A new study shows that humans' tendency to drink alcohol might come from our primates' ancestors. The study published last month revealed findings that support the "drunken monkey hypothesis." Between June to September 2013, researchers observed the eating tendencies of black-handed spider monkeys for 12 hours each day on Barro Colorado Island in Panama. The monkeys are probably not getting drunk, University of California, Berkeley biologist Robert Dudley, who co-authored the study , said. In a 2014 book, "The Drunken Monkey: Why We Drink and Abuse Alcohol," Dudley explained some fruits eaten by primates have a "naturally high alcohol content of up to 7%." But he did not have data illustrating apes or monkeys sought out and preferred fermented fruits. "It (the study) is a direct test of the drunken monkey hypothesis," Dudley said in a news release. "Part one, there is ethanol in the food they're eating, and they're eating a lot of fruit. Then, part two, they're actually metabolizing alcohol — secondary metabolites, ethyl glucuronide and ethyl sulfate are coming out in the urine. What we don't know is how much of it they're eating and what the effects are behaviorally and physiologically. But it's confirmatory." This story appeared in dozens of media outlets. For more, see our press release at Berkeley News.