At present, there are two different hypotheses about the origin of modern Homo sapiens, namely, the African hypothesis (also called substitution theory) and the multi-regional evolution theory: the substitution theory holds that modern Homo sapiens moved out of Africa and was quickly replaced by other human species without cross-breeding; Multi-regional evolution holds that modern homo sapiens appeared when modern homo sapiens came from different regions and mated with ancient homo sapiens. There is also a neutral hypothesis that when modern people from Africa spread all over the world, they interbred with other ancient humans.
Researchers believe that the history of lice can meet the third hypothesis. In this study, Clayton and David Reid of the University of Florida compared the mitochondrial DNA of lice with published data on human evolution. The analysis shows that two kinds of human lice with different genes appeared1180 thousand years ago. Clayton thinks that these two subclasses will separate when two kinds of human beings (probably Homo erectus in Asia and Homo sapiens in Africa) split. The evolution of lice into subspecies means that there is no connection between them, which means that their human hosts are also separated, which is inconsistent with the multi-regional evolution theory. But these data also show that there was some contact between different kinds of early human species. Therefore, lice thought to live on Homo erectus jumped on Homo sapiens at some time before the extinction of the host-this conclusion also weakened the substitution hypothesis.
Although the founders of the multi-regional evolution hypothesis disagree with this new explanation, Chris Stringer, a paleontologist at the Natural History Museum in London, supports it. He believes that this research has opened a new window for the study of human origin.
There are three kinds of lice: one is body lice, the "body" of the body, and the other is head lice, which is our head. The third kind is crab. These three kinds of crabs are basically similar in individuals, so their shapes are basically similar. They just have different living environments, habits and life spans. Diseases that lice can spread can be divided into two main categories. The first type is epidemic typhoid fever, which is caused by Poisson rickettsia. Lice like to spread rickettsia. The main symptoms of this disease are high fever, headache, cold stomach and fatigue, and red congestive papules often appear four to six days after the onset. This kind of disease, we know that typhoid fever is actually a very serious disease. The second disease is relapsing fever, which is caused by spirochetes. Its main symptoms are chills, that is, frequent chills all over the body, sometimes high fever, high fever, headache, joint pain in the back and feet, skin and mucous membrane bleeding, and frequent nose bleeding. Within a day, after sucking the patient's blood, the spirochete in his intestine suddenly disappeared in the digestive tract. In fact, the spirochete has entered the body of its lice through the intestinal wall, and reappeared six days later, multiplying in large numbers. Spirogyra, which can fill all parts of the body cavity of lice, is very large, but it has no effect on lice itself. However, when lice suck human blood, they will spread spirochetes, leading to relapsing fever. Its main habit is that body lice are mostly parasitic in the gaps between our chest hair, armpit hair, pubic hair and underwear; Head lice, mostly parasitic in the roots of hair; Most crabs are in pubic hair. Lice suck human blood every day, so they suck human blood many times a day. When a patient has a high fever, lice will escape from the human body to find a new host, that is, to find a new person who is not sick. At this time, it has played a role in spreading and spreading diseases. Body lice can lay 270 to 300 eggs in a lifetime, so head lice can lay 80 to 1 10 eggs, and crabs can lay 26 eggs, so their reproductive ability is also great.
To prevent lice, we must first do a good job in cleaning and hygiene, do our own cleaning and hygiene, change clothes frequently, wash your hair frequently and take a bath frequently. In addition, we should also do a good job in the hygiene of the family environment, so we should always wash the floor and carpet and clean all kinds of environment at home. Second, kill lice at high temperature, so that when lice are found, we can kill adults, nymphs and eggs of lice at a temperature of 65 degrees, and the purpose of preventing and controlling lice can be achieved as long as 15 to 30 minutes. The third is drug fumigation. You can't use it casually, you need to do it under the guidance of experts. Commonly used drugs are methyl formate and other drugs, which are relatively safe for people and animals, but their dosage and duration should be carried out under the guidance of experts. In addition, there are Chinese medicines. Stemona in traditional Chinese medicine has a good insecticidal effect on lice. Stemona Stemona soaked in alcohol is often used to kill lice with good results.