urban coyotes raising their young on rooftops and looking both ways as they nonchalantly cross Michigan Avenue.
Humans may eventually change too
In New York’s most famous park, the mice have found a way to stay lithe.
“In Central Park, the mice have genes which protect them against dealing with very fatty foods, because there’s a lot of junk food of course being thrown away,” Dr Schilthuizen says.
“But because of generations of natural selection they’ve adapted to being able to deal with that human food.”
Mice in New York’s Central Park have developed genes to cope with human food. (Getty: Alan Tunnicliffe)
The only species not adapting to urban life is humans. We have not evolved into city-specific beings… “Yet,” says Dr Schilthuizen.
“Fortunately we don’t die by the numbers that animals and plants die, so this natural selection is not so strong in us.
“But you could still expect that probably over thousands of years if we continue this living in cities, we are going to see some change.”