AIDS, Revised

Many researchers believe the simian version of HIV first infected African monkeys millions of years ago, giving them time to evolve their current abilities to naturally control HIV disease progression. But evolutionary biologists at the University of Arizona are turning those assumptions upside down. Using genetic sequencing to track the evolution of simian immunodeficiency virus in African monkeys and of HIV in humans in Africa, they determined that the virus took hold in animals only 200 years ago and made the jump to humans around 1908. Their findings, if accurate, rule out the notion that monkeys built immune system defenses against SIV over long periods of time, suggesting that another innate'and as yet undiscovered'process protects them from developing AIDS.