Mummies With Lice Offer New Clues to Human Migration
for National Geographic News
|February 8, 2008|
A common type of head lice picked from thousand-year-old Peruvian mummies suggests the pesky parasitic insects accompanied modern humans on their first migration out of Africa, according to a new study.
Researchers had thought Europeans brought the widespread louse species to the Americas about 500 years ago, said David Reed, who studies the parasites at the University of Florida's Museum of Natural History in Gainesville.
Hundreds of lice were found on two mummy heads dating from the ancient Chiribaya culture that were excavated from the southern Peruvian coastal desert between 1999 and 2002.
Reed and his colleagues expected the lice collected from the mummies' braided hair to be of a kind called type B, which is abundant in North and Central America.
"We thought the type B lice might have their origin here in the Americas and perhaps have been the only one here prior to European influence," Reed said.
The team was surprised to find the more widespread louse, type A. This supports the notion that the lice "spread around the globe with humans as they emerged out of Africa," he added.
(See an interactive map of ancient human migration.)
Where and when the type B louse originated remains a mystery.
Reed and colleagues reported the finding this week in an online edition of the Journal of Infectious Diseases.
Type A and B lice are the varieties that afflict school-age children in much of the world. A third type, C, is rare, limited to Nepal and Ethiopia.
The presence of type A in the Americas prior to European arrival also raises the possibility that a louse-borne disease called epidemic typhus may have originated in the New World.
Typhus is characterized by a skin rash and high fever and has caused epidemics that killed tens of thousands in Europe from the 16th to the 19th century.
The disease is carried by type A lice, but not all type A's carry it, Reed explained.
"This might be one of the few diseases that went against the grain of colonization and spread from the New World back to the Old World," he said.
(Read related story: "Did Columbus Bring Syphilis to Europe?" [January 16, 2008].)
In future research, Reed and colleagues will examine lice found on mummies from various cultures for DNA of the bacteria that causes typhus.
"That would be the smoking gun," Reed said. "If we were able to find evidence of the disease in the Americas prior to Columbus, then we would know for sure that the origin of the disease was here."
Vince Smith is a louse expert at the Natural History Museum in London who was not involved in the new study.
He said the research "opens up a lot of possibilities for doing ancient epidemiology and epidemiological studies on the transmission of louse-borne disease."
"It's not something that we've been able to do a great deal of before, simply because it's extremely difficult to extract DNA from louse specimens that are this old. The DNA in lice tends to degrade very quickly," he added.
Reed and his colleagues also plan more studies on louse genetics to glean insights into human migration patterns.
In particular, they will look for fast-evolving genes that are likely to differ from one population to the next and use population genetics to infer when each population moved.
"We're hoping that we can sample more lice in Siberia and Mongolia, for example, and lice from mummies, especially from the Americas," he said.
Genetic connections between ancient lice in these various populations would solidify theories that the first Americans originated in Siberia and Mongolia, he noted.
"So we're scouring museum collections, looking at mummies, and trying to collect lice from them," he said.
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