Conspiracy theories be damned, said AIDS star Dr. David Ho. A study he cowrote in February's Nature asserts that HIV reared its ugly head in Central Africa in the late '40s -- not in an American germ-warfare lab as the KGB once claimed and as Louis Farrakhan still does. The search for signs of HIV in 1,213 long-frozen blood samples turned up the earliest known case in a Bantu man who died in the Belgian Congo in 1959. There are now an estimated 20 million HIVers in the region.

"This is the oldest, totally unambiguous look at HIV," said Dr. Simon Wain-Hobson, of Paris' Pasteur Institute. A genetic analysis revealed that the sample resembles a forebear of several of the 10 distinct HIV subtypes (lettered A to J) found worldwide. In the developing world, B is the dominant strain; D is most common in Africa. "This is no doubt an ancestor of B and D," Ho said.

The finding is of more than just historic interest, since it allows researchers to eyeball HIV's decades-long evolution from parasite to plague. "This snapshot may help HIV vaccine efforts," Ho said, "because we can reasonably predict how the virus will evolve."