Giving birth to a child is one of the most painful processes a woman can go through in her life. In many instances, it can also be fatal. According to the World Health Organization, about 830 women die each day because of the complications of childbirth and pregnancy. These figures are quite alarming compared to other mammals as they don’t pay such a huge price for giving birth to their offspring. Even though these death rates are dropping, the question of why childbirth is so difficult for humans still exists.
Scientists think that the issue started about 7 million years ago with our primitive ancestors, the hominins. From the fossils of hominins, it was found that they too walked upright. Walking on 2 legs required their skeleton to be restructured, which affected their pelvis. The pelvis of hominins looked very different from the pelvis of primates, which was quite straight. The homonins’ hips were narrow and their birth canal was quite uneven along its length. Their babies could not easily slide through. Instead, they had to twist and turn in order to be born.
The problem did not stop there. About 2 million years ago, hominins underwent more structural changes. They grew taller, their arms became shorter, and their brains increased in size. Bigger brains meant babies had bigger heads now. These changes made childbirth much more difficult than it already was. Since hominin women still required a narrow pelvis to be able to walk efficiently on 2 legs, it became very difficult to push out babies with larger heads. Since then, giving birth has become a painful, possibly fatal, process. This idea of evolution and childbirth was named the obstetrical dilemma by an anthropologist named Sherwood Washburn in 1960.
In the past few years, scientists began to challenge this idea as they feel it is too simple and there are many other factors associated with childbirth. Washburn, in his article on the obstetrical dilemma, said that humans found a solution for this dilemma by shortening the duration of their pregnancy. This is why babies were still small and underdeveloped when born. This idea seemed logical, but in reality, humans pregnancies are long and babies are bigger than expected. Human pregnancies last 38 to 40 weeks, whereas chimpanzee pregnancies last 32 weeks and gorilla and orangutan pregnancies last about 37 weeks. Since human babies’ brains are larger than that of primates, Washburn’s prediction of the obstetric dilemma was deemed incorrect.
Another issue that came up with the obstetrical dilemma was that its main assumption was that women had narrow hips to be able to walk efficiently. If that was the case, evolution would have done its bid to solve the problem of painful childbirth by making women’s hips broader. Anna Warner at Harvard University in Cambridge and her colleagues conducted a research on male and female volunteers who were asked to walk and run in the lab. They found that the size of the hips did not affect their ability to walk or run.
Helen Kurki of the University of Victoria conducted her own research and found more issues with the hypothesis of the obstetrical dilemma. She reported that the size and shape of the birth canal vary quite a bit between women. This variation should have been stabilized by natural selection. Holly Dunsworth of the University of Rhode Island, Kingston, believes that energy is also a very important part of human pregnancy. It takes a lot of energy nourishing an extra human brain. The timing of childbirth is administered by the difficulties that arise when nourishing a fetus beyond 39 weeks of gestation and not by the difficulty of pushing a baby through the birth canal. The size of the pelvis is exactly the size it needs to be. If the size had to be any bigger, evolution would have done it by now, but it has not.
Jonathan Wells, a student of childhood nutrition at University College London, looked at prehistoric childbirth and came to a conclusion that childbirth may not always have been as difficult as it is now. Evidence suggests that for Homo erectus and some Neanderthals, childbirth must have been easier. The number of newborn skeletons was relatively less, suggesting that death rates newborns were low. The number of skeletons of newborns increased a few thousand years ago when people began farming. Wells believed that the developmental changes that occurred when people started farming may have increased the mortality rate during childbirth. The diet of farmers consisted of more carbohydrates and fewer proteins so they had a shorter stature. Shorter women meant narrower hips. Carbohydrate-rich diets also resulted in larger and fatter fetuses. So childbirth, which was relatively easy millions of years ago, suddenly became much more difficult for women.
All the factors such as the size of the pelvis and birth canal, dietary changes, the changing size of the fetus, and the requirement of energy during pregnancy are important in determining why pregnancy is so painful for humans. Some studies suggest that the chance of survival of babies is directly proportional to their size and the size of a newborn is heritable to an extent. These factors might also cause the human fetus to grow beyond the size limit imposed by a woman’s pelvis. Still, a lot more studies need to be conducted on this issue of painful and dangerous childbirth.
