Why don’t babies start walking immediately after birth? Why, unlike animals, does it take a whole year for a person to get on his feet? Anthropologist John Bock.
“A foal stands up an hour after birth. A newborn baboon clings tightly to the wool of its mother, who jumps with him from branch to branch. The baby monkeys closest to humans (chimpanzees and bonobos) are much more agile from early infancy than children, who take an average of a year to master the skills of walking. What is the reason?
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By the time of birth, the human brain is underdeveloped to a much greater extent than in other mammals. And he is simply not able to control complex muscle movements. In order to stand up immediately after birth, the child would need to stay in the mother’s stomach for much longer. Which is impossible for two reasons: the first is that a person has too much brain volume, the second is that the capabilities of the female pelvis are limited. Nine months of pregnancy is the optimal ratio developed in the process of evolution.
История вопроса
Unlike his distant predecessors, man walks on two legs. There are many suggestions that explain the sudden emergence of this new body position. The most reliable hypothesis is that bipedality allowed our ancestors to more productively settle into new territories and spaces, for example, in the savannahs. Even if the ancient people were physically close to monkeys, the vertical position and walking on two legs with a straight back led to a change in the shape and size of the body. The female pelvis, for example, has shrunk significantly, making childbirth more difficult and even dangerous for mothers and babies.
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At the same time, bipedalism led to other changes: hands were freed. Ancient man began to use tools, explore new territories, increase social contacts and exchange. Due to this, the brain began to increase significantly in volume. However, these two evolutions – an increase in the size of the brain and a decrease in the size of the female pelvis – contradicted each other. The critical moment has come: if the brain, and therefore the human head, continued to grow in the womb, the woman and the child would die during childbirth. And even the optimal size that we have come to in the process of evolution leads to the fact that the child’s head is forced to shrink during the difficult and long passage through the mother’s birth canal.
Immature birth
Yet nature seems to have found a graceful way out of the circumstances. According to Kenyan paleoanthropologist Richard Leakey*, our children are born prematurely, both physically and in terms of brain development. The muscles and joints of the baby do not complete their development by the time of birth, the neck does not accumulate enough tone, and the brain takes time to complete its formation. The time of birth is somewhat close – otherwise the very large head of the baby will not be able to pass through the relatively narrow pelvis of the mother. An interesting fact: the volume of the brain of an adult becomes three times larger than at the time of birth, while the brain of a chimpanzee only doubles.
Conclusion: our children continue to develop intensively even after they are born. That is why they depend on their mother and other people much more than newborn babies of mammals and primates.
John Bock is an anthropologist at the University of California at Fullerton (USA).
* For details, see R. Leakey’s The Origin of Humankind (Perseus Books Group, 1994).