Why can an antelope on the grassland successfully plant an antelope babies without assistance, and the baby antelope can run and jump when it is born...
And women have to tear their hearts and lungs with the help of a group of midwives to tear their hearts and lungs to shout for several or even dozens of hours to give birth to a child, and it will take about a year for the child to learn to walk? Why is it so hard to have a child?
Why is it so hard to have a child?
This actually stems from a war of millions of years between evolutionary power and physical demands.
In other non-upright-walking mammals, the organs in the chest and abdominal cavity hang like a bag under the spine, and the most important role of the pelvis is to connect the hind limbs and the body, as well as the passage of the fetus during childbirth.
But as humans switch from limbs to upright walking, a new and important function of the human pelvis has emerged, that is, to support the internal organs, and this "bag" is placed directly on the pelvis in the human body. At the same time, the pelvis still plays the role of a newborn passage. At this time, we will find that these two functions are actually contradictory: the support of the pelvis requires the pelvic opening to be narrow, so as to produce enough support for the internal organs; and when giving birth, the opening of the pelvis is as large as possible, so as to ensure the smooth passage of the fetus's head.
This is the cause of this war, the evolutionary monarch feels that humans should stand up, but the internal organs are afraid of losing their support and leaking, insisting on opposing the enlargement of the pelvic opening. And childbirth is a rigid need for reproduction, what to do?
So contradictory, what to do?
So evolution jun silently accepted the status quo and came up with another trick: to make the fetus's head smaller, that is, to let the fetus be born before it was fully developed. In this way, the newborn's head will not grow too large before birth, and a squeeze can still pass through the pelvis. However, such newborns are not yet fully visual, auditory, thinking and acting, and require extremely meticulous care and years of time for the mother to develop. Nevertheless, during childbirth, the mother's pubic union needs to be separated to allow the fetus to pass, and the mother still has to endure great pain, including the tear of the birth canal.
"Stand up" no matter what.
This is a wonderful example of the contradiction between evolutionary requirements and physiological restrictions, human brain enlargement means that the fetal head is enlarged, which will bring great evolutionary advantages, but it is easy to cause the birth rate to decline because of the inability to pass the birth canal, but it has become a significant evolutionary disadvantage, and the pelvis must limit the size of the stable internal organs, so as to ensure the human ability to move. This situation, which involves the whole body, is all due to the way humans walk upright, and this is only a small part of the physical changes brought about by upright walking, and the "standing up" thing makes the human race change from head to toe. This shows that walking upright must have a significant evolutionary advantage that makes us prefer to pay such a big price and take such a big risk to stand up.
So what are the advantages? That is, walking upright makes the human forelimbs completely detached from the function of walking, become slender and dexterous, and can do some other things, such as making stone tools, carrying weapons, cooking, etc., which can greatly increase the survival rate of human beings and greatly improve the evolutionary advantage of human beings. This is why humans are willing to change their way of acting at the risk of female dystocia, lumbar and cervical spine injuries, etc.
Because the evolutionary advantages of upright walking are too great, the change in human behavior is also very rapid, so that the human body cannot fully adapt to upright walking in such a short period of time. This is where our bodies are not in tune with the way we act. If humans were still alive after hundreds of thousands of years, perhaps our bodies would change and become more adapted to walking upright.
Of course, true love is also another important reason...
Note: The picture comes from the internet, invaded and deleted.