Studies have previously suggested that people started drinking alcohol about 9,000 years ago, around when we invented the means of making it. But new research suggests we could handle the stuff far before that: more along the lines of 10 million years, the Los Angeles Times reports. Humans have a powerful version of the digestive enzyme ADH4, which is needed to metabolize booze. Similar animals like the orangutan and baboon, whose version of the enzyme doesn't work so well for handling booze, would have been too sickened by alcohol to develop an interest in it.
But 10 million years ago, an ancestor of today's gorillas, chimpanzees, and humans developed a kind of ADH4 that's about 40 times as powerful when it comes to metabolizing alcohol, allowing us to handle moderate quantities, Science reports. And hominoids who started descending from trees around that period might have found that fermented fruits left on the ground were actually pretty palatable, and perhaps even offered some giddy side effects. "We always wondered why some primates became terrestrial and not others,” says a researcher. “So to find out that they had an adaptation that allowed them to eat fermented, fallen fruit, it fits in so perfectly.” Those side effects, of course, aren't always so helpful.