Why is the world imperfect

Back pain, dangerous childbirth and too many teeth: humans are anything but perfect. This is due to his animal heritage. And the renovation continues. A visit to the body construction site.

scars of evolution

Back pain, dangerous childbirth and too many teeth: humans are anything but perfect. This is due to his animal heritage. And the renovation continues. A visit to the body construction site.

by andrea Eppner

It is an act of strength, painful and often lasts more than ten hours. Above all, however, the birth of a child is risky for the mother: According to estimates, more than half a million women worldwide die every year. “No other species is in as great danger as humans when giving birth to offspring,” says Prof. Karen Rosenberg, anthropologist at the University of Delaware.

The human body is to blame for the risky birth. The child's large head and broad shoulders can only be pressed through the extremely narrow birth canal with great difficulty - by no means the only weak point in the body. The same applies to the back, feet and jaw. An engineer would come to a harsh judgment about people: "What a faulty design!"

If he were given the task of correcting these problems - we would probably not recognize ourselves. But just replace a few parts? Unfortunately, that's not how it works in nature. Instead of building from scratch, it is constantly being renovated and redesigned, driven by the forces of evolution. Only innovations that make it possible for a living being to have more offspring have a chance. It is not uncommon for an advantage in one place to be bought at the price of disadvantages in another. "Evolution produces function, not perfection," explains Prof. Allan Mann, an anthropologist at Princeton University. So man is a compromise.

It is true that he has subjugated the earth with his intelligence. But this is bought at a high price. As the brain grew, so did the skull. The risky birth, which can cost the life not only of the mother but also of the child, is a consequence of this development. Another is less dramatic, but can become annoying and painful: Problems with the back molars, the so-called wisdom teeth. They too are a legacy of our ancestors, a “scar of evolution”, as researchers also call it. Our ancestors not only had bigger and stronger teeth. There was also room for 32 of them in her long jaw. But while the top of the skull grew and even arched forward a little to give the brain more space, the face - and with it the jaw as well - contracted. The rearmost teeth soon had hardly any space.

The blueprint for the unnecessary walkers is still in people's genes. The result: the excess teeth often grow crooked, sometimes even horizontally or cannot erupt properly. "That can lead to chronic pain," explains Mann. “But in general you don't die from it.” When there was no dentist, you had to live with it.

Evidently the evolution of this problem has already taken on. According to Allan Mann, one in four people in many sections of the population has to worry less with a wisdom tooth. In the case of Europeans, it is at least ten to 15 percent. And the anthropologist also has an explanation for this: the complaints could have had an effect on the desire to reproduce - and thus also on the number of children. Over many generations, the proportion of people with fewer wisdom teeth could have increased.

There is another problem that people will have to grapple with forever: the consequences of walking upright. This causes difficulties because the skeleton of our ancestors is still in our bones. But it was built to walk on four feet. In order to be able to walk on two legs, it had to be rebuilt properly. The long and shallow basin became shorter and cupped. It had to help hold the organs of the abdomen - at the cost of a difficult birth. In order to be able to keep the balance on two legs, but still have enough space for the birth, the typical S-shape of the spine was created.

But that also made her extremely prone to back problems. The spine was originally adapted to the needs of quadrupeds. Turning it into a biped created a myriad of problems unique to our species, says Bruce Latimer, professor of anthropology and anatomy at Case Western Reserve University in Cleveland. These include, for example, the herniated disc and scoliosis, a curvature of the spine.

Both diseases are by no means the only consequence of a modern sedentary lifestyle. The cross with the cross is also due to our development history. As Latimer found out, "Lucy" was already suffering from scoliosis. Scientists found parts of her skeleton in Ethiopia in 1974. It is said to be around 3.5 million years old and belongs to the species Australopithecus afarensis, probably an early ancestor of humans.

Admittedly, young people also have back problems. However, these increase with age. Because then the evolutionary design flaws become really noticeable. Because natural selection almost only affects people in their fertile years. Only then can an ailment reduce the number of children. In this way, the characteristics of other, less susceptible people will prevail in the long run. Whether someone turns 100 instead of just 60 usually no longer plays a role in the number of offspring. Likewise, whether painful wear and tear on the hip and knee joints will make walking impossible at some point.

After all: the large brain not only gives people a difficult birth. It also helps him to overcome some “scars of evolution”: For example, modern medicine allows broken joints to be replaced with artificial ones. If the child lies unfavorably in the womb, a saving caesarean section helps. And even when such interventions were still unthinkable, people already managed to reduce the risk of childbearing enormously - by helping her. Animal mothers usually give birth to their young alone.

It was the brain that separated human development so far from that of animals. According to evolution, its volume grew rapidly, from about one liter for the first representatives of the genus Homo to 1.6 liters for Homo sapiens, modern humans. The big brain has not only given us spears, drills and tractors. It also takes far more energy than that of other mammals. But since there was a lack of food for thousands of years, the metabolism has adapted to it. Humans have also become so tricky at finding food that the evolutionary advantage threatens to turn into a disadvantage. "It seems that our nutritional strategies have become too successful," says Prof. William R. Leonard, an anthropologist at Northwestern University in Illinois. “We have become so efficient at generating energy with minimal effort that we have created an ever greater positive energy balance.” In other words: The large brain not only makes us the “crown of creation” - it can also make us quite fat .