AIDS research is filled with Holy Grails--developing a vaccine, creating drugs that can cure the disease and, for both historical as well as treatment reasons, finding out how and when the virus emerged in the first place. The earliest sample of HIV-infected human blood dates back to 1959, but before that, the HIV family tree is bare.
Scientists at the Los Alamos National Laboratory turned computers to the task, and last week they came up with what they hope is the very bottom of that tree. By measuring the rate at which the virus has mutated since the epidemic began, they calculated that HIV made its first appearance sometime around 1930. The work does not establish whether the virus showed up first in humans or in chimps, but the prevailing theory is that infected animals passed the virus on to people.
If true, the earlier date casts serious doubt on several controversial theories that purport to trace the beginning of the epidemic to the 1950s--specifically to experimental polio vaccines made from chimp tissue and tested in parts of Africa. A more likely scenario: the virus passed from animal to man during hunting and butchering when human and infected chimp blood intermingled.
While a computer model is not as persuasive as a real virus, it may be--given the lack of reliable blood samples from earlier decades--the closest researchers will ever get to the roots of the AIDS epidemic.
--By Alice Park