Does Darwin’s “natural selection” work faster?

Darwin’s theory of evolution describes “natural selection” as the successful adaptation of a species as a result of inherited genetic changes over time. While this has traditionally been viewed as a relatively slow process (taking at least several generations to make the change), it seems that we have probably underestimated genetic inheritance rates. An international team of 40 researchers from 27 scientific institutions found that “fuel for evolution” appears to be more abundant than previously thought – and natural selection is happening at two to four times faster.

‘From Darwin, researchers have identified many examples of Darwinian evolution that occurred within a few years,’ says project leader Dr Timothée Bonnet of the Australian National University (Australia).

“A common example of rapid evolution is the peppery moth, which was predominantly white before the industrial revolution in the UK. With pollution leaving black soot on trees and buildings, black moths had a survival advantage because it was harder for birds to spot, “Bonnet continues.” Because the color of the moth determined the likelihood of survival and was due to due to genetic differences, populations in England quickly became dominated by black moths “.

The evolution of the peppered moth (Biston betularia) is a classic example of Darwin’s natural selection, where before the industrial revolution, most morphs were white. Due to pollution, dark morphs have become more common to remain camouflaged. Credit: Ian_Redding / Getty Images

This is the first study to examine the speed of evolution on a large scale, including 19 wild animal populations from around the world. All populations were monitored for long-term periods, ranging from 11 to 63 years, providing data on natural selection of over 249,430 individuals. The superb fairy wrens of Australia, spotted hyenas of Tanzania, singing sparrows of Canada and red deer of Scotland were among the animals followed in this quest. These species cover a wide range of ecologies, life histories and social systems and inhabit diverse terrestrial habitats.

“We needed to know when each individual was born, who they mated with, how many children they had and when they died. Each of these studies lasted an average of 30 years, providing the team with a staggering 2.6 million hours of field data, “says Bonnet.” We combined this with genetic information about each animal studied to estimate the extent of genetic differences in their ability to reproduce in each population “.

After three years of effort, Bonnet and the team have finally quantified the extent of species change due to genetic changes caused by natural selection. They confirmed that the additive genetic variance (measured as VA) that occurs in multiple populations had median and mean values ​​that were two to four times greater than those of previous estimates. This VA also affects relative fitness, the likelihood of reproducing and passing on genetic information.

“The method offers us a way to measure the potential speed of current evolution in response to natural selection in all traits of a population. This is something we haven’t been able to do with previous methods, so being able to see so many potential changes came as a surprise to the team, ”said Dr Bonnet.

While the blue tits (Cyanistes caeruleus) from Italy showed a large amount of additive genetic variance, which resulted in a relatively small change in their relative physical form (6%). Conversely, snow voles (Chionomys nivalis) of Switzerland had lower amounts of VA, but represented a higher percentage of their relative eligibility (30%).

‘This was a remarkable team effort that was made possible because researchers around the world were happy to share their data in a great collaboration,’ says Professor Loeske Kruuk of ANU and the University of Edinbugh (United Kingdom). “It also shows the value of long-term studies with detailed monitoring of animal life histories to help us understand the process of evolution in nature.”

It is still too early to tell whether the actual rate of evolution is happening faster than before, as we don’t have a baseline for comparison. However, with this model we can now begin to measure the amount of genetic “fuel” available and begin to quantify Darwin’s theory of evolution.

Natural selection, evolution, genetic variance
Snow vole Chionomys nivalis, one of the species included in the study. Credit: Per Grunditz / EyeEm / Getty Images

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