Scientists have found antibiotic resistance genes in the bacterial flora of a South American tribe that never before had been exposed to antibiotic drugs. The findings suggest that bacteria in the human body have had the ability to resist antibiotics since long before such drugs were ever used to treat disease. The research stems from the 2009 discovery of a tribe of Yanomami Amerindians in a remote mountainous area in southern Venezuela. Largely because the tribe had been isolated from other societies for more than 11,000 years, its members were found to have among the most diverse collections of bacteria recorded in humans. Within that plethora of bacteria, though, the researchers have identified genes wired to resist antibiotics. Scientists don't really know whether the diversity of specific bacteria improves or harms health, Dantas said, but added that the microbiomes of people in industrialized countries are about 40 percent less diverse than what was found in the tribespeople never exposed to antibiotics. The vast majority of human microbiome studies have focused on Western populations, so access to people unexposed to antibiotics and processed diets may shed light on how the human microbiome has changed in response to modern culture, and may point to therapies that can address disease-causing imbalances in the microbiome. As for how bacteria could resist drugs that such microbes never before had encountered, the researchers point to the possibility of cross-resistance, when genes that resist natural antibiotics also have the ability to resist related synthetic antibiotics.