Lice are the shadow of the childhood of many friends, especially people born in the seventies and eighties and before, almost everyone is not immune to lice infestation, on the head, body, once lice are almost everywhere.
In fact, not only in modern times, lice have survived on the earth for more than 230 million years, they mainly feed on the blood of mammals, and as a mammal, they have apparently plagued humans since the beginning of the emergence of human ancestors.
In most of our cognition, lice are the same, but they are on us, some on our heads, but in fact, lice are divided into three types of head lice, body lice and pubic lice, these three lice will suck blood, and their parasitic parts are different, making people unpreventable. However, lice are not useless, they help us solve the mystery of hair degradation, and these lice are relatively rare today.
Lice help us solve the mystery of hair degradation?
The direct ancestor of human beings is the Australopithecus who lived more than 30 million years ago, and this "old-timer" is very different from our current form, the most obvious of which is that they are much shorter than us, and their whole body is covered with hair, when they degenerated hair, once became a mystery.
This is because the clothes of primitive humans were mainly plant and animal fur, which were very easily degradable. However, David Reed, deputy curator of the Natural History Museum on the Florida campus, took inspiration from lice.
Australopithecus restoration
Because the lice on the human body are mainly head lice and body lice, they are all subspecies of human lice, since they are subspecies have a relatively recent common ancestor, following this idea, Reed conducted genetic testing on head lice and body lice, and found that these two lice began to differentiate from 170,000 years ago.
Although head lice and body lice are both human lice, they are already very different. First of all, body lice are not parasitic on the human body surface, but on human clothing, they lay eggs and survive in the gaps of human clothing fibers, and head lice are parasitic on human scalp.
Secondly, head lice are much smaller than body lice, and the body size difference between the two is almost doubled, and this difference in habit and body shape is obviously formed after people wear clothes, and people wear clothes to represent that most of the hair is degraded, because after hair degradation, the ability to keep warm and prevent mosquitoes deteriorates, that is, human degraded hair occurred about 170,000 years ago.
How did lice come about?
As early as 235 million years ago, insects began to branch out under the order of rodents, and in the process, they encountered the earliest mammals, and then some parasitized on mammals, at which time lice appeared.
However, the earliest lice only have two common lice and pubic lice, the so-called common lice are lice that parasitize on the animal's body, and pubic lice are lice that parasitize on the pubic hair of animals, the difference between these two lice is very large, the former belongs to the lice family, the latter belongs to the pubic lice family.
In addition to the classification differences, pubic lice are much smaller than lice, with a wider body, and are not slender like ordinary lice, this structure is because the hair in their parasitic parts is sparser, and the wider body allows them to better grasp the sparser hair.
After that, the ancestors of the human family appeared, so that the two kinds of lice came into contact with animals through human ancestors and became hosts, and then after the degradation of human hair, ordinary lice gradually evolved two subspecies of human lice: head lice and body lice.
Pubic lice
Why are lice becoming less and less common?
Once lice are simply a nightmare for humans, they suck human blood and make people itchy, although people have flexible hands to help each other scratch lice, but under the strong reproductive ability of lice, even if you spend several hours a year to catch lice, you can not completely solve the problem of lice.
However, nowadays, very few people have lice on their bodies or hair, why is that? There are three main reasons:
First: the "nightmare" of body lice. The reason why people are infected with body lice, the problem lies in the clothing, in the past people are poor, in fact, there are not many changes of clothes, which leads to a piece of clothing may have to be worn for a long time, which gives body lice the opportunity to lay eggs on clothes, eggs and hatch, so that body lice will only increase.
However, now it is different, the frequency of people changing clothes is very high, especially close-fitting clothes, so that even if there are body lice, they cannot reproduce normally. And now the use of laundry detergent and laundry detergent is also fatal to body lice in clothes.
Second: the "nightmare" of head lice. Head lice move and live by scratching on the hair follicles of the human scalp, sucking blood on the scalp when hungry, and then wantonly entangled the eggs in the hair and scalp, and even the hair follicles, especially the previous girls, because the hair is longer, the hiding of head lice is easier, coupled with the frequency of washing hair before, and there are no shampoos, so head lice are almost inexhaustible.
However, now it is different, the frequency of washing people's hair will become once a day, the laziest week also has to be twice, and the nymph growth period of head lice is a week, so that most of the nymphs are washed off when the grasping ability is relatively poor, coupled with the use of toiletries, it gives a fatal blow to the hidden eggs.
Third: the nightmare of pubic lice. The almost disappearance of pubic lice is the sum of the causes of head lice and body lice, because pubic lice can parasitize and lay eggs on underwear, so regular bathing and changing of intimate clothing also make them nowhere to escape.
Nowadays, if there are still people with lice, then it is basically related to personal hygiene, because as long as you bathe and change clothes frequently, they are difficult to parasitize.
summary
Lice and fleas, mosquitoes, etc. are the same evolution, but some lice chose human mammals as the main host, once they can coexist with humans for millions of years, because the early stage of human evolution to them helpless, just like today's cats, dogs, they simply can't get rid of, and later because of conditions, gave them a chance.
Therefore, when people's personal hygiene conditions become better today, they slowly begin to disappear, and one of the main ways of transmission of lice is from person to person, less infection, fewer spreaders, naturally less and less.