How slow is the evolutionary process

Charles Darwin would be amazed. The founder of the theory of evolution was convinced that the interaction of mutation and selection is a slow process that lasts for millennia or even millions of years. Evolution can also take place quickly, as is now another study by British scientists in the specialist journal Biology Letters (online) shows.

Oxford University researchers analyzed the genome in the mitochondria of a group of chickens that all have the same common ancestors. To their surprise, they found that two mutations had occurred there in the past 50 years. "Until now it was considered certain that the mitochondrial genome would change by a maximum of two percent in a million years," the researchers write. Their discovery shows that it is 15 times as fast.

Those who are perfectly adapted to their surroundings no longer change externally

"It is wrong to assume that evolution is a slow process," says Manfred Milinski, Director at the Max Planck Institute for Evolutionary Biology in Plön. Most species hardly changed because their properties are already at their best. In this case there is a stabilizing selection and therefore no differences can be seen. One example is the human eye. It is so perfect that every change means deterioration and therefore cannot prevail. But as soon as living things have to adapt to new conditions, they often develop surprisingly quickly.

There are many examples of this, and it is often humans who, directly or indirectly, exert high selective pressure on other living beings by changing their living conditions. In Canadian bighorn sheep, for example, the size of the horns shrank by a fifth within a few decades because trophy hunters preferred to shoot animals with magnificent horns. This gave poorer sheep a survival advantage and multiplied. Selection pressure was also exerted by those people who brought the brown Bahamian anole lizard to Florida, where the green red throat anole already lived. Both species are actually found on the lower, broad branches of trees. But space there became scarce over time. The native species therefore opted for higher, thinner branches. In order not to fall off, the animals developed larger, sticky feet in just 15 years.

But even without human influence, evolution can very quickly lead to changes. Manfred Milinski has examined three-spined sticklebacks in Holstein Switzerland, which live there in both rivers and lakes. Outwardly, the fish do not differ. But when the evolutionary biologist examined the immune system of the animals, he found great differences between lake and river inhabitants. The immune system of the animals that originally lived in the sea adapted to the various parasites in lakes and rivers after the fish migrated there from the Baltic Sea, says Milinski. All of this must have happened in the past 4000 years, as the lakes and rivers of Holstein Switzerland were previously not a suitable habitat for the fish.