Steve Jones, intrepid explorer of Darwin's Island

The geneticist explains why Darwin would be jumping for joy today and how the fight against Aids may imperil us all

About three-quarters of the way through our conversation, Steve Jones tells a story about the history of the Aids virus that ends with Charles Darwin jumping for joy. Jones himself is not a protagonist. He's the narrator, and that's the point.

The story begins in 1981, when HIV was first identified in the San Francisco Bay area in California. Every month since then the virus has been exhaustively sampled so that scientists can now trace its genetic development over 28 years. They can also extrapolate backwards from 1981: “You can look at the evolution of the virus, then you can make a diagram and draw a line all the way back and ask, ‘Where does this line hit zero?' In other words, where is the granddaddy of all these different viruses?”

The line hit zero in about 1897. That turned out to be a year of massive expansion of Leopoldville - then capital of the Belgian Congo - now Kinshasa, which was good supporting evidence for the theory that the Aids epidemic began around then because the virus needs a critical mass of humanity to spread quickly.

But the clincher came later. Four years ago an American researcher went to Kinshasa to study pathology samples in the local hospital and found one from a young man who died of an unknown disease in 1959. “The researcher looked at the DNA and there it was, HIV. The man had died of HIV. Extract the HIV from that sample and put it on that line and it sits bang on the line, exactly where it should have been for 1959. It's amazing. If you were Darwin you'd be hopping up and down with joy.”

The detective work that people have done on the Aids virus is “mind-blasting”, Jones says, and I understand just enough about it to be as excited as he is. In fact I'm so enthralled by the idea that you can use genetic mutation to track back more than a century from San Francisco to Africa and identify to within 50 miles where Man was first bitten by an Aids-infected chimp, that for a moment it's possible to forget what the virus has done to humankind in the interim. (Jones doesn't forget. He taught for a year in Botswana in the 1970s and points out that his students, who should now be in their fifties, are all dead.)

Professor Jones is probably Britain's leading geneticist and definitely one of science's most gifted communicators. He works at the cutting edge of an intensely important and fashionable field of research and he also teaches, broadcasts, pontificates and writes mass-market science books.

http://entertainment.timesonline.co.uk/tol/arts_and_entertainment/books/non-fiction/article5617852.ece