They do not have wings nor really effective bodies to move about. Their small legs are fit to latch onto a host and basically just stay put. Ultimately, the host becomes a village to these lice and a group of hosts become an island. Lice, therefore, begin to share the same evolutionary history as their hosts.
For example, if a population of hosts splits into two and each of the isolated populations begins to evolve into separate species, then the parasites evolve too. Two common types of lice are found on humans, head and pubic lice. Entomologists, or bug scientists, classified human head lice and human pubic lice in two separate genera because they are awfully different. Human head lice resemble chimpanzee head lice but human public lice resemble that of their gorilla counterpart.
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This discontinuity between the two types of lice was curious to the authors of this paper. One would expect both types of lice to be more similar to chimpanzees since they are the closest evolutionary ancestor to us. So the authors of this paper, as Carl says it,. They analyzed DNA from human head lice, human pubic lice, as well as other species from the same genera that live on chimpanzees and gorillas.
They also analyzed DNA from lice that live on monkeys and on rodents so that they could get a better sense of how pubic lice had evolved from a common ancestor with other species. The scientists not only drew branches for each species, but also estimated when those branches split over the course of history. Their conclusion… We did not get pubic lice from other hominids.
We got them from the ancestors of gorillas. Actually, in the last hundred years ago or so, humans transmitted what is now HIV from our chimpanzee counterparts, probably from some sort of sexual contact or blood exchange… And why that even happens in modern days opens a whole new discussion on gene flow and species concepts one that Wilkins addresses,.
Templeton, Alan R. The meaning of species and speciation: A genetic perspective.
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- 1. Introduction.
- Pediculosis and Pthiriasis (Lice Infestation): Background, Pathophysiology, Etiology.
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- Crabs (Pubic Lice).
In Speciation and its consequences , edited by D. Otte and J.
Sunderland, MA: Sinauer. March 8, at am. Along the same lines as ebola transferring to humans? Kambiz said:. So, where did we pick up these unwanted blood suckers in the first place? All signs point to a human—ape connection, and "connection" may mean something more tangible than an evolutionary link. Some studies suggest interaction between early Homo species and gorillas, and also between early Homo species and us. The lice we carry around are sucking lice. Two subspecies we harbor, head lice and body lice, belong to the Pediculus picture left genus Pediculus humanus capitis and Pediculus humanus humanus , respectively.
The other species we harbor, you know, down there, is a member of the genus Phthirus. Our closest living relatives, the chimpanzees, harbor Pediculus , as well, while gorillas are home to another Phthirus species. Sucking lice have been sucking primate blood for at least 25 million years. The big story, though, is what happened about 6 to 7 million years ago, and in the case of the gorilla, even later. Humans and apes are supposed to have parted evolutionary ways at about the 6 million year mark.
The Pediculus genus seems to have split at the same time, with Pediculus schaeffi hitching a ride with the chimp lineage, and Pediculus humanus sticking with what would become the Homo line. The gorillas split off a little earlier, maybe about 7 million years ago, and the Phthirus may have done the same, sending Phthirus gorillae with the gorillas natch , while Phthirus pubis eventually became a human problem.
Things get a bit, well, sticky when it comes to the Phthirus line Phthirus pubis - picture right , however. The split between the gorilla and human lice seems to have happened around 3 to 4 million years ago, millions of years after the gorilla and human branches parted ways. That means that at the 3 to 4 million year point, human ancestors and gorillas must have had some kind of…contact. The authors who uncovered this finding note in their paper that "How we might have acquired our pubic lice from gorillas is not immediately apparent, however it would be interesting to know whether the switch was very recent say less than , years old or whether it was considerably older" Reed et al.
Yes, that would be interesting indeed to know. There are a couple of ways to explain why we carry around a chimp-related genus and a gorilla-related genus of lice. One idea, felicitously dubbed the " pair of lice lost " model, poses that after apes and humans parted ways, each lineage carried both Pediculus and Phthirus. Somewhere along the way, goes the pair-of-lice-lost idea, chimps dropped Phthirus and gorillas dropped Pediculus. Humans, being the avaricious little lineage that we are, held onto both. In other words, the explanation that fits better is the "recent host switch" idea, as in it switched hosts from gorilla to us thanks to direct contact.
Predation or overlaps in habitats each species used also could have been a way the lice jumped from gorillas to us. That transfer might have been possible thanks to a few changes the Homo lineage was experiencing, including loss of body hair. As their hirsute habitat decreased, the Pediculus subspecies that would become the head louse retreated to the head. That may have left a bit of an opening for a Phthirus invasion. Phthirus simply may have encountered the least competition, you know, down there.
Speaking of competition, the history of Pediculus humanus suggests a bit of fancy business happening between Homo sapiens and archaic Homo species, possibly Homo erectus. The Pediculus genus encompasses two lineages that trace back 1. One of the lineages underwent a bottleneck—a severe population reduction—right about the time modern Homo sapiens did, , years ago. The other lineage, however, spent 1. The only way for them to have gotten back together after that long hiatus was direct physical contact.
Are Pubic Lice Really Going Extinct?
It could have been more of that predation or shared hangout that let the two louse lineages reunite. But this re-pairing of a pair of parasites pairasites? The irresistible inference is that when the lice lineages reunited through the direct contact of Homo sapiens and archaic Homo , so did the lineages of several other unwelcome guests. While the evolutionary history of lice helps us trace our deep past, we can also use them to explain more recent developments, such as the advent of attire. Body lice hang out—literally—in clothing, and pinpointing when this Pediculus subspecies separated from its head-bound brethren may have helped pinpoint when Homo sapiens decided to put on some clothes.
Fig leaves aside, the question has been wide open, with ranges from 40, years ago to 3 million. But recent work indicates a divergence between the Pediculus subspecies at , years ago. This timing puts clothing far earlier than many estimates and well before humans would have needed them for warmth.
Speaking of the Bible, Egyptian mummies and mummies of other provenances have proved to be a wealth information about the evolution of the human-specific louse. And the mummies also tell us a lot about what our ancestors had to deal with. In two Peruvian mummies dating to about CE, for example, one specimen had lice on its head, while the other had Indeed, mummified lice are among the "best-preserved human parasites," enthused one researcher, yielding not only adult lice but also nits and even eggs.
Specimens from Israel dating back years were culled from hair combs, while crab lice…otherwise known as pubic lice or Phthirus pubis the gorilla kind , have been found on South American mummies. For many years, lice experts thought that pubic lice were not a New World problem until the Europeans brought them, along with all of their other Old World threats. Then, in , researchers found Phthirus pubis eggs attached to the pubic hairs of a year-old Chilean mummy, and adult pubic lice have been found in clothing from a year-old Peruvian mummy.
The lice were stuck to the pleats of some cloth from a female mummy, and the enthusiasm of the authors in describing the louse specimens is worth transmitting in their own words Rick et al.
Both are females. The foreleg is quite slender, with a long fine claw. The mid and hind legs are strong with thick claws, and the characteristically compressed abdomen is wider than it is long.
CDC - Lice - Pubic "Crab" Lice - Biology
It remains unclear why P. The louse with the "long fine claw," they conclude, likely made its way to the Americas with early human migration. It seems that they can also appear in other hairy places, including the legs, arms, armpits, and face. Yes, face. Crab lice can take up residence in the eyelashes , where they produce a crusty deposit and red, itchy eyes. As is appropriate for a sexually transmitted usually organism, the slow-moving pubic louse is known for becoming attached to the same pubic hair for quite a long time.
A true romantic, indeed. Gross, L. Yong, Z. The geographical segregation of human lice preceded that of Pediculus humanus capitis and Pediculus humanus humanus. Reed, D.
BMC Biology , Toups, M. Molecular Biology and Evolution 28 1 : 29— Raoulty, D. Journal of Infectious Diseases 4 : — Reed D. PLoS Biol 2 11 : e Robinson, D. Parasitology Research 90 3 : — DOI: Mumcuoglu,, Y. Journal of Medical Entomology 25 6 : — Rick, F. Journal of Parasitology 88 6 : — Zinsser, H.