"Scrumping" apes may explain how humans started drinking alcohol

Walk through any African rainforest at the height of fruit season, and you will eventually stumble upon a surprising scene: apes foraging not in the treetops but on the forest floor, scooping up fallen figs or overripe marulas that have begun to ferment.

Until now, primatologists have documented the behavior but lacked a word that sets it apart from ordinary fruit eating.

A new paper led by Dartmouth College anthropologist Nathaniel Dominy and University of St Andrews primatologist Catherine Hobaiter fixes that linguistic oversight by proposing a single, evocative term – “scrumping.”

“It’s not that primatologists have never seen scrumping – they observe it pretty regularly. But the absence of a word for it has disguised its importance,” Dominy explained.

By naming the habit, the authors hope to inspire more systematic data collection. This simple ground-level snack could hold outsized clues to why human beings tolerate alcohol so well.

A medieval word for a modern puzzle

Scrumping originates from the Middle English rendering of the German “schrimpen.” The word described “shriveled” or “shrunken” fruit that had fallen off the tree. In rural England today, “scrumpy” refers to a rustic cider fermented from windfallen apples.

Dominy and Hobaiter argue that the linguistic lineage is perfect for apes pilfering fermented fruit. Both activities involve the opportunistic gathering of overripe produce with elevated alcohol content.

The name matters because, until now, field notes have lumped floor-foraging events with canopy foraging under the bland heading of “fruit feeding.” That lumping masks the ecological stakes.

Once fruit hits the ground, it becomes a microbial playground where yeasts convert sugars into alcohols. This process often gives the fruit an ethanol punch of a few percent.

For a 220-pound chimp eating ten pounds of such fruit per day, that may add up to a low but steady dose of alcohol. If the capacity to metabolize that ethanol confers a survival advantage, then scrumping could have exerted evolutionary pressure on primate digestive enzymes.

Linking scrumping apes to alcohol genes

In 2015, geneticists reported that the primary enzyme humans use to break down ethanol – ADH4 – underwent a pivotal amino acid tweak in the last common ancestor of humans, chimpanzees and gorillas.

That mutation boosted the enzyme’s efficiency fortyfold. The genetic timeline aligns suspiciously well with fossil and climatic evidence suggesting early apes were spending more time on the ground, perhaps because global cooling was fragmenting forest canopies.

Dominy’s team suspected that scrumping, not tree foraging, was the behavior that turned the genetic key. To test the prevalence of ground-level fruit snacking, they combed through thousands of feeding observations for chimpanzees, western gorillas, mountain gorillas, and orangutans.

Every record pairing ground-level apes with a fruit species normally found higher in the canopy counted as a scrumping event. African apes did it routinely.

Orangutans of Southeast Asia, by contrast, almost never did – and tellingly, the 2015 gene study shows orangutans have a far less efficient version of ADH4.

These weren’t differences of nuance – African apes scrump on a regular basis, but orangutans do not. The contrast strengthens the idea that processing dietary ethanol was an adaptive edge for African lineages.

Escaping competition, avoiding falls

Why would a large ape bother with windfall fruit instead of plucking fresher pieces overhead? Dominy points to two incentives.

First, avoiding the highest branches reduces the risk of potentially fatal falls – a risk he and co-author Luke Fannin quantified in a 2023 study showing that accidents in the canopy exact serious tolls on primate skeletons.

Second, staying on the ground lets apes sidestep competition with smaller, more nimble monkeys that strip trees of unripe fruit. If ethanol metabolism means an ape can safely eat the fermented fare, it gains a foraging niche all its own.

“A fundamental feature of our relationship with alcohol is our tendency to drink together,” said Hobaiter. She wonders whether shared ape scrumping sessions reinforce social bonds in apes the way communal drinking does in humans.

Future fieldwork will track whether group foraging for windfallen fruit correlates with grooming, alliance formation, or mating opportunities.

Happy hour in the jungle

The next empirical frontier is chemistry. Researchers plan to sample ethanol concentrations in fruits still hanging versus fruits lying on the forest floor. They will also monitor ape breath or urine for ethanol metabolites to estimate intake more precisely.

If chronic low-level exposure proves common, it could reshape narratives about ancient hominin diets and even the timing of the agricultural revolution, when humans began deliberately fermenting grains and grapes.

“Scrumping by the last common ancestor of gorillas, chimpanzees, and humans about 10 million years ago could explain why humans are so astoundingly good at digesting alcohol,” Dominy noted.

He suggests that long before our ancestors brewed beer, natural selection had already equipped them with biochemical bar tabs.

Will scrumping stick?

Scientific neologisms catch on only if they fill a conceptual gap – think “symbiosis” in the 19th century or Richard Dawkins’s “meme” in 1976. Dominy believes scrumping meets that test.

It instantly conveys a specific behavior – ground foraging for fermented fruit – that generic terms cannot. If colleagues adopt the label, datasets will soon be searchable, hypotheses testable, and evolutionary stories clearer.

“We never knew we needed the word until we did. That’s natural selection at work,” Dominy said. Whether scrumping becomes a staple of primatology vocabulary remains to be seen.

But the paper makes a compelling case: name the behavior, and the science of why we drink – and how we evolved – may gain a fresh ferment of insight.

The study is published in the journal BioScience.

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