How is human evolution changing?
Human evolution goes on happily
British wildlife filmmaker and naturalist David Attenborough sparked some discussion almost six years ago. In a radio interview he said in a general sense: The evolution of humans has ended because we are the only living beings on earth able to raise 95 to 99 percent of the offspring without falling victim to natural selection.
So have we overcome evolution because we have been able to greatly reduce child mortality in numerous countries (in African and Asian countries, however, it is still far from at a desirable level)? This opinion is fairly widespread. Even before Attenborough's statement, humans, as they are currently genetically endowed, were seen as an evolutionary masterpiece, as the final climax of development. Millions of years after we split off from the ape, that should have been it. We can walk upright, so please, what's next?
Small development steps within a few years
First of all: evolution takes place and cannot be stopped. This is confirmed by numerous evolutionary biologists such as Philipp Mitteröcker from the University of Vienna. Sometimes two to three decades would be enough, he says, "as an evolutionary biologist you don't necessarily have to calculate in steps of several million years." Evolution mainly takes place because there are genetic and phenotypic differences that have to do with reproductive success. "And it will stay that way in the long term," says Mitteröcker.
The scientist cites an example about which he has published several articles in the specialist journal in recent years PNAS could publish. This is an evolutionary dilemma. Actually, the birth duct of women should be wider than before in order to enable the safe delivery of the offspring. The pelvic head mismatch - the baby's head is larger than the birth canal - is therefore relatively common. On the other hand, it is probably a good thing that the canal is not too wide, because otherwise it would lead to prolapsed uterus and incontinence. The woman's pelvis must create stability.
Selection pressures due to malaria
However, the medical solution to the dilemma, the caesarean section, has eliminated the corresponding evolutionary compromise and apparently intensified the dilemma: In a study, a team led by Mitteröcker was able to show that women who were born by caesarean section develop a skull-pelvic disproportion more often than women born without surgery.
Mitteröcker mentions another example of human evolution in the present. In Africa there is massive selection pressure due to malaria. A mutated hemoglobin gene that protects against infections caused by the dangerous mala fever has therefore spread. But if people have two hemoglobin genes instead of just one, sickle cell anemia develops, which leads to blockage of blood vessels. The selection pressure has therefore led to the Beelzebub being used to drive out the devil. It can be shown that the frequency of the mutated hemoglobin gene is an evolutionary "compromise" between these two evils, according to Mitteröcker.
Another well-known example is mentioned by the British evolutionary biologist Nicholas Barton from IST Austria in Maria Gugging near Vienna: lactose intolerance, which leads to digestive problems after consuming dairy products. That is actually the normal state and not a disease, but humans have developed the tolerance of dairy products in western countries through the triumphant advance of agriculture and cattle breeding. The selection pressure made it possible because humans could survive even better with it than without. In many countries, however, intolerance still persists - in South Africa, for example, or in China. In the Middle Kingdom people are now trying to outsmart evolution. In Beijing there are now milk bars that are very popular - but at the cash desk, every customer is offered a drug that prevents the unpleasant consequences of lactose intolerance on the metabolism.
What does the future hold? Barton says that evolution has no plans, it is an unpredictable and also uncontrollable process. At present it is also influenced by socio-cultural developments, such as modern medicine. For example, a hundred years ago diabetes was a disease with which there was hardly any chance of survival. Today, with new drugs, artificial insulin and flexible sugar management, you have a normal life expectancy, but you can also pass on the potential for the disease to your offspring.
Influence of modern medicine
Mitteröcker believes that one must be aware of this development, that modern medicine is also changing evolutionary processes. With this knowledge, medical and social structures can be better adapted to human biology. The eugenics developed in Great Britain about 150 years ago, which reached its terrible climax in the racial theories of National Socialism, wanted the opposite: the human biology should be adapted to social norms and ideals.
Barton and Mitteröcker warn against using technologies to intervene in evolution. In principle, it is to be welcomed to be able to eliminate diseases through genome editing in general and the CRISPR / Cas9 gene scissors in particular. But that is just a dream of the future. "We only know about most genes that they play a role in a certain disease, but not what roles they still have or how they interact with other genes."
Enter the charlatan
The possibilities that genome editing offers could of course be used by charlatans by intervening in the germ line. He Jiankui, now laid off at the Southern University of Science and Technology, made negative headlines because he had allegedly genetically modified unborn twins to make them resistant to the HIV virus.
Science as the mistress of evolution? For ethical reasons, manipulation of the embryo should be rejected, say experts. Also in the interests of the unborn children, who may even experience other disadvantages that they would otherwise not have. (Peter Illetschko, February 10, 2019)
Everything you need to know about the future can now be found in our new section, Edition Future: derStandard.at/Zukunft
The work of the Barton Group at IST Austria: here
Paper by Philipp Mitteröcker:here
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