About 6 million years ago, humans and chimpanzees parted ways in evolution; 1.8 million years ago, Homo erectus appeared; and another hundred million years later, our species (Homo sapiens) appeared. The evolution process of human beings is long and complicated. Although human beings today look very different from those millions of years ago, we still retain some traces of evolution.
The most obvious trace of evolution is the vestigial body hair. Eyebrows can prevent sweat from entering the eyes. Hair is used to keep the temperature of the head stable. Although other body hairs have small contributions, such as cushioning impacts and heat dissipation, most of the body hairs on people today are useless, just left over from evolution things.
There are still many trace organs on the human body
First is the cecum. The human cecum, together with its end vermis, that is, the appendix, is extremely degenerated and has completely lost its digestive function. In clear contrast to humans, herbivorous mammals have a well-developed cecum. For example, the cellulose in the forage eaten by rabbits is fermented and decomposed by microorganisms in the cecum.
The rectus abdominis is on both sides of the midline of the human abdomen. It is a band-shaped muscle with longitudinal muscle fibers, but it is divided into several sections by several transverse tendons. For this reason, the abdominal muscles trained by people after fitness are divided into individual sections. small cube.
The rectus abdominus represents a residual muscle separation phenomenon. The muscles of the relatively primitive aquatic vertebrates are segmented in this way. With the diversification of terrestrial animal movements, the muscles continue to differentiate, and most of the sarcomeres disappear, but the human rectus abdominus remains segmented.
And the goosebumps we get all over our bodies when we’re scared or cold are actually the arrector pili muscles working. The arrector pili muscle is the muscle that animals erect to maintain body temperature and intimidate the enemy. Although the hair on the human body has degenerated, the human arrector pili muscle still trembles and contracts.
Some people can imitate the “ear-moving magical skill” of “Big Ear Tutu”, but in fact it is the trained ear-moving muscles that are working, and the ability to move the ears is actually an atavistic phenomenon. Like rabbits, at first humans could use this muscle to move their ears independently, in order to hear sounds from all sides more carefully, or to intimidate the enemy.
Gradually, humans no longer need such flexible ears, and this function has disappeared in the process of evolution.Cowboys outclass Colts 54-19 with a 33-point fourth quarter.
Almost all mammals have a tail, and the bone at the end of the tail is the coccyx. Human embryos also have tails at the end of two months of development, but the tails will gradually disappear as the cells undergo apoptosis. For Homo sapiens who walk upright, the tail no longer plays any role, and it will also affect the speed of human travel, and even make human beings more likely to be hunted by ferocious beasts, and it will degenerate over time, leaving only a short 3-5 joint tail vertebra.
The nictitating membrane, also known as the third eyelid, is a structure that protects the eyeball from dust. In reptiles and birds, this structure is very common, and can be used to moisten the eyeball, clean out the dirt in the eye, and also have the function of protecting the eyeball. But in most mammals, the nictitating membrane degenerates into a small trace organ in the corner of the eye, such as us humans.
There are still many trace organs like the cecum, rectus abdominis, and tailbone in the human body. Why are there these trace organs? Only with the viewpoint of Darwin’s theory of evolution can a reasonable explanation be made. The existence of all these trace organs shows that humans evolved from animals with these organs, which also provides strong evidence for the evolution of organisms from the side.
Beyond Trace Organs, Humans Have ‘Trace Behavior’
In a study of human behavior, researchers asked 4,000 people what they feared most when walking at night. The overwhelming majority of men responded that they were afraid of being attacked from one side of the body; the majority of women responded that they feared danger from below.
Regarding this phenomenon, the explanation given by paleoanthropologists is: females of primitive humans are better at climbing, and usually take the task of climbing trees to collect fruits, and they also perch on trees at night, and most of the accidental attacks come from below the body; while males If you sleep more on the ground, the danger you face often comes from your side. This conclusion is surprising: we still retain the stress response caused by the environment we lived in hundreds of thousands of years ago.
In addition, hiccups are also vestigial behaviors. Human breathing nerves come from fish, and hiccups actually come from the working mechanism of amphibians when they use gills to breathe in water.
Another example is the thyroid gland of vertebrates, which evolved from the inner column of the original cable animals such as amphioxus, and these two organs are formed from the ventral side of the pharynx during the embryonic period. Thyroxine, the hormone secreted by the thyroid gland, contains iodine. Someone injected the isotopic iodine into the amphioxus, and found that most of the isotopic iodine was concentrated in the inner column.
This experiment well proved the relationship between the inner column and the thyroid gland. In the long river of biological evolution, all the evolutionary traces left behind are proofs of the existence of everything in the world, and it is also the evidence that countless creatures strive to reproduce and continue to find evidence of life continuation and adaptation to the living environment. The evolution of all creatures has traces to follow, and the unfolding of time and space spanning millions of years is the mystery of life and nature.