Big-eared Tutu's "ear-moving magic" is actually a kind of atavism!

Audit expert: Wu Xinsheng

Deputy Chief Physician, Department of Gastroenterology

About 6 million years ago, humans and chimpanzees parted ways in evolution; 1.8 million years ago, Homo erectus appeared; and after another million years, our species (Homo sapiens) appeared. The process of human evolution is long and complicated. Although humans today look very different from millions of years ago, we still retain some traces of evolution.

Source of Homo sapiens life scenes | Sina.com

The most obvious sign of evolution is the degeneration of body hair. Eyebrows can prevent sweat from entering the eyes, hair is to keep the head temperature stable, and although other body hairs have small contributions, such as cushioning impacts and dissipating heat, most of the body hair on people today is useless and is just a relic of evolution.

There are many trace organs on the human body

First, the cecum. The human cecum, along with the vermiform process at the end, which is the appendix, are extremely degenerate and have completely lost their digestive function. In stark contrast to humans, herbivorous mammals have a well-developed cecum. For example, the cellulose in the grass eaten by rabbits is fermented and decomposed by microorganisms in the cecum.

Source | See watermark

The rectus abdominis is a band-shaped muscle located on both sides of the midline of the human abdomen. The muscle fibers run longitudinally but are divided into several sections by several transverse tendons. For this reason, the abdominal muscles developed by people after fitness are divided into small squares.

The rectus abdominis muscle represents a relict of muscle separation. The muscles of primitive aquatic vertebrates are segmented in this way. As terrestrial animals diversified their movements, their muscles continued to differentiate and most of the myometrium disappeared, but the human rectus abdominis muscle still retains its segmented form.

Human abdominal muscles origin | Baidu

When we are frightened or feel cold, we get goose bumps all over our body. This is actually the action of the arrector pili muscles. The arrector pili muscles are the muscles that animals use to maintain body temperature and intimidate enemies. Although the hair on the human body has degenerated, the arrector pili muscles still tremble and contract.

Human ear. The location indicated by a is the remaining trace of the auriculoacoustic muscle. Source: Wikipedia

Some people can imitate the "ear movement magic" of "Big Ear Tutu", which is actually the result of the trained ear muscles. The ear movement is actually a reversion phenomenon. Like rabbits, humans could also use this muscle to move their ears individually in order to hear sounds from all directions more carefully or to intimidate enemies. Gradually, humans no longer needed such flexible ears, and this function disappeared in the process of evolution.

Source of "Ear Movement Magic" | Cartoon Big Ear Tutu

Almost all mammals have tails, and the bones at the end of the tail are the coccygeal vertebrae. Human embryos also have tails at the end of two months of development, but then the tails gradually disappear as cells die. For Homo sapiens who walk upright, the tail no longer serves any purpose, and it also affects the speed of people's movement, and even makes humans more vulnerable to being hunted by wild animals. Over time, the tail degenerates, leaving only 3-5 short coccygeal vertebrae.

The nictitating membrane, also known as the third eyelid, is a structure that protects the eyeball from dust. This structure is very common in reptiles and birds, and can be used to moisten the eyeball, clean out dirt in the eye, and also protect the eyeball. But in most mammals, the nictitating membrane has degenerated into a small vestigial organ in the corner of the eye, such as us humans.

The origin of human nictitating membrane | Guokr.com

There are many vestigial organs in the human body, such as the appendix, rectus abdominis, and coccyx. Why do these vestigial organs exist? Only Darwin's theory of evolution can provide a reasonable explanation. The existence of all these vestigial organs shows that humans evolved from animals with these organs, which also provides strong evidence for the evolution of organisms.

In addition to trace organs, humans also have "trace behaviors"

In a study of human behavior, researchers asked 4,000 people what they feared most when walking at night. The overwhelming majority of men said they were afraid of being attacked from the side, while the majority of women said they were afraid of danger from below.

Paleoanthropologists explain this phenomenon as follows: primitive females were better at climbing, usually climbing trees to collect fruits, and roosting in trees at night, so unexpected attacks often came from below them; while males slept on the ground, and the dangers they faced often came from their sides. This conclusion is surprising: we still retain the stress response caused by the living environment hundreds of thousands of years ago.

In addition, hiccups are also a relic behavior. Human respiratory nerves come from fish, and hiccups actually come from the working mechanism of amphibians when they breathe in water with gills.

Hiccup Source | Internet

In addition to humans, animals also have some organs that show signs of evolution. For example, the forelimbs of birds have become wings, which is the most striking feature of birds' adaptation to flying. Even the oldest bird fossil, Archaeopteryx, has its forelimbs transformed into wings. However, the wings of modern kiwis and ostriches, which are good at walking, have degenerated to varying degrees.

Then there are mammals that have undergone a secondary transformation into aquatic mammals, such as whales and manatees. Because distinct limbs are not conducive to swimming in the sea, they are more likely to be eaten by enemies, so they also have the phenomenon of limb degeneration. The forelimbs of whales have become fins, and the hind limbs have disappeared, but there are still traces of femurs and tibias on the bones. The forelimbs of manatees have become paddle-shaped, and the fingertips still retain traces of degenerated flat hooves.

Source: Xinhuanet

Another example is the thyroid gland of vertebrates, which evolved from the internal column of protochordates such as amphioxus, and both organs are formed from the ventral side of the pharynx during the embryonic period. The hormone secreted by the thyroid gland, thyroxine, contains iodine. Some people injected isotopic iodine into amphioxus and found that most of the isotopic iodine was concentrated in the internal column. This experiment well proves the relationship between the internal column and the thyroid gland.

In the long history of biological evolution, all the traces of evolution left behind are proof of the existence of all things in the world, and are also evidence of countless organisms' efforts to reproduce and thrive, constantly seeking to continue life and adapt to the living environment. The evolution of all organisms can be traced, and it is presented to us across millions of years of time and space, which is the mystery of life and nature.