Sydney, February 7 : A study of lice from 1,000-year-old mummies in Peru suggests that the parasites had accompanied their human hosts in the original peopling of the Americas, probably, as early as 15,000 years ago.
Writing about their findings in The Journal of Infectious Diseases, the researchers have revealed that the DNA of the lice obtained from the mummies matches that of the most common type of louse known to exist across the world now and before European colonization of the New World.
The new findings suggest that Europeans might have introduced diseases, most notably smallpox and measles, but not the most common of lice, as had been suspected.
The evolutionary biologists envision that the new research technique may become a tool in studying other mummies for valuable insights into human migrations and the spread of disease.
The Peruvian mummies were among those collected between 1999 and 2002 in the high coastal desert of southern Peru by anthropologist Sonia Guillen.
The DNA tests were conducted on lice recovered from the two mummies in two laboratories, both providing identical results. The researchers say that the tests showed that 11th-century Americans already hosted the prevalent type-A strain of lice that infests head and body.
According to them, "the most likely theory" at present is that type-A lice originated in Africa and were distributed worldwide long ago. Type-B that infests only the head is also common, and type-C is rare, known primarily in Ethiopia and Nepal, they say.
Pubic lice are an entirely different strain, the researchers add.
Lice from other mummies with hair still intact, the scientists said, may "help us understand the distribution of types A and B in the Americas and the Old World before globalisation," they say.
David Reed, an evolutionary biologist from the Florida Museum of Natural History in Gainesville, said that despite the discovery of type-A lice in pre-Columbian America, early European explorers might still be implicated in spreading a louse-borne disease back to the Old World.
"The typhus bacterium may be native to the Americas. There are no records of typhus in Europe until the 1500s," the International Herald Tribune quoted him as saying.