An ancient virus may promote addiction in modern people

PRECISELY what the retrovirus now known as HERV-K HML-2 (HK2) did 30m years ago, when it first infected some primates whose descendants would eventually come to be called human beings, remains a mystery. It could have caused acute illness or it may have had no noticeable effect on health at all. What is clear is that it inserted its genetic material into those animals’ genomes. And there that material remains in humans today.How this fossil DNA affects its hosts today has also been obscure. But a study led by Gkikas Magiorkinis of the University of Athens and Aris Katzourakis at the University of Oxford, published recently in the , thows some light on the issue. It shows that in some people the genes the virus left behind meddle with mechanisms associated with pleasure in the brain. One consequence seems to be that they play a part in driving individuals to addiction.