Hitchhiking Virus Reveals Pattern of Ancient Human Migration from Africa

Today, humans have spread across the globe, taking over almost every continent on Earth. Yet that wasn't always the case. Our ancient ancestors were once clustered on one continent. Now, scientists have found proof of the "out-of-Africa" pattern of human migration with the help of a common human virus.

Our ancient ancestors first emerged from Africa roughly 150,000 to 200,000 years ago. By studying the human genome, researchers have been able to tell that from there humans spread eastward toward Asia and westward toward Europe. While the researchers managed to find this general pattern, though, they haven't been able to pinpoint exactly how this spread occurred--until now.

The virus that the researchers decided to focus on is called herpes simplex virus type 1 (HSV-1). In fact, researchers have previously studied HSV-1 by looking at a single gene, or a small cluster of genes. But this particular method can be misleading, which is why scientists decided to take a bit of a closer look. This virus usually causes nothing more severe than cold sores around the mouth. And yet a study of the full genetic code of this virus has revealed exactly where humans may have first travelled after they first appeared in Africa.

In order to examine this virus a bit more closely, the researchers compared 31 strains of HSV-1 collected in North America, Europe, Africa and Asia. More specifically, they used high-capacity genetic sequencing and advanced bioinformatics to analyze the massive amount of data from the 31 genomes.

"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," said Curtis Brandt, one of the researchers, in a news release.

The new research shows that humans came from Africa to the Middle East and then spread from there. In fact, the new analysis shows some intricacies of the migration. For example, they found a HSV-1 sample from Texas that looked Asian rather than European, unusual for the area. Either the sample had come from someone who had travelled from the Far East, or it came from a native American whose ancestors had crossed the land bridge across the Bering Strait about 15,000 years ago.

"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," said Brandt in a news release. "The dates match, so we postulate that this was an Amerindian virus."

The findings reveal a little more about the patterns of ancient human migration. In addition, they show that a virus can be used to track these patterns and that the out-of-Africa hypothesis is correct.

The findings are published in the journal PLOS One.