Researchers at Provence University in France have discovered that a gene that reduces susceptibility to HIV occurs in greater frequency in areas of Europe that the Roman Empire did not stretch to.
The researchers have revealed that the gene lacks certain DNA elements due to which HIV cannot bind to it easily, and thus the virus' ability to infect cells diminishes.
According to them, people possessing the mutation have some resistance to HIV infection, and also take longer to develop AIDS.
Studying about 19,000 DNA samples from across Europe, the researchers found that the gene variant seemed to dwindle in regions conquered by the Romans.
The gene, which generally only people in Europe and western Asia carry, seemed to become much less frequent as the researchers moved south.
In their study report, the researchers have revealed that over 15 per cent of people in some areas of northern Europe carried the gene, compared with fewer than four per cent of Greeks.
Study leader Dr Eric Faure rules out the possibility that the Romans spread the regular version of the gene into their colonies by breeding with indigenous people.
"Gene flow between the two was extremely low," the Telegraph quoted him as telling New Scientist.
The researcher instead believes that the Romans introduced a disease to which people carrying the gene variant were particularly susceptible.
According to him, as the Romans moved north, the disease killed off people with the variant gene that now protects against HIV.
The findings of the study have been published in the journal Infection, Genetics and Evolution.