How does our lifestyle affect human evolution
Human evolution continues
Philipp Mitteröcker from the University of Vienna thinks the achievements of modern medicine are fundamentally great. "We want to escape natural selection as much as possible," says the anthropologist and evolutionary biologist. But that does not mean that evolution stops. Rather, it is so that the balance of different selection pressures shifts. "It's a complex thing," says Mitteröcker. Often a certain quality is good for one function, but bad for another. So it is beneficial to have a strong immune system to be able to kill pathogens. On the other hand, too strong a defense can lead to autoimmune diseases.
Evolution works like a hobbyist in his shed
How much culture and evolution interact and even change our physique is shown by an example that Mitteröcker himself has researched intensively: the human pelvis. As a woman, having a wide birth canal is helpful in having children easily. Especially since larger newborns generally have a greater chance of survival. On the other hand, women with a wide pelvis are more likely to struggle with incontinence or a sagging uterus. So the selection pressure towards the big child is opposed to that towards the narrow pelvis. Over time, a balance has emerged, a kind of evolutionary compromise: the pelvis is wide enough for childbirth, but narrow enough for most women to stay healthy.
However, in the middle of the 20th century this balance shifted. The reason: Caesarean sections were introduced. Since then, women with a pelvis that are too narrow have also been able to give birth without any problems. With the help of a mathematical model, Mitteröcker's team calculated that since then the birth canal and the newborn are much more often disproportionate. According to the study, the incidence has increased by 10 to 20 percent. And it will continue to grow, because women who were born by caesarean section for this reason are then more often dependent on delivery by caesarean section - two to three times as often as women who were born naturally.
But there are not only anatomical reasons for a caesarean section. "There is a very complex network of environmental, biological and sociocultural factors that come together," says Mitteröcker. After all, very few women today are able to give birth to a child completely without help. So obstetrics itself is a cultural factor that has influenced our evolution.
A similar "cultural" phenomenon could be behind the fall of the additional artery. Perhaps people born with the artery had a slight infection in the womb that interrupted the normal regression process, the study's authors speculate. The fact that the once rare artery has spread so amazingly quickly can then be explained by the fact that, thanks to modern medicine, problem pregnancies lead to a successful birth much more frequently than in the past.
Our bodies are set up to hunt and gather. What we do: sit
It would also be conceivable that the selection pressure has relaxed, which counteracts the retention of the additional vessel. Those who have to hunt every day or work their fields cannot afford carpal tunnel syndrome. Today, however, it is only uncomfortable and painful; but it can be treated well and in the rarest of cases threatens the existence.
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