The Coevolution of Lice & Their Hosts

eldavojohn writes "It might be an uncomfortable subject but parasites are an interesting subject when it comes to evolution. Ever wonder if pocket gophers have lice? Well, they do. And most interesting of all is the evolution of these lice mirroring the evolution of gophers. To study the genes of lice may shed just as much light on evolutionary trees as studying the genes of the actual host the lice has evolved to. The most unsettling result from these studies is that human head lice and human pubic lice (crabs) vary so greatly that they are in two separate genera. There were similarities between our pubic lice and the lice found on gorillas. Scientists came to the conclusion, which they published today in BMC Biology, is just as striking as their earlier one about head lice. But it is hardly the same. We did not get pubic lice from other hominids. We got them from the ancestors of gorillas."

Comments

hmmmmm

[User 956]

There were similarities between our pubic lice and the lice found on gorillas.

Look, I don't know what these scientists have been doing with the gorillas in this study, but this seems like evidence of *something*.

Dating the first clothing

[lawpoop]

I remember something from my days of getting an anthropology degree where some scientists was trying to guess the approximate date when humans first started wearing clothing. Tools made from bone and rock last a long time, so you can easily get a good idea of when people started making new types of tools. But stuff like clothing, rope, or weaving rots away pretty quickly, so finding them in archaeological digs is pretty rare.

IIRC, there are two types of lice or fleas. One kind lived on human skin and hair, and the other preferred clothing and blankets and lived only in artificial fabrics. The scientists were trying to see when the fabric-preferring bugs diverged from a common ancestor by examining the genetics. Really clever!

"Ever wonder if pocket gophers have lice?"

[Daniel Dvorkin]

To be perfectly honest ... um, let me think about this ... no.

Re:"Ever wonder if pocket gophers have lice?"

[modecx]

My pocket gopher had lice once. It was very irritated.

So many responses, so little time...

[jpellino]

"We did not get pubic lice from other hominids. We got them from the ancestors of gorillas."

#10. Speak for yourself, professor.

#9. "coyote-ugly", move over...

#8. Shhh... Hear that? I think Dave Attell's head just exploded.

#7. Why is the waiting room empty? All I said was we...

#6. "Scratch-a while you can, monkey-boy!"

#5. Next on Springer...

#4. Time to bring the crab-infested brass monkeys in off the back porch, Radar.

#3. Yes, you heard me right, I need to get into those crabs' genes.

#2. Let's say we ask Jocelyn Elders to weigh in on this one.

and #1... Well I'll be a monkey's uncle, and a mighty itchy one at that.

(N.B., I know gorillas are apes not monkeys, so save the posting effort, it's just a freaking joke...)

Re:hair shape

[mastershake_phd]

"In Africa, where the percentage of children with head lice is higher, lice have adapted their claws to better grasp elliptical hair"

It looks like its an arms race then.

Timing when we lost our hair

[doubletruncation]

From the article: "And then there is the matter of where the lice live. Today, lice live on little islands of hair on an ocean of hairless human skin. They are clearly adapted to our relatively hairless bodies. The authors suggest that their results may mean that hominids were already losing hair 3.3 million years ago. The gorilla lice needed an empty ecological niche--pubic hair--that they could occupy in order to survive. If hominids had full-body hair, the lice that already lived on it might have been able to outcompete an invader."

In my opinion this is one of the most interesting aspects of this research - being able to date when we started becoming hairless. It's always been a puzzle why we are relatively hairless compared to the other great apes, and I would guess that being able to put some time constraints on it is a step toward understanding how this happened.

Re:hair shape

[Xonstantine]

It looks like its an arms race then.

That's exactly what parasite-host relationships are. Evolution isn't so much a march in a straight line, but a vicious cycle of decimation-immunization-regression to naivete-back to decimation, ie, the Red Queen hypothesis. The really interesting thing is the degree to which parasites have affected evolution. A lot of secondary sex characteristics, because of their biological expense, are really good indicators of parasite resistance.

Rather than read a second-hand account...

[GrumpySimon]

Rather than read a second-hand account (although Carl Zimmer is very good), the original article is open access and is available here: http://www.biomedcentral.com/1741-7007/5/7/abstrac t

Conclusion:

Reconciliation analysis determines that there are two alternative explanations that account for the current distribution of anthropoid primate lice. The more parsimonious of the two solutions suggests that a Pthirus species switched from gorillas to humans. This analysis assumes that the divergence between Pediculus and Pthirus was contemporaneous with the split (i.e., a node of cospeciation) between gorillas and the lineage leading to chimpanzees and humans. Divergence date estimates, however, show that the nodes in the host and parasite trees are not contemporaneous. Rather, the shared coevolutionary history of the anthropoid primates and their lice contains a mixture of evolutionary events including cospeciation, parasite duplication, parasite extinction, and host switching. Based on these data, the coevolutionary history of primates and their lice has been anything but parsimonious.