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A new study has discovered a powerful force that is now driving evolution on Earth.

Evidence is mounting that humans are now a major driving force in Earth's evolution. We're changing so much of our world, from selective breeding to environmental alterations, that we're no longer just controlling the climate, but the path of life itself.


Researchers explored how urbanisation has altered evolution on a worldwide scale in a huge experiment comprising 287 experts from 160 locations in 26 nations. White clover (Trifolium repens) was utilised as a model - a plant native to Europe and western Asia that is now widespread in cities all over the world.

There has never been a global study of how urbanisation effects evolution or a large-scale field study of evolution.

They found that clover in cities is now more comparable to clover in another city a globe away than it is to clover in neighbouring farms or forests, independent of climate, after collecting more than 110,000 samples along gradients extending from cities, through suburbs, and out to the country.

This is an example of parallel adaptive evolution, which occurs when various populations in different regions are influenced by the same selective pressure for certain traits. It demonstrates that human-caused environmental change has a greater impact on these qualities than natural factors such as local population genetics and climate.

While urbanisation has a lot of characteristics in common over the world, it wasn't clear that they were all working together to push evolution in the same direction.

Urban regions must converge in environmental factors that affect an organism's fitness for parallel evolution to occur.

The multinational team discovered that the plant's generation of hydrogen cyanide was one of the properties that changed along urban-rural divides. This molecule is used by white clover as a defensive mechanism against herbivorous animals. It also aids with drought resistance.

Plants in the most remote rural areas were 44 percent more likely to produce hydrogen cyanide than those in urban areas. In rural locations, grazing pressure appears to favour the creation of more hydrogen cyanide than in cities, where grazing pressure isn't as intense; in the absence of this pressure, drought appears to be the driving force.

Despite high gene flow across white clover populations throughout each gradient, this means that the amounts of this chemical are being severely chosen for time after time.

We've already shattered the ocean's natural size spectrum, in part by choosing culling giant fish through fishing, leaving more fish with small fish DNA to form future generations. Many fish have shrunk by 20% and their lifecycles have shrunk by 25% on average.

Birds' shapes are altering as a result of our actions' unforeseen repercussions.

Cliff swallows' wing span has evolved to be shorter near roads, with roadkilled swallows' wings being longer, consistent with selection for better agility in traffic.

These new findings provide another another example of an evolving urban signal. According to studies, rates of evolutionary change in urbanising landscapes are higher than in natural and nonurban human systems.

This is the most convincing proof that we are influencing the evolution of life in [cities]. This will be significant for society beyond ecologists and evolutionary biologists. Especially since, by 2030, we're predicted to have tripled the quantity of urbanised land compared to 2000.

The researchers now have a big database on which to look for human influences on clover evolution. We have a better chance of taking the wheel and steering evolution in a more informed and safe manner if we better understand how we're unintentionally fueling such developments.

This knowledge could aid in the conservation of some of the world's most endangered species, the mitigation of pest impacts, the improvement of human well-being, and the understanding of fundamental eco-evolutionary processes.


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