Spider monkey habits reveal why humans started drinking alcohol

A group of golden spider monkeys’ preference for overripe palm fruit may explain how humans got into drinking alcohol thousands of years ago.

Countless studies have demonstrated how alcohol intake affects our brains and bodies. Yet alcohol consumption remains a deeply rooted part of human culture – and has been so for thousands of years. But why are we so keen on fermented liquids? A team of scientists may have found the answer – in a group of golden spider monkeys from Panama’s tropical rainforest.

By monitoring the monkeys’ food consumption over a long period of time, the scientists discovered that the monkeys feast on fermented palm fruit on a daily basis. The fruit has a low content of ethanol, and the scientists found substances from the breakdown of alcohol in the monkeys’ urine. This revealed that the alcohol from the fermented fruit is absorbed and used in the monkeys’ bodies – it does not simply pass through the system.

According to the scientists, the new study is the first to prove that the monkeys frequently absorb alcohol without any human interference. Monkeys feed on the fermented palm fruit because it includes more calories and so more energy than the unfermented version, they suggest.

The discovery in the Panamanian forest revives an old hypothesis known as the drunken monkey hypothesis. The theory, first introduced by biologist Robert Dudley in 2000, suggests that the attraction of primates to both the smell and taste of ethanol could provide an evolutionary advantage that makes it easier to identify the mature and high-energy fruit before other animals take it. According to this hypothesis, this attraction was inherited through our own species’ DNA and still thrives – although we now have the option of alcohol with or without the calorific advantages of the overripe fruit.