The fact that the pregnancy period is 9 months and the babies come into the world in need of care has been explained by the “obstetric dilemma”, that is, the conflict between large brains and narrow birth canals.
Horses can walk shortly after birth, kittens of a few weeks old can remain alone while their mothers search for food, while babies can live for many years. need for care is in a state.
The fact that birth occurs after 9 months and that the newborn human brain is relatively less developed compared to other primate species has caused some problems to date. to evolutionary processes was based. However, a study presented results that suggest the opposite. Do you think the years-old hypothesis will be refuted overnight?
Our evolution process from four legs to two legs
The skeletons of our ancestors evolved over millions of years from a creature that walked on four legs and had a smaller head. Getting into an upright bipedal position, Supports a wide head also means. In fact, this is one of the disadvantages of walking on two legs. Other negative effects may include back and neck pain as the viewing angle expands.
Women experienced the biggest disadvantage of the skeleton supporting a large head. Upright stance, more narrow hips It meant. This was an important physical feature that narrowed the birth canal. Women who gave birth prematurely, when their skull and brain were smaller, survived. On the one hand, this is actually natural selection created. People whose vital systems were not yet fully developed became people born prematurely.
If there was no evolution and humans were born neurologically like chimpanzees, pregnancy would be at least twice as long. This is the pregnancy process 18 to 21 months It would be an extractive process.
Babies’ brains are developed enough to enter the birth canal.
The larger size of women’s pelvises could prevent them from walking. According to the prevailing belief, babies’ brains only grow large enough to fit into the birth canal. That’s why it’s not 18 months birth in 9 months takes place.
When babies are born, their brains are less than 30% of an adult brain. This way, they can pass through the narrow channel. This situation, which is one of the reasons for needing care, begins to return to normal after leaving the womb. Brain development continues after birth and At the end of a year, it will double on average.
A study may challenge this process that has come to this day.
Holly M. Dunsworth from the University of Rhode Island and her colleagues tested the “obstetric dilemma” hypothesis and brought a completely different perspective to the event. According to the hypothesis, the female pelvis being wider than the male’s makes it difficult to perform activities such as walking and running. more energy than men that it requires. In their research article, they stated that a wider pelvis did not cause such a situation.
Dunsworth also noted that for the human brain to reach chimpanzee levels (40% of the human brain’s adult size), the size of the pelvis only increases. Expansion up to 3 cm He also stated that it was necessary. This is actually considered within the normal pelvic range of today’s women. As mentioned, it also refutes the hypothesis that women should spend more energy.
Babies are born when their mothers reach their metabolic capacity.
Dunsworth and his colleagues also answered why babies are born at nine months from another angle. Dunsworth, women’s metabolic capacity He said that there is a capacity and when this capacity is full, babies are born.
In order to continue their normal processes in the first six months of pregnancy, women twice the energy They spend energy, and this energy increases as the baby grows. The fact that the maximum metabolic rate is between 2 and 2.5 times means that women will not be able to convert energy after nine months.
Although this research, which claims the opposite of the obstetric dilemma that has been around for many years, cannot eliminate the entire hypothesis, researchers still think that these arguments will be valid after a while.
Can Babies Feel Stuck in Pregnancy Where the Abdomen Grows Very Little?
The Technology That Gives the First Hints That There Will Be No Such Thing as Pregnancy in the Future: Artificial Wombs