Why do people cry when they are sad, and why do they cry when they are happy?

It is often said that; happiness, anger, sadness and joy, people's feelings. Even a strong character of people, there will inevitably be tears, or tears of sadness. Moreover, people will not only cry when they are sad, but also when they are happy and excited. To explore the specific reasons for tears, or "heroes do not shed tears lightly", or "tears in front of the flowers, under the moon sadness", people are very different from each other. Anthropologists have found that among the many species of primates, human beings are the only ones who can cry and shed tears. Shedding tears is a simple behavior that people are born with, no need to learn, everyone will, just like the heart beats, the kidneys excrete as instinctive, like sighing, sneezing as spontaneous. So why do people shed tears? What does shedding tears do for the human body? What is the significance? This question seems to be simple, but it is a puzzle that has long puzzled researchers. Charles Darwin, the founder of the theory of evolution, once hypothesized that Charles Darwin, the founder of the theory of evolution, once hypothesized that tears are some kind of evolutionary "relics" that have nothing to do with the competition for survival in the evolutionary process. When you cry, the microvessels around your eyes become engorged with blood, and small muscles contract to protect your eyes, causing the lacrimal glands to produce tears. Darwin believed that for the human body. Tears themselves are meaningless "by-products". American anthropologist Ashleigh Montague's view is the opposite of Darwin. He believes that tears have a beneficial effect on the human body, this benefit has a certain effect in evolution, and thus can be preserved through natural selection from generation to generation, humans will shed tears is the result of the survival of the fittest. He said, for example: tears contain lysozyme, which is a kind of self-defense substances, it can protect the nasopharyngeal mucosa from bacterial infection. Observations show that dry crying without tears can easily dry out the nasopharyngeal mucosa and become infected. Today, more and more scholars agree with Montague and believe that the act of shedding tears may have certain benefits for the human body, and University of Minnesota psychologist William. Frye conducted a more comprehensive study of tearing behavior from a psychological and biochemical perspective. He divided tearing into reflexive tearing (e.g. stimulated by onions) and emotional tearing. Over a period of five years, William . Fry studied thousands of "volunteer" subjects who shed tears. His statistics showed that men rarely cried more than 7 times in a month, while women cried more than 30 times. The vast majority of subjects cried for 12 minutes at a time, with the occasional "record" of up to 1 hour and 40 minutes of continuous crying. The highest frequency of emotional tearing occurred between 7 and 10 p.m. in the evening, in the company of family and friends, or while watching television. According to self-report, about 45% of men often go a month without crying once. And only 6 percent of women may go a month without crying once. 40% of women's crying is due to arguments, marriage, love and other relationships. Men cried only 36 percent because of relationships, and significantly more than women cried over movies, television, book content and unexplained depression. Frye collected tears from subjects in small, specially designed test tubes and analyzed the tear samples for testing. He found that tears from emotional tears contained more proteins, while tears from reflexive tears contained fewer proteins. Among these structurally complex proteins was a chemical that was hypothesized to be possibly analogous to painkillers. Based on this result Frye speculated that tearing may be an excretory behavior. It can eliminate biochemical toxins that are caused and accumulated in the body due to emotional stress, and these toxins will be detrimental to health if they are not eliminated through tears and remain in the body. Emotional tears excrete toxins and restore psychological and physiological balance to the tearful person, thus providing health benefits. However, what exactly is the composition of the toxins excreted through tears? What are the functionally different proteins contained in tears? How are they produced and how are they metabolized? Even Fry himself was not sure. Figuring out these questions will help people determine whether Frye's theory is correct. So why are humans the only primates that shed tears? In 1960, British anthropologist Prof. Alister Hardy made a sensational proposal to explain why humans are the only primate species that shed tears, but the explanation seems to have eluded researchers for a long time. In 1960, the British anthropologist Prof. Alister Hardy put forward a sensational hypothesis of the sea ape. The previous theories of human origins all believed that the stage for the birth of human beings was the forest and grassland. The theory of the origin of human beings was based on the forest and grassland, but the theory of the origin of human beings was based on the fact that the sea-ape, which is the most common species in the world, was born in the forest and grassland. This particular physiological phenomenon, which is also characteristic of sea animals, is a vestige of the ancient sea ape stage of the human body. Animals that evolved and developed on land in the absence of salt could not have developed this physiological characteristic of "wasting" salt. Prof. Hardy's ape hypothesis was considered "fanciful" when it was first proposed. However, over time, this hypothesis has not been refuted, but on the contrary, more and more researchers believe in this hypothesis. 1983, the University of Melbourne, Australia, biologist Prof. Pilic Danton study compared the physiological mechanisms of human and other mammals to control the salt balance in the body, and his research also suggests that human tears may originate in the salt secretion mechanism of the lacrimal glands of sea animals. The sea-ape theory is perhaps the only theory that can explain the origin of human tears. However, due to the lack of reliable fossil evidence, this theory has not yet been accepted by most anthropologists. It has not yet been accepted by most anthropologists. As an evolutionary hypothesis of the origin of human beings, the ape theory needs to be further improved. How did human tears originate? Why do people shed tears? Although researchers have explored this from different angles, these questions are still scientific mysteries. It can be said that the serious study of the behavior of tears, and now only just started, to solve the secret of tears, to be in all aspects of the researchers of the **** with efforts. So what do tears do? Everyone's eyes are manufactured in the tears of the "small factory", people gave it a name called "Lacrimal gland". Every day, the lacrimal gland keeps making tears. Tears can be very useful, blinking, tears on the eyeballs evenly wiped on the eyeballs play a moist role. Tears can also wash away the dirt on the surface of the eyeballs, to keep the eyeballs clean, tears also have the role of killing bacteria. So it's okay to shed a few tears once in a while, whether it's a man or a woman, it's a way of relieving stress and soothing emotions. Tears also have the effect of cleaning the eyeballs and brightening the eyes, no wonder my eyesight is so good, is it because of more tears, ha

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