Chimpanzees drink nearly two daily cocktails from fermented fruits

In a landmark study, researchers from the University of California, Berkeley, and related institutions examined the dietary habits of wild chimpanzees in Uganda and Côte d'Ivoire. This research aimed to provide a better understanding of the relationship between primates and alcohol consumption. By analyzing 21 species of fruit commonly eaten by chimpanzees, the team found that these animals consume approximately 14 grams of pure ethanol daily through their fruit-based diet, which consists largely of figs and plum-like fruits. The findings highlight a significant quantity of alcohol intake, equating to nearly two standard drinks for humans, adjusted for body size. To gather data for their study, scientists faced substantial challenges due to the difficult field conditions, including limited electricity and high humidity which threatened their instruments. Over three seasons, they meticulously collected and calibrated test kits to measure the alcohol content in various tropical fruits. This research marks the first instance of direct chemical measurements of ethanol in chimpanzee diets, offering insights into their unique foraging behaviors which may influence their attraction to fermented foods. The findings prompted discussion about the broader implications of alcohol consumption among primates. Robert Dudley, the senior author of the research and a professor at UC Berkeley, posited the 'drunken monkey hypothesis,' suggesting that ancient common ancestors of humans and chimpanzees likely had diets rich in alcohol, influencing our modern tendencies toward alcohol consumption. The study raises crucial questions about whether chimpanzees are intentionally selecting fruits for their alcohol content or simply prioritizing sugary options, which could indicate an even higher alcohol consumption rate. Furthermore, the research indicates that the typical chimpanzee's diet, consisting of 75% fruit, leads to a naturally steady dose of alcohol. This corroborates other studies that found similar alcohol consumption behaviors in various species, including fruit flies and elephants. As researchers observe these behaviors, they make connections to human tendencies towards alcohol consumption, revealing deep evolutionary roots and encouraging further exploration into how dietary habits shaped modern alcohol preferences both in humans and other animals.