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What are the interesting evolutionary residues in the human body?


Which is the most perfect human body in the world?

Is David by Michelangelo? Or is the Vitruvian man in Leonardo da Vinci?

Or look at the modern ones, looking for them from the modern training science bodybuilders?

Unfortunately, even the eight packs that modern aesthetics pursue are actually products of evolution.

The connective tissue-separated muscle is commonly found in fish, and most of the muscles of the terrestrial chordate have lost their segmentation, but this remains remains on the rectus abdominis.

Although it sounds incredible, none of the entire Homo sapiens species is perfect.

"Perfect body" is simply a pseudo-proposition. After all, the human body is not created by God according to his own preferences.

Even the human beings who think they are the most advanced are full of flaws, a fact that is difficult for the perfectionists and creationists to accept.

Generally speaking, to understand history, we must find the remains left in the birth and development of civilization.

But if you want to understand the history of evolution, we don't need to go to the wilderness to look around and see if we can.

Human beings, which are popularly considered to be a highly evolved, advanced creature, stand out from the body form and the way they live.

Despite this, many remains of organs remain in our bodies, and each of them is related to evolution.

Some of these ruins have long been familiar.

For example, Shanwei , when we first knew it from our parents, the "useless" and "excess" labels were already posted.

The appendix is ​​located at the rear end of the cecum, originally an organ used by mammals to digest plant fibers, and later lost its status due to a shift in diet.

*Note: The appendix is ​​not a completely redundant and useless organ. Modern research has found that the appendix has immune function, and it can also provide shelter for some probiotics to protect the health of the gut flora.

Another example is the human ear. This is a well-preserved evolutionary site. The exquisitely unearthed artifacts are amazing.

The first is the Darwin point remaining on the outer edge of the auricle, with a small protrusion on the inner upper edge of the rear of the ear.

It is the part of the ear tip of a higher animal, and humans no longer have such a pointed ear, but still retain this part.

Below the auricle, we also retained three otolary muscles.

This is clearly what our mammalian ancestors used to control the auricle orientation to better alert the danger.

The human auricle has changed a lot, and there is basically no possibility of changing the orientation. These three muscles have become furnishings.

Many people are unable to control these three otolary muscles autonomously. Only a small number of people can re-understand the skills and use the legacy left by this ancestor.

Moving in the direction of the face, we can find the ear-blind tube, which looks like a small hole with unknown meaning.

This is the product of the incomplete closure of the first arch in the embryonic development stage. It originated earlier than the Darwin point and was the remains of the fish ancestors.

The ear-blind tube is a congenital malformation in modern times. Although it looks very inconspicuous, don't ignore it. Once an infection occurs, you are expected to thank your ancestors for 180 million generations.

In addition to these relatively obvious ancient relics on the ears, there are some organs that we talk about every day but do not know that it is also an evolutionary residue.

Chicken skin is a reaction we often encounter, either because it is scared or because it feels cold.

Perhaps no one will take the initiative to explore the significance of this reaction, at most in the biological textbook to remember the "skeletal muscle war, chest muscle contraction, increased thyroid hormone secretion" of the human body cold mechanism.

In fact, the vertical hair muscle is the muscle that makes the hair erect. For our furry ancestors, it is normal operation to fry hair by some external stimulation.

But our human hair is not very competitive, not able to thrive, although the muscle is still the muscle, the hair is not the hair.

Many animals still retain the reaction of “fried hair”. The most common thing is that the cat arches the body and raises the hair when it is fearful, making itself as bulky as possible.

And people have more complex and advanced emotions than these animals, and the reason for chicken skin is not limited to fear.

It may be that you read a wonderful sentence in the novel, or you may hear an amazing melody, which obviously has nothing to do with fear.

The reaction of the hairy muscles may help us find the origin of these high-level emotions. After all, the chicken skin is also a natural reaction after completing the "great harmony of life".

In addition, there are some redundant organs that can directly swell the face of the creationist supporters.

The Bible tells us that the Lord God has used a picture of his own to squeeze out a man and give him life.

Then God felt that a person was too lonely, so he made a woman with a man's rib.

If the story is really like this, why should a man have a mammalian organ similar to a woman?

Is it because God is personally nurtured for future generations? Or is God special about nipples?

This question is not a good answer. As the chairman of the Anti-God Creation Alliance, Darwin did not explain this problem well.

He only made a guess that the former mammals were both parents and breast-feeding offspring, and later the male nipples were degraded for some reason.

In fact, the root cause of a male being born with a nipple is that the default gender of human development is female.

This sex determination mechanism comes from the XY sex chromosome we are familiar with.

The first four weeks of embryonic development are not gender-specific, and they are all coded according to the gene coding of the X chromosome.

The genes of the nipple and mammary gland are on the autosome, so in this period, both men and women will grow nipples indiscriminately.

It was not until the fifth week that the embryo began to form gonads, but this is still no gender difference.

At the seventh week, the sex-determining gene on the Y chromosome was expressed and the gonads began to develop into testes.

If it is a female baby without the Y chromosome, the gonad will develop into the ovary according to the default female gender until the 13th week.

Simply put, the development of the mammary papilla is completed before the embryo's sex differentiation, even if the mammary gland is useless for men, it is not convenient to delete later.

This also shows that the male mammary gland is not a degenerating organ, but only maintains the undeveloped state before puberty.

If stimulated by estrogen, it can still develop into a fully functional mammalian organ.

This developmental mechanism of human embryos may be to improve developmental efficiency. After all, saving embryonic development time can lead to greater survival opportunities.

But this will also bring some obvious defects.

Although the male testicle is located near the penis, the spermatic cord connecting the two has a large circle in the abdominal cavity.

This has led to males being more prone to suffocation, and some of the intestines may fall into the scrotum, causing great pain.

The reason is that the gonads of the distant ancestors of human beings are in a higher position, such as the shark's gonads growing near the liver.

The gonads formed in the early stages of human embryos are still the same, but we all know that both the female ovary and the male testicle should be placed lower.

Therefore, during the development of the fetus, the gonads are constantly moving down, just like re-evolution.

For women, the ovaries only need to move down to the lower abdomen, while the male testicles are moved down to the abdominal cavity, which is inevitable.

There are many factors that can cause the testicles of a baby boy to not move down into the scrotum when the final fetal development is completed, called cryptorchidism.

The testicles they hide in the body are difficult to produce sperm properly because of the high ambient temperature, and are dozens of times higher than the normal testicular cancer.

If the fetus is accompanied by hypospadias and abnormal sex hormones, it is likely to be raised as a girl, and it is too late to be discovered until adulthood.

However, normal development of the testes is not necessarily perfect.

As the testicles descend through the weak areas of the body wall to the scrotum, this process not only allows the spermatic cord to wrap around the pubic bone, but also leaves a fragile breakthrough for the body wall.

When the abdominal pressure rises, the intestines may break through the weak body wall and fall into the scrotum.

The cause of rising abdominal pressure may be the crying and coughing of children.

Adults, on the other hand, gradually become more prone to suffocation due to the thinning of the body wall.

Clinically, in addition to male-specific scrotal hernia, the incidence of male inguinal hernia is much higher than that of females, with a ratio of approximately 12:1.

The fish ancestors were not just so simple to dig a suffocating pit, they also sent us a snoring spree to us with our amphibious ancestors.

The snoring here is not the kind of snoring that squanders the excess air in the stomach, but the involuntary muscle snoring.

We inherited the phrenic nerves that the ancestors of the fish control to breathe, and inherited the reflexes of the trachea when breathing from the amphibious ancestors.

Fish are breathed with sputum, and sputum is located near the neck, so the phrenic nerve that controls breathing follows the principle of proximity and is emitted from the neck.

In the amphibious class, they have evolved their lungs and can breathe on land.

However, amphibian larvae are still inseparable from water, and there is also a stage in which sputum and lung coexist.

For example, sputum, basically use the external hemorrhoids to breathe before metamorphosis, but they also have lungs. The phrenic nerve must close the trachea when controlling breathing to ensure that water does not enter the lungs.

This kind of protection mechanism has also been passed on to human beings, but human beings have no shackles. When this protection mechanism is stimulated, there will be snoring.

From the sputum to the lungs, the organ controlled by the sacral nerve has moved down a lot, but the starting point of the nerve is still in the original neck.

This means that the phrenic nerve will be very tortuous, and the nerve fibers are also of extraordinary length. Any problem will cause snoring.

If the neck and the chest are far away, it is understandable to pull a long nerve. The famous recurrent laryngeal nerve may break through your cognitive bottom line.

The recurrent laryngeal nerve is emitted from the brain and connects a large number of structures in the neck, mainly controlling the movement of the throat, including swallowing behavior and daily vocalization.

It is reasonable to say that the path from the brain to the throat is very short, and there should be no difference.

In fact, the recurrent laryngeal nerves on our left and right sides have taken a surprisingly detour.

The recurrent laryngeal nerve on the right side is going to bypass the carotid artery, and the recurrent laryngeal nerve on the left side is even more so that it extends down to the vicinity of the heart, bypassing the aorta and returning to the throat, which is the origin of the recurrent laryngeal nerve.

This incredible layout is once again inseparable from our fish ancestors.

Our recurrent laryngeal nerve belongs to the fourth vagus nerve branch in the ancestors, under the sixth arterial arch, and the nerves and arteries do not interfere with each other.

Here, the terrestrial animal is here, the sixth arterial arch retreats to the chest, and the recurrent laryngeal nerve has to be bypassed from below, forming the dead state today.

Humans should be glad that the neck is short, and the recurrent laryngeal nerves are not too long.

Look at the long neck of the giraffe, and the recurrent laryngeal nerve is 4.56 meters, which is probably the most sinful animal.

Seeing here, the bitterness in the heart of the Dragon of Heaven is coming out.

However, it has been obsessed with the secular, and the words of the esoteric words are not worth mentioning, and they have not finished the 28-meter recurrent nerves with a thousand words, and quickly closed their mouths.

If you are a perfectionist, if you read this article again, I am sorry to have buried a thorn in your heart.

In fact, although we always advertise ourselves as a miracle in the history of biological evolution, it is the highest level of creatures that have appeared on Earth.

But the cruel reality still reminds us that human beings are still a fish, a frog, and a beast in a sense.

We have been a primitive creature of the magic revision for a million years. Although our functions are more complicated, there will be more hidden dangers in the revision process.

*Reference materials

Neil H. Shubin Feng Zejun (translation). The evolutionary flaws of amphibians from amphibians. Global Science, No. 2, 2009, 42-45.

Yang Anfeng. A Brief Discussion on the Evidence of Comparative Animal Anatomy[J]. Bulletin of Biology, 1981(03): 1-3.

Tenke. 16 fatal flaws in human evolution [J]. Yue Di Digest, 2008 (03): 49.

Jerry Coyne .The longest cell in the history of life. Why Evolution is True.