Recently, scientists have made a crazy discovery through research: according to biological laws, human ancestors originally had to be 21 months pregnant before full term. It was only in the process of species evolution that in order to survive, it was forced to give birth in October.
Supposedly, in the dangerous primeval jungle, the human ancestors should seize every opportunity to make themselves stronger. How could you choose an early birth that was not in your favor? What were the problems at that time?
Is this speculation of scientists true or false? What is the basis for this? Let's walk into the human body today and delve into the mysteries of conception.
Why do you say "all premature babies"?
Swiss biology has calculated that the degree of development and maturity of human babies one year after birth is equivalent to the degree to which chimpanzees have just emerged from the womb. Mammals such as cattle and sheep can stand for an hour at birth and will find their own grass to eat the next day.
Human babies, on the other hand, are wrapped in swaddling, with immature bones and brain capacity, requiring careful care and nursing for diapers, and can barely take two steps until they are one year old.
From the perspective of species comparison, human babies also show signs of preterm birth.
In the ancient age of Homo sapiens, the brain capacity at that time was actually larger than that of modern humans. Similarly, scientists have found that Homo sapiens babies have a brain volume of as much as 1350 milliliters, compared to about 400 milliliters for modern human infants. According to this calculation, the pregnancy cycle of human ancestors should also be longer. Judging from the speed of brain development and formation, it will not be full-term maturity until 21 months, and it is the best time to give birth.
As the only high-level intelligent species, human beings cannot fail to know this truth, so why did they make this decision and push themselves into a very unfavorable situation?
In fact, the only purpose, but for the sake of evolution, human ancestors made themselves premature babies.
To survive, shrink the pelvic bone
Millions of years ago, our ancestors were still tree creatures that ate and drank Lazarus in the trees, jumping back and forth between jungles, strong arms, and naturally used to walk on all fours.
As the environment changed and the climate became drier, humans were forced to move off the trees and onto the sparse ground of the grasslands. Exposed to no shelter, humans have become coveted prey for tigers. In order to see farther and slip faster when hunted, the ancestors evolved the ability to walk on two feet in a short period of time.
From crawling on all fours to walking upright, there are good and bad. The benefit is that the hands are free and energy consumption is minimized. One study found that humans use three-quarters less energy than chimpanzees when walking upright. Energy saving brings about the extension of human life.
Humans give priority to the development of the brain with excess energy, brain capacity is increased by nutrients, and the head circumference becomes larger. From chimpanzees with a brain capacity of 500 ml to Homo sapiens with a brain capacity of 1500 ml, modern humans even have a brain capacity of about 1.4 kg.
In order to maintain balance and not sway from side to side, humans have shrunk the pelvic bone by a few yards. The pelvic bone of the orangutan is very large, so it is crooked when walking, like a half-squat position.
In the face of the pelvic bone and the life-saving upright walk, the ancestors did not hesitate to choose the latter. I'd rather shrink my pelvic bone than evolve into Homo erectus.
If you don't give birth prematurely, you may have "one body and two lives"
This is certainly a smart choice, but it also brings an awkward contradiction between dilemmas and dilemmas. The pelvic bone is narrowed and the birth canal is narrowed so that walking can be balanced, and the brain development leads to an increase in the head circumference. If the 21-month pregnancy cycle is followed, the baby's head is easily stuck in the birth canal, posing a fatal danger.
The fetal brain volume of 385 ml is the limit that the human pelvic adjustment opening can withstand. If it is expanded, the maternal and child mortality rate will rise sharply. And the brain capacity of Homo sapiens babies has reached 1350 ml! If you wait until 21 months to give birth, it will undoubtedly directly push the mother and child to the ghost door!
Especially in primitive societies where medicine was not yet born, a little attention to mothers and babies can kill two lives. In the long run, the reproduction and growth of the entire primitive tribe will no longer be possible. Even without lion cheetahs, hominids would have automatically become extinct due to excessive childbirth mortality.
But at the same time, the human pelvis has evolved into a narrow curved shape, and it is impossible to degenerate back unchanged, not to mention that humans who have tasted the sweetness of walking upright are not willing to give up this newly acquired new skill. Such as various considerations, human beings have made a bold attempt to shorten the gestation period and let the baby out of the womb early.
After countless heavy costs, I was pregnant in October
From 21 months to 10 months, such a precise number, humans did not know it from the beginning. It is the result of repeated accumulations of maternal life. For thousands of years, women who gave birth to full term almost all died in childbirth, and humans slowly figured out solutions to try to get the fetus out early.
From 19 months to 15 months, and then slowly reduced to 10 months, the attempt in the middle of this is the painful "test product" of those women who are about to give birth, which is also the heavy price that humans pay in order to walk upright and stand at the top of the biological chain.
Therefore, the laws of nature and the mechanism of evolution set the best time for human pregnancy at 21 months, but human beings artificially advanced to 10 months in order to avoid the disastrous consequences of evolution. It's just that vaccines and modern medicine have not yet appeared, and women still have to bear the heart-wrenching pain of childbirth.
Fortunately, the new emergence of painless childbirth and water delivery can greatly reduce the pain of pregnant women in childbirth. Perhaps, this is the price that human beings have marked for brain development and upright walking, and the pain of childbirth has been engraved on generations of human beings.