Chimps consume equivalent of a beer a day in alcohol from fermented fruit

"The apes were particularly fond of figs, which contained some of the highest levels of alcohol the team recorded. Aleksey Maro, a graduate student at the University of California, Berkeley, said at both African sites, males and females consumed about 14g of pure ethanol per day through fermented fruit. That is equivalent to one standard US drink or half a pint of 5% ABV lager."

"The chimps are eating 5 to 10% of their body weight a day in ripe fruit, so even low concentrations yield a high daily total, a substantial dosage of alcohol, said Prof Robert Dudley, also at UC Berkeley. Dudley believes the chimps' consumption of alcohol in the wild supports his drunken monkey hypothesis, which posits that the human penchant for drink has roots in our primate ancestors' need for energy-rich, ripe, fermented fruit."

Ethanol levels were measured in fallen, fermented fruit in Kibale (Uganda) and Tai (Ivory Coast) to estimate wild chimpanzee alcohol intake. Individual fruits often contained under 0.5% alcohol, but chimps consume 5–10% of their body weight daily in ripe fruit, producing substantial cumulative ethanol intake. Figs showed some of the highest alcohol concentrations and contributed to daily totals. Male and female chimpanzees at both sites averaged about 14 g of pure ethanol per day, equivalent to a half pint of 5% lager. This consumption aligns with the idea that attraction to alcohol may originate from ancestral foraging on fermented, energy-rich fruit.

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