Some unique organs in the human body have lost their functions in the process of evolution, such as wisdom teeth, appendix, and some trace organs in the ears.

According to the research of neuroscientists, there is a degenerated muscle behind our human ears, which is the trace of the neural circuit that can make our ears move after hearing the sound.

Cats and dogs can turn their ears in that direction to hear more clearly after hearing interesting sounds. After human evolution, the pinnae muscle has lost the ability to turn the auricle.

More than 30 million years ago, after the primate's nose evolved in the direction of dryness, the human auditory organs began to undergo great changes. As the ears become smaller, the related muscle tissues become different.

According to a research paper published by Steven Huckleberry Zhun, a professor at the University of Missouri, apes have lost the ability to move their auricles back and forth freely in the process of human evolution.

1908, scientists found that some muscles in the outer ear or the back wall of the auricle also move with the left and right rotation of the line of sight.

Through the investigation of these active muscles, it is found that when the eyes rotate, the ears do rotate in the direction of listening to sounds because of the reflex nerves, but this activity is extremely weak and cannot form an action that can be observed by actual vision. In the later experiment, after adding the sound of interest, a weak current can be detected in the scar of the muscle behind the ear (mentioned earlier).

It can be said that these muscle scars are basically useless, but for psychologists and neurologists, they may have certain significance in the study of evolution and brain.

The discovery of auricle direction and some muscle marks that control ear rotation is helpful to the study of human hearing. Moreover, although it is completely independent and has no practical function, it reveals a new side of nature and brings new hope to the theory of studying the development of nerve and genetic factors.

The research results of micro-organ structure may be helpful to the treatment and research of hearing-impaired children. More surprisingly, it may also be an objective measure of adults' positive emotions.

Even if this method is no longer used now, it can still play a role in the study of evolution and brain for psychologists and neuroscientists.

What is a trace organ?

In the Origin of Species, Charles Darwin first mentioned the remaining organs after evolution, that is, the trace organs in the human body structure. He believes that trace organs were necessary for survival in the past, but with the passage of time, they gradually shrank and lost their functions, which is the evidence of evolution.

The human appendix is a good example. The appendix is a small sac extending from the large intestine and an organ left by the ancestors of the herbivorous system. It is an indispensable organ of herbivorous vertebrates, so basically herbivorous vertebrates have large appendices.

Our ancestors had bigger jaws than us, and wisdom teeth were inherited from that time. Although it is also a trace organ, it may have played a great role in replacing dental caries and broken teeth for our ancestors who did not pay attention to oral hygiene at that time or even centuries ago.