Scientists have debated, since such discussions were made permissible, the origins of the human species: did we come from Asia? Africa? Maybe even the Middle East?
Until very recently, many of these theories had equal merit. However, a study of the complete genetic code of the herpes simplex virus type one (HSV-1), notorious for its oral cold sores, has confirmed the theory that the human species emigrated out of one location: Africa.
The study is available online in the journal PLOS-ONE and was conducted by several specialists, including two professors of Ophthalmology from the University of Wisconsin-Madison's School of Medicine and Public Health: Aaron W. Kolb (who also does Visual Sciences), Curtis R. Brandt (who specializes in microbiology and immunology), and Cécile Ané of the Departments of Botany and Statistics at the University of Wisconsin-Madison.
The three authors compared 31 different strains of HSV-1 that were sampled all across the world from North America to Eurasia and Africa. "The result was fairly stunning," Brandt said. "The viral strains sort exactly as you would predict based on sequencing of human genomes. We found that all of the African isolates cluster together, all the [sic] virus from the Far East, Korea, Japan, China clustered together, all the viruses in Europe and America, with one exception, clustered together."
He continued: "What we found follows exactly what the anthropologists have told us, and the molecular geneticists who have analyzed the human genome have told us, about where humans originated and how they spread across the planet."
The scientists hope the technology they used in analyzing 31 complete viral genomes may help us to understand why certain diseases can have a sudden lethal turn. "We'd like to understand why these few viruses are so dangerous, when the predominant course of herpes is so mild. We believe that a difference in the gene sequence is determining the outcome, and we are interested in sorting this out," Brandt said.
Oh, and that "one exception" that Brandt mentioned? A single strain of HSV-1 sampled in Texas came out of the gene sequencer looking Asian. "How did we get an Asian-related virus in Texas?" Aaron Kolb pondered. Since some Native American ancestors traveled across the Bering Land Bridge to settle in modern North America, Brandt believes that to settle the mystery.
"We found support for the land bridge hypothesis because the date of divergence from its most recent Asian ancestor was about 15,000 years ago," Brandt says. "The dates match, so we postulate that [the exception] was an Amerindian virus."
If you want to read the release, you can find it here.[Image via the study and its authors on PLOS-ONE]