From a biological point of view, under what circumstances do people cry?

Why do people cry? What effect does tears have on human body? What's the point? This seemingly simple question has long puzzled researchers. Charles Darwin, the founder of the theory of evolution, believes that tears are a kind of "relic" of evolution, which has nothing to do with the competition for survival in the process of evolution. Darwin's analysis: When crying, the microvessels around the eyes will be congested, while the small muscles will contract to protect the eyes, thus making the lacrimal gland secrete tears. Darwin believed that tears themselves are meaningless "by-products" for the human body. However, American anthropologist Achille Montago holds the opposite view to Darwin. He believes that tears are beneficial to the human body and have a certain influence in evolution, so they can be passed down from generation to generation through natural selection. Human tears are the result of the survival of the fittest. Montague, for example, said: Tears contain lysozyme, which is a self-defense substance of human body and can protect nasopharyngeal mucosa from bacterial infection. Observation shows that dry crying without tears is easy to make nasopharyngeal mucosa dry and infected. With the rapid development of science and technology, human beings landed on the moon, and more and more exquisite asexual reproduction also allowed human beings to "create" animals. However, some seemingly simple questions, such as "Why on earth do people laugh", are still unclear. Dr Ramachandara of the United States has made a new exploration in this field. When listening to a joke or a funny thing, you may think that there will be some kind of result, but often the ending is another matter, so you have to explain it again fundamentally. It can be seen that people tell people around them by laughing that what just happened was a "false alarm". According to this theory, if someone steps on a banana peel and falls on his head, you won't laugh, but if he gets up again after falling, pats himself and continues on the road, you may laugh-in fact, this is to tell people around him with a smile that there is no need to help him at all. It turned out to be a "false alarm." Dr Ramachandara discovered this "false alarm" phenomenon while treating a woman with strange encephalopathy in India. She giggled when he pricked her skin with a needle. In this regard, he analyzed that if the needle touches a normal person, the pain signal received by the skin will be sent to the part of the brain responsible for responding to pain, and then the information will be transmitted to the sensory center in the brain from there, and finally it will feel pain. But for the woman, the information only reached the pain center of the brain, but not the sensory center, because the connection between the two was abnormally cut off. So she just felt a little pain, not a sharp pain, and her brain could only interpret it as "a false alarm", so she giggled.