Is childbirth so painful an evolutionary bug?

Regarding evolution, I often see netizens discussing all kinds of questions, such as "Humans have evolved for hundreds of millions of years, why haven't we evolved to reduce the pain of childbirth?" This is indeed a problem, and I want to talk to you about this issue today.

Why is childbirth painful? Essentially, it is because the baby and the pelvis are not adapted. In layman's terms, the squeezing of the baby's head on the pregnant woman's birth canal is the main factor causing childbirth pain. So here comes the question, if you are a God-like designer, how would you design it?

01. From the baby’s perspective

If we consider the problem from the perspective of the baby, reducing the size of the baby's head will only lead to two consequences: premature death and intellectual disability.

1. Premature death. As a mature primate species, our development takes time. A pregnancy lasts for ten months, and it is not like some people think that a child is formed quickly after fertilization and then grows up.

In fact, development means that many organs appear from scratch. Moreover, this appearance cannot be synchronous. Because you need to have a basic idea. Starting from a fertilized egg cell, 2-4-8 all the way to the blastocyst stage.

Next, the embryo begins to fold and form naturally, and then our organs begin to take shape. For example, the nervous system appears first, then the heart, followed by the limbs, hearing, eyes, etc., and things like teeth come later. There is a very important point here: don't expect a cell to be very powerful, and don't expect genes to have much memory, because they will be erased during embryonic reprogramming.

Therefore, the development here must be a natural process. For example, as more cells appear, they are divided into inside and outside, left and right, up and down. Under the influence of very basic natural laws such as gravity and chemical concentration gradient, they begin to activate some genes, and then when these genes develop to a certain extent, they further activate more genes. This is development.

And all of this takes time! Therefore, a person's development takes time. If you terminate this process prematurely, you will face organ deficiency, and thus premature birth and death.

2. Lack of intelligence. If the size is reduced, there is another problem, that is, our brain capacity will decrease, which is not a small problem.

Don't underestimate the human species. In our known geological history, there has never been such a powerful species that has shaped and changed the earth, and even exceeded the boundaries of known organisms. Therefore, humans have reached the pinnacle of species, and even the international geographical community has specially divided geological history into a new period: Anthropocene. And the core of all this change is our brain.

This is not a step-by-step evolution, but a mutation. About a million years ago, the long-term core code of our ancient ancestors was suddenly "iterated" in a short period of time. This iteration is called the "Human Acceleration Region" (HARs).

For example, Nature previously published a study by the University of California, which compared the 49 most different parts of the human genome and the chimpanzee genome and found that a small part had undergone rapid changes, namely the HAR1F gene. This gene has appeared in vertebrates for 300 million years, and the differences are basically very small. For example, the HAR1F gene of chimpanzees and chickens has only two differences, but a million years ago, it suddenly started to soar, and the speed of evolution was like a wild horse. Just a few million years ago, the HAR1F gene in the human genome evolved about 70 times faster than other genes.

The result of this change is that the human brain capacity began to expand rapidly, reaching more than three times the brain of other primates.

Of course, research on HAR is not just focused on a single gene, but also on the role of biological folding, enhancers, etc. For example, this study in Science showed that the accelerated evolution of human genes has led to topological changes and brought about the rapid evolution of neural cells.

When is the HAR1F gene expressed? It is formed between 7 and 19 weeks after pregnancy, which is also the critical period for the development of the human brain embryo.

So, are you willing to sacrifice the intelligence of the human species to reduce the pain of childbirth? If you think changing the baby is too uneconomical, how about changing the pregnant woman? Alas, every cause has its effect, because the birth canal of a pregnant woman is designed to walk upright.

02. From the perspective of pregnant women

The fundamental reason why the human pelvis is like this is because we walk upright. In fact, if you observe animals that do not walk upright, not to mention cattle and sheep, even gorillas and the like, there is no problem. However, when it comes to humans, it is not the same, and the fundamental reason is: walking upright.

The principle is not difficult to understand: a simple gravity structure. When we walk upright, the weight of our entire body is placed on the pelvis, the basic structure.

In the past, the pelvis was only responsible for horizontal movement. But sorry, as we walk upright, the weight of our whole body is pressed down, and our pelvis needs to bear greater gravity and pressure.

The pelvis has to bear the weight of the upper body and also needs to bear the rebound reaction force from the ground, so it requires high stability. Therefore, we must change the pelvic structure to make it flatter and squeeze the birth canal.

However, are you willing to give up walking upright? Don't rush to give an answer, think about the significance of walking upright.

1. Free your hands. I remember a classic saying: The biggest difference between humans and other animals is the use and manufacture of tools. Of course, this has been broken through to a certain extent now, after all, some primates can also use tools, but for humans who have gone through the long Paleolithic Age, entered the Neolithic Age and even today, it is completely different.

Of course, the purpose of freeing hands may not have been to make tools, but to fight. Just like there is a joke to describe humans in the eyes of animals, they can't imagine that during fighting, people's upper limbs become longer (using tools), or, even more outrageous, people's hands fly out and slap themselves (throwing tools).

2. Safer vision. Walking upright may not have been for the purpose of freeing up hands and tools in the early days, but for a very intuitive factor: a better vision.

Coming down from the trees, due to climate change in East Africa, there are fewer trees and the ground is covered with grass. In this case, humans must stand up hard to maintain vision and avoid animals hiding in the grass. This is also an objective natural selection.

So, you see, why can't humans make childbirth less painful, because you want humans to have a strong body, excellent intelligence and free hands. If you can give up these, then it can indeed reduce the pain.

Next, it’s bug-debug. Actually, there are some ideas.

03. How can you have both?

1. Caesarean section. Caesarean section is an important medical advancement. In the past, the ratio of the head to the birth canal determined that the baby's head must be maintained within a relatively stable size range.

If the head extends too far beyond the birth canal, it will cause dystocia. For pregnant women, it may cause tearing of the birth canal, heavy bleeding, etc. For babies, it may cause inability to deliver or death. Therefore, through selection from generation to generation, the baby's head and birth canal have maintained a relatively appropriate ratio, and those with inappropriate ratios have been naturally eliminated because they cause death. (Of course, a head that is too small is a disease)

However, the advent of cesarean section saved these situations. If the baby cannot pass through the birth canal (fetal pelvis disproportion), the doctor will manually make an incision in the mother's abdomen and take out the baby. This avoids death for the baby, and for the pregnant woman, it is like having an abdominal surgery.

However, there will be a problem here. That is, big-headed babies will not be naturally selected, so the gene will spread, which will lead to more and more people having difficult births. Moreover, this is not an unfounded worry, but something that has already happened.

Scientists have crunched birth data from the past 50 years and found that the global rate of fetal pelvic disproportion has increased from 3 percent of newborns in the 1960s to 3.3 percent of newborns today.

the regular use of Caesarean sections throughout the last decades has led to an evolutionary increase of fetopelvic disproportion rates by 10 to 20%.

In other words, with the advent of caesarean sections, babies with large heads can be born, but as they grow up, the birth canal does not change significantly between generations. As a result, the proportion of babies with large heads born by the next generation of mothers increases.

The higher the maternal and infant discomfort, the worse the population adaptation rate (nonsense)

Simple conclusion: The authors calculated through two models and found that the head-pelvis ratio imbalance between mothers and babies due to caesarean section increased by 20% and 9% respectively.

In other words, due to the widespread use of caesarean sections, babies' heads are getting bigger and bigger. So, maybe one day in the future, humans will really not be able to give birth naturally.

2. Brain capacity? Although there is no absolute relationship between brain capacity and IQ, from the perspective of species, relative brain capacity is directly related to IQ. In fact, we have found that many changes in human genes are related to brain capacity and intelligence.

(1) Sequence variant sites located in the 23.2-33.1 region of the long arm of chromosome 5 (rs31480, etc.) are strongly correlated with brain volume;

(2) ARHGAP11B helps basal brain stem cells to multiply, leading to the production of more neurons during human brain development and an increase in the size of the brain responsible for higher cognitive abilities such as speaking and thinking. This gene is only found in humans and our extinct relatives, the Neanderthals and Denisovans.

(3) HMGA2 gene and genes related to brain volume and intelligence.

In fact, we have made a compromise where the brain is not concentrated in development during pregnancy, but continues to grow rapidly after birth.

3. Smaller size? In fact, there is one thing we tend to overlook, that is the size advantage of the human species. There are millions of animals in nature, but there are really only a few dozen species that are larger than humans. Humans are large animals, and these tens of trillions of cells take time.

If you plan to grow the cubs after they are born, it will be tiring for the parents to take care of them (it is still quite tiring now).

4. Multiple holes? Avoid the pelvic position and grow a new hole in the human body. However, this is a bit troublesome. It is definitely not suitable to grow it on the chest, and it is not suitable if there is a spine behind the back. Then it can only be in the abdomen.

Imagine having stomach bleeding once a month. It becomes inconvenient for you to dress, and you can’t show your belly button properly.

Not to mention, there is an extra hole, and it is connected to the outside, so the problem of bacteria breeding is inevitable. In addition, there are other... Never mind, it's weird. It's better to use the original one.

This is the end of the article. The pain of childbirth is the price that must be paid as a species of Homo sapiens. If you see something that you think may be unreasonable, then you must have overlooked something more important.