September 24, 2021

There are tens of millions of animal cubs that can take care of themselves. Humans are the smartest. Why are cubs so difficult to raise?

Calves can walk independently when they are born, and they know how to find milk to drink; horse cubs and deer cubs can trot with their parents in an hour; whales and dolphins can swim to the surface to breathe when they are born.

These natural self-care abilities are not possessed by humans who are also mammals. In addition to crying and crying, newborn babies leak all the “things” in their bodies. Humans are so smart, why are babies worse than calves?

Humans are all “premature babies”

Compared with other mammalian cubs, newborn babies do not seem to be fully developed. Many biologists refer to the first few months of a baby’s birth as the fourth stage of pregnancy, but even if it counts for two more years, it is no better than the cubs of other animals.

It usually takes 15 to 18 years for babies to take care of themselves from landing. During this period, they need the careful care of their parents to survive in the world. Without parents, the howl on the ground is the death knell, the bell for the beast to eat.

We call ourselves Homo sapiens. A large proportion of brain capacity is one of the main characteristics of human beings and the basis of high intelligence. However, the brain of a newborn baby is only 30% of the adult brain, and the closest chimpanzee with us reaches 40%.

The immature brain may be the main reason why human cubs cannot take care of themselves. Here comes the question: Why do humans with larger brain capacity have the smallest brain capacity in infancy?

Is it true that the female birth canal restricts the development of the baby’s brain?

In TV dramas, the delivery room often hears the voice of “I see my head, my head comes out”. If the baby’s brain is not 30% of adulthood, but 50%, there will be a high probability of “stuck, unable to get out” in the delivery room.

For a long time, scientists believe that the main reason for the small head of a baby is the width of a woman’s pelvis, which determines the size of the birth canal. Humans have another main feature-walking upright. The result of this evolution causes the female pelvis to contract inward. If a woman’s pelvis is wider, it will affect the efficiency of walking and running upright.

In the past, the old man always looked at his daughter-in-law’s back and said, “It’s so big, you can give birth at a glance.” This kind of empirical talk, the scientific principle may be that the pelvis is wide, the head is not easy to get stuck, and it is easy to grow. However, in the primitive period, women with the advantage of pelvic width would become a beast’s meal because of their slow movement. Therefore, the primitive man’s empirical talk should be: “It’s really big, and it will live soon after seeing it.”

Eventually in the evolution process, women with narrow pelvis and fast running survived, and babies could only be born prematurely to ensure that their heads would not get stuck. This explanation is very logical, and seems to be a compromise solution after the game between natural selection to help humans survive and reproduce. But is this really the case?

Human metabolism hypothesis

In the past hundred years, with the continuous development of human anatomy, scientists have found that human mobility depends on the local movement efficiency of the limbs, and the pelvis has minimal influence. At the same time, scientists have also found that many women’s pelvic (birth canal) openings can accommodate larger heads. In other words, when the baby is in the mother’s belly, there is still room for the brain to develop, but it seems to be restricted by some kind of power, and can only come into the world with a smaller head.

Human growth is inseparable from energy. The placenta at the beginning and the baby with all five internal organs need different energy.

All living things in the world have their own energy metabolism rate limits. At the same time, organisms also have a minimum limit, which is called the basal metabolic rate (BMR). The maximum limit of ordinary people’s metabolic rate is 2 times the basal metabolic rate (BMR). The peak state of athletes can reach 4 to 5 times the BMR, but it cannot be maintained for a long time.

This is like an overclockable CPU (central processing unit). Increasing the power can break the rated calculation rate and perform overload computing. Human women are like CPUs. Being pregnant means extra energy metabolism. When they are “overclocked” for nine months, the placenta will have an adult metabolism rate close to twice the BMR. This is the limit state. If the baby does not come out, it will not be able to afford it. , The final outcome may not be big or small. This is not the only answer, energy is just one factor.

Higher plasticity

The brain of a normal person cannot fully mature until it reaches 25 years of age. Studies have shown that it is precisely because the baby’s brain is immature that makes it more plastic. If a newborn calf is a piece of colored paper with a lot of information written on it, a human baby is a blank piece of paper. The white paper appears to be incompetent for babies, forcing human parents to take care of them every step of the way and continuously input information to them.

This information is not simply basic avoidance of beasts or walking skills. This process is accompanied by brain development, which means that there is more copying and more abstract learning ability, which can instill the experience summed up by the ancestors from the shallower to the deeper, making humans more and more it is good. This kind of survival advantage can form a positive feedback in the survival of the fittest, so it evolved into the breeding advantage of the population, which has been retained to this day.

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