New research has pushed back the origins for our affinity for alcohol (more accurately our ability to process larger quantities of ethanol) way, way back to the last common ancestor of humans, chimpanzees, and gorillas (~10 mya). A paper out in the Proceedings of the National Academy of Sciences (PNAS) last week has mixed up social media, with Science News‘ report on the paper being extensively shared on facebook and twitter. It was previously believed that the ability to process larger intakes of ethanol evolved very recently in modern humans, no earlier than 9,000 years ago, at the onset of fermentation practices. These new and exciting results bring up a lot of interesting points for the evolution of not just social behavior, but also diet, habitat exploitation, and even locomotion.

Unfortunately, or luckily for those primates involved, our earliest ancestors are too old school to be posting their pictures on Facebook. Regardless, monkeys drinking drunken monkeys (1 oz triple sec, 1 oz banana liqueur, 1 oz melon liqueur, 1 1/2 oz cranberry juice, 1 1/2 oz pineapple juice) would probably regret adding their moms on Facebook after only a few sips. According to the study, only the living African apes (gorillas, chimpanzees, and modern humans), and their extinct close relatives and ancestors possessed the ability to process ethanol in high quantities at a fast rate. That means the other apes, gibbons and orangutans, as well as monkeys and prosimians would have been, “a cheap date,” according to scientist Matthew Carrigan (Santa Fe College).

The authors argue that with a cooler, dryer earth towards the end of the Miocene the last common ancestor of gorillas, chimps, and humans would have been more likely to climb down out of the trees of an ever thinning forest. On the ground, our ancestors were encountering slightly rotten fruit that had begun to ferment, and therefore had a higher alcohol content than the fruit still hanging on the branches. Here, they suggest, is where the ability to process alcohol became advantageous. Those who lacked the new mutation had a build up of ethanol in their bloodstreams when they ate the fallen fruit, making them drunker and sicker. Over time, the ones who could have a few and still make it home up in the trees for bed out-reproduced those sleeping it off on the ground and this ability rose to be present in all living descendants of this ancestral population today.

Finally, the authors suggest that the relationship between alcohol and food sources for our earliest ancestors may be why humans today have an association with alcohol and the pleasure centers of the brain. So next time your buddy has one too many and doesn’t seem to be able to process his alcohol, go ahead and call him a monkey. You and your ability to walk in more or less a straight line is a testament to your exploring ape ancestors who first came down to the ground for a party 10 million years ago.