Listening to the past for thousands of years, this is a very vulgar question. But on second thought, this is a scientific question. But I didn't understand science when I was a child. All I know is that dogs eat shit is a historical story, which my mother told me. It's a little circuitous It was the Dragon Boat Festival in the early days of the Cultural Revolution. According to our local dietary customs, fried dough sticks, stir-fried horns and fried rice cakes were supposed to be fried, but everyone was short of oil. Usually only a few drops of oil are put in cooking, and the fried food needs half a pot of oil. Then the neighbors can only gather in the shade to swallow or even drool, thinking and talking about fried food. Suddenly someone said, "At this moment, Jiang Qing must be giving Chairman Mao fried dough sticks." Everyone agreed, but suddenly there was silence. Everyone realized that this sentence had serious political problems, and after a moment of silence, they quietly left. Fortunately, no one reported it. The next day, my mother steamed steamed steamed bread, half a spoonful of white flour and two spoonfuls of corn flour. At that time, there were white corn and yellow corn, but farmers were unwilling to plant them because yellow corn could not pretend to be white flour. White corn can't be found now, only in the germplasm gene bank of breeders. Now all the crops are yellow corn. The "yellow" of yellow corn is carotene, which can be converted into vitamin A in the body and is more nutritious than white jade rice. Mother kneaded the dough into the shapes of ears of wheat, ears of wheat, ears of corn, chickens, rabbits and pigs. I looked at it, puzzled and asked. Mom said: you can't fry fried dough sticks without oil, and steam them instead; Pinch these patterns, steam them and put them on the confession table for confession, praying that the grain will be plentiful and the six animals will flourish. The original statue was posted on the confession wall, and the portrait of Chairman Mao was posted at that time. The chickens, rabbits and pigs pinched by my mother are as lifelike as if they were alive. I asked, can you give me a play? Mom said that if you miss, you can't spoil the food. God will punish you when he sees it. I don't understand, ask, how did God punish me? Next, my mother told me the story that dogs eat shit. A long time ago, there was a woman steaming steamed bread, and her child was crying. In order to coax the children, she pinched a noodle bench for them to sit on and a noodle dog for them to play with. As expected, the child was not naughty, but she took a shit on the noodle stool. Suddenly, it was cloudy and windy. This is God's anger. A long time ago, wheat grew like sesame seeds, with ears of wheat from bottom to top, so people couldn't finish all the white buns and rotten noodles every day, so many people wasted food. This woman is just one of them. Unfortunately, God saw her. The wind from God touched the ears of wheat from bottom to top and said, "If you touch them, you won't waste food." The dog of this family saw and heard it, and quickly stood up and kept bowing and kowtowing to God. The woman also saw and heard, and quickly picked up the child and walked into the yard. Mother and son knelt down and kept bowing and kowtowing to God. God stopped stroking the ears of wheat, but Yu Nu did not disappear. He said to the dog, "if there is less food, you can eat shit in the future!" " He also said to the woman, "food is scarce, so many people are not fed." You and your children will be entrusted to the dog generation in the next life! " "The clouds opened and the wind stopped. The woman took the child and the dog to the field to see that there was only one ear on the top of the ear of wheat. From then on, there was only one ear of wheat. From then on, dogs began to eat shit. Since then, people who waste food have been entrusted to dogs in their next life. I believe this story. But when I was a child, there was not enough food to eat, and no one wasted food. I think everyone should listen to God. I thought, God, you are so cruel. Have mercy and let the wheat grow like sesame. When I grow up, I realize that this is not a historical story, but a fable, which is used to educate people. I also understand the scientific question "Why do dogs eat shit". It turns out that 0/00% digestion of human intestines and stomach can't absorb all the nutrients. Human excrement contains protein and fat. The better people eat, the more nutritious the excrement is, but the more smelly it is. But dogs don't feel smelly, and they may feel more fragrant. Babies suck milk and shit is more nutritious. When they call a dog, they run over. For five thousand years, food was often not enough, and dogs had to eat shit. Other animals eat shit, too. It's nature, it's instinct. For example, if pigs eat chicken manure, the chicken intestines are short, the absorption rate is low, and the nutritional value of chicken manure is higher. Now I'd rather believe this fable is true. It is obvious how common waste is at the table. In the restaurant, save face and waste at least 20%. Family members, who are pseudo-healthy, think that overnight meals produce nitrite, which will cause cancer, so they are all dumped. The nutritionist who promotes this statement is guilty. In fact, a large number of bacteria will produce nitrite, and the food in the refrigerator will not breed a large number of bacteria in a short time. The overnight food is taken out of the refrigerator and eaten hot, which is completely harmless. Over the past 30 years of reform and opening up, the waste from hotels to families has become more and more serious. It is said that the garbage on the dining table in China can feed 50 million people a year, which is equivalent to the population in the prosperous Tang Dynasty. In ancient times, it was a prosperous time to have enough food for 30 years in a row, but today's waste is actually equivalent to the grain output of the ancient prosperous time. It can be seen that the level of productivity is not what it used to be, and that today's waste is unprecedented. In ancient times, people in prosperous times never forgot their poor years in good years, and they never forgot their hunger when they were full. Many people misunderstand the "stink" in Du Fu's poem "Drunk Wine and Meat in Zhumen". There are two explanations for "smelly" in ancient times. Here, it doesn't stink, it doesn't stink, it doesn't waste, but it smells good. This poem was written after the "An Shi Rebellion", and the prosperous age is no longer there. " There are frozen bones on the road ",which is luxurious and not wasteful compared with Zhumen wine and meat. Of course, there was waste in ancient times, such as extravagance and waste in the Western Jin Dynasty, but there was very little waste in ancient times, so it had the value of entering history, and it was only recorded in history as a shame. Nowadays, waste is common and there is no sense of shame. Will it be wasted when the economy develops? But why don't hotels in developed countries in Europe and America waste? This has something to do with culture. There is still vanity in our culture. Then let's say something barbaric and curse this vain inferiority: let the people who waste food have dogs in the next life! Let them eat shit!