Rosa Rubicondior: Creationism Refuted - Common Origins of Alcohol Metabolism In Humans And African Apes

Saturday, 2 August 2025

Creationism Refuted - Common Origins of Alcohol Metabolism In Humans And African Apes

Scrumped fruit key to chimpanzee life and a major force of human evolution | University of St Andrews news

(b) Scrumping of Pentadesma butyracea (Clusiaceae) by a western gorilla.

Photograph: MMR.

Photograph: CH.

The human ability to consume and metabolise alcohol efficiently may trace back to our ape ancestors, who regularly ate overripe and fermented fruit with a naturally high alcohol content. This is according to researchers from the University of St Andrews, Scotland, and Dartmouth College, USA.

The bad news for creationists is that this discovery strongly supports the common ancestry of modern apes and humans. The researchers are in no doubt that the Theory of Evolution explains the presence of the same genetic mutation in African apes — including humans — which allows us to metabolise alcohol around 40 times more efficiently than orangutans, which lack the mutation.

This mutation enables African apes to consume fermented fruit — often as a social activity — in a pattern of alcohol consumption strikingly similar to that seen in humans.

To describe this behaviour in wild chimpanzees, the researchers have borrowed the term scrumping — a familiar UK English word for the (often illicit) picking and eating of apples, particularly by children. The word derives from the Middle Low German schrimpen, meaning ‘shrivelled or shrunken’ (to describe over-ripe fruit). It also survives in the name of the traditional West Country cider known as scrumpy.

What information do you have on the ADH4 enzyme and the mutation that enabled more efficient alcohol metabolism? The enzyme in question is alcohol dehydrogenase 4 (ADH4), which plays a key role in the metabolism of ethanol (alcohol) in primates and other mammals.

Overview of ADH4:

Function: ADH4 is part of a family of alcohol dehydrogenases, which convert ethanol into acetaldehyde — a toxic intermediate that is later broken down into acetate by other enzymes like ALDH2.
Location: It is primarily expressed in the stomach and upper gastrointestinal tract, where it contributes to the first-pass metabolism of alcohol before it enters the bloodstream.

The Key Mutation:

A single amino acid change in the ADH4 gene significantly increased the enzyme’s ability to metabolise ethanol.

The mutation: The critical evolutionary change is a replacement of alanine with valine at position 294 (A294V) in the ADH4 enzyme.
Effect: This change boosted the enzyme's catalytic efficiency towards ethanol by a factor of about 40 times, compared to the ancestral form found in earlier primates and in modern orangutans.
Timing: Molecular clock studies suggest that this mutation appeared around 10 million years ago, coinciding with a time when the common ancestor of African great apes (chimpanzees, gorillas, humans) had likely become more terrestrial — and thus more likely to encounter fallen, fermented fruit on the forest floor.

Evolutionary Context:

Fruit fermentation: Ethanol naturally occurs in rotting fruit due to yeast fermentation. Foraging apes would encounter low levels of alcohol in such fruit regularly.
Selective advantage: Apes with a more active ADH4 enzyme could safely consume mildly fermented fruit without suffering the intoxicating or toxic effects of ethanol, gaining access to a calorie-rich food source.
Species differences:

Orangutans, which remain largely arboreal and less exposed to fallen fruit, retain the ancestral version of ADH4 and show much lower ethanol metabolism efficiency.
African apes and humans share the derived A294V variant, suggesting it evolved after the orangutan lineage split off but before humans, chimpanzees, and gorillas diverged from each other.

Key References:

Carrigan, M. A. et al. (2015). Hominids adapted to metabolize ethanol long before human-directed fermentation. PNAS, 112(2), 458–463. DOI: 10.1073/pnas.1404167111.

This is the landmark study that identified the A294V mutation and explored its evolutionary implications.

St Andrews & Dartmouth (2024). Scrumped fruit key to chimpanzee life and a major force of human evolution. University of St Andrews press release.

Link to article.

Implications:

This mutation is a textbook example of adaptive evolution in response to dietary pressures.
It provides strong molecular evidence of common ancestry among African apes and humans.
It undermines creationist claims of human uniqueness or sudden creation, as it demonstrates a gradual adaptation shared with other primates.

The researchers have published their findings open-access in the journal BioScience, and a lay summary can be found in this St Andrews University press release.

Scrumped fruit key to chimpanzee life and a major force of human evolution
New research from the University of St Andrews and Dartmouth College examines the crucial, but until now, overlooked, role of ‘scrumped’ fruit in the lives of great apes and the origins of human feasting.
Published in BioScience, this pioneering study is the first to tackle the mystery of why humans are so astoundingly good at metabolising alcohol.

The findings show that feeding on fermented fruits gathered from the forest floor is an important behaviour in the lives of African apes, and one that explains why they, and we, evolved the ability to digest alcohol efficiently.

Researchers from the University of St Andrews and four other international institutions worked with a large observational data set to quantify, for the first time, how regularly this behaviour happens across great apes.

One problem for the researchers was that there was no word to describe ‘feeding on fruits gathered from the forest floor.’ Nobody wants more jargon, but without a word to talk about something, a behaviour is easily overlooked.

They repurposed the word ‘scrumping’, the act of gathering, or sometimes stealing, windfallen apples and other fruit. It is an English derivation of the middle low German word schrimpen, a mediaeval noun for describing overripe or fermented fruit.

Whilst searching for the right term they discovered that there is a long-standing representation in gothic art of primates picking fruit from the ground. By repurposing the term scrumping, they suggest their work is a case of “life imitating art imitating life.”

A range of work points towards the fact that ripe fruit contain small-but scrumptious-levels of ethanol, there have been recent findings hinting at the importance of chimpanzees’ feeding socially on fruits.

Building on those findings, this paper has revealed that, counter to widespread beliefs that primates do not ‘scrump,’ African apes, but not orangutans, ‘scrump’ on a regular basis. This behavioural difference is crucial, as the same pattern is reflected in an important genetic mutation that allows African apes to metabolise alcohol 40x more efficiently than orangutans and other primates, and could be an important link to the evolution of humans’ long-standing affair with alcohol.

A fundamental feature of our relationship with alcohol, is our tendency to drink together, whether a pint with friends or a large social feast. The next step is to investigate how shared feeding on fermented fruits might also influence social relationships in other apes.

One upshot is that sharing a cold pint of scrumpy this summer echoes a behaviour our ape ancestors might have already been partaking in 10 million years ago.

Professor Catherine Hobaiter, co-lead author
School of Psychology and Neuroscience
University of St Andrews
St Andrews, Scotland, UK.

Publication:

Nathaniel J Dominy, Luke D Fannin, Erin R Vogel, Martha M Robbins, Catherine Hobaiter,
Fermented fruits: scrumping, sharing, and the origin of feasting, BioScience, 2025;, biaf102, https://doi.org/10.1093/biosci/biaf102

Abstract
Mounting evidence points to the importance of fermented fruits in the diets of tropical frugivores, especially African apes. But how has this fundamental aspect of ape ecology escaped scientific attention over the past six decades? Here we draw inspiration from the Middle Ages to fill an essential void in scientific discourse.

The quality, availability, and accessibility of fruit are integral to almost every aspect of ape biology and behavior, and it is practically axiomatic to describe apes as frugivores. It is a classification that rings true even when fruit is scarce, because all apes show a categorical preference for ripening fruit when available, a behavior that holds renewed significance in light of a recent review by Bowland et al. (2025a). Their work puts a spotlight on the underrecognized role of dietary ethanol as a selective force on tropical frugivores, and it shows that most ripening fruit is fermented to some degree. Welcome and timely, their paper raises tantalizing questions on the ethanol content and ecology of fallen fruits, a topic with special relevance for human evolution (Dudley and Maro 2021).

Carrigan et al. (2015) drew attention to fallen fruits in the diets of African apes. Their study reported the protein sequences and corresponding kinetic activities of alcohol dehydrogenase class IV (ADH4), the first enzyme to encounter and metabolize dietary ethanol. They sequenced the genes of 18 primate species and resurrected nine ancestral proteins to trace the evolution and functional ecology of ADH4. This innovative approach produced two important findings. First, the ADH4 enzymes of most primates are essentially inactive against ethanol. Second, a single amino acid change (A294V) in the gene of the last common ancestor of African apes accounts for a dramatic fortyfold increase in ethanol-catalyzing activity. The significance of this mutation is rather profound, representing, potentially, a signal moment in the history of life on Earth. If the early domestication of cereals revolved around making beer instead of bread, then the A294V mutation was the preadaptation that fueled the Neolithic Revolution and everything that followed (Dominy 2015.1).

Happy hour
To explain the retention of this mutation, Carrigan et al. (2015) argued that increasing terrestrialism during the Middle Miocene exposed the ancestor of crown African apes to “overripe [fermented] fruit that [had] fallen to the ground” (p. 461). It is a compelling idea that suffers from two problems: the ethanol exposure of African apes is all but unknown, and primatologists seldom differentiate fallen fruits from arborescent ones in their field notes, meaning we have little sense of how often apes consume fruits from the ground. In fact, we don't even have a word for this behavior.

The history of ideas is paved by constraints of language

Leo W. Bus, The Evolution of Individuality (1988).
Nobody wants more jargon, but sometimes we need a new word, or neologism, to capture a fundamental concept. Albert Bernhard Frank coined the word symbiosis in 1877 to describe the astonishing mutualisms of lichens (Martin and Schwab 2012), and it is difficult to imagine pop culture today without the word meme, a gift of Richard Dawkins in 1976 (Dawkins 1976). In primatology, we didn't know how much we needed the word cathemeral (to describe the arrhythmic activity patterns of some lemurs) until lan Tattersall invented it in 1988 (Tattersall 2006). New words can propel scientific discourse and discovery, and we wondered whether progress on the topic of fruit–animal interactions has been stymied for want of language. So we puzzled over how to reduce consumption-of-fallen-fruit into a single practical word.

Scrumping
Scrumping is the act of gathering — or sometimes stealing — windfallen apples and other fruit. It is an English derivation of the Middle Low German word schrimpen (“shrivelled, shrunken”), a medieval noun for describing overripe or fermented fruit. It is an obscure origin perhaps, but its legacy echoes in many British pubs today, where patrons can order scrumpy, a cloudy apple cider with an alcohol by volume (ABV) content that ranges between 6 and 9%. The adjective scrumptious (something delicious, alluring) alludes to fruit and temptation, a frequent motif in Gothic art and architecture. Indeed, the Gothic tradition recognized scrumping as an essential behavior of nonhuman primates (box 1).

Box 1. Scrumping monkeys in the Garden of Eden

Gothic monkeys as the embodiment of curiosity and temptation. Top left: a column statue, Cathédrale de Chartres. At left, Fortitude stabs a lion (inscription crudelitas, “cruelty”); at right, Justice conquers a monkey (inscription curiositas, “curiosity”). Photograph: Jane Vadnal, reproduced with permission. Bottom left: a bronze plaquette with gilding titled Adam and Eve, dated 1514 by Ludwig Krug. Photograph: Hood Museum of Art, Dartmouth College, reproduced with permission. Right: panel painting titled Earthly Paradise with the Fall of Man, dated 1615 by Peter Paul Rubens (the figures) and Jan Brueghel the Elder (the flora and fauna, including two monkeys resembling Cercocebus torquatus on the left and Cercopithecus petaurista on the right). Photograph reproduced under CC0 1.0 license.

Lustful, fruit-eating monkeys were an influential motif during the Middle Ages. Their origin can be traced to twelfth century bestiaries and the Mater Verborum, an encyclopaedic dictionary. Both works featured monkeys handling fruit, a Biblical symbol of temptation. By 1499, this iconography expanded to include Eve, who appeared, alongside a fruit-eating monkey, in the Bible Historiee by Antoine Verard. The original woodcut was recycled in the illustrations of many subsequent publications—including this paragraph—effectively cementing monkeys in the Gothic tradition, and becoming a fixture in the Fall of Man, a Christian doctrine that describes the human transition from a state of innocence to one of disobedience and sin.

But how did monkeys come to symbolize temptation? Curiosity is the essential ingredient of temptation, a connection exemplified in a twelfth century sculptural decoration of Virtues and Vices at Chartres Cathedral. Curiosity was an established vice in Early Christian theology, sometimes represented as the lowest step on the ladder of Pride. The art historian Horst Janson argued that monkeys were innately curious objects of curiosity, a combination of traits that was simultaneously fascinating and repulsive. This dual meaning of curiosity could partly explain how scrumping monkeys became a visual allegory. They embody the transition between innocence and sin.

Exemplary masterworks include Adam and Eve by Ludwig Krug in 1514 and Earthly Paradise with the Fall of Man by Rubens and Brueghel in ca. 1615. Both works create a strong contrast between scrumping monkeys and the crafty serpent. Monkeys are never malicious; they exist as a visual metaphor for curiosity, temptation, and sin, the same traits that led to Adam's undoing. Janson (1952) put it this way, “[fruit-eating monkeys] are a projection of man's own weakness” (p. 133). The Irish humourist Oscar Wilde is noted for saying, “life imitates art far more than art imitates life.” Epitomizing this view is the word thagomizer (the caudal spikes of stegosaurid dinosaurs), which cartoonist Gary Larson coined in 1982. It is now widespread in the scientific literature. The present use of scrumping, however, is a case of life imitating art imitating life.
Equipped with this word, we were curious to quantify the frequency of scrumping among great apes. We surveyed dietary reports for orangutans (Pongo pygmaeus), western gorillas (Gorilla gorilla), mountain gorillas (Gorilla beringei), and chimpanzees (Pan troglodytes), cross-referencing fruit-feeding observations with the vertical height of the focal animal or group. If a given fruit develops in the middle or upper canopy levels, and if feeding occurred at ground level (0 meters), then we classified the behavior as scrumping. This exercise revealed divergent patterns, with broadly comparable levels of frugivory obscuring stark differences in scrumping (figure 1a). African apes are regular scrumpers, bolstering Carrigan and colleagues’ (2015) hypothesis, but we don't know if it exposes them to meaningful levels of ethanol, as was predicted by Bowland et al. (2025a). It is an empirical question that commands attention.

Figure 1. The (a) frequency of frugivory is broadly comparable across studies of orangutans (Pongo pygmaeus wurmbii; Vogel et al. 2015.2; n = 5553 hours of fruit-feeding), western gorillas (Gorilla gorilla gorilla; Robbins et al. 2022; n = 16,696 scans of fruit-feeding), and eastern chimpanzees (Pan troglodytes schweinfurthii; Villioth et al. 2023; n = 638 hours of fruit-feeding), and it remains important, if less so, for mountain gorillas (Gorilla beringei beringei; Ostofsky and Robbins 2020; n = 25,590 scans of fruit-feeding), but this traditional approach to quantifying diet obscures striking differences in fruit-feeding at arborescent heights versus ground level, or scrumping. Drawing attention to this distinction highlights the importance of scrumping to African apes, species that share the A294V mutation of ADH7 (also referred to as ADH4), the gene that encodes the alcohol dehydrogenase class IV (ADH4) enzyme (Pinto et al. 2023.1). This single amino acid change accounts for a fortyfold increase in catalytic efficiency. (b) Scrumping of Pentadesma butyracea (Clusiaceae) by a western gorilla; photograph: MMR. (c) Scrumping of Gambeya albida (syn. Chrysophyllum albidum; Sapotaceae) by an eastern chimpanzee; photograph: CH.

Nathaniel J Dominy, Luke D Fannin, Erin R Vogel, Martha M Robbins, Catherine Hobaiter,
Fermented fruits: scrumping, sharing, and the origin of feasting, BioScience, 2025;, biaf102, https://doi.org/10.1093/biosci/biaf102

Copyright: © 2025 The authors.
Published by Oxford University Press on behalf of the American Institute of Biological Sciences. Open access.
Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)

This discovery presents yet another challenge for creationists, as it highlights a clear, testable example of adaptive evolution shared by humans and our closest primate relatives. The mutation in the *ADH4* gene, which enhances alcohol metabolism by around 40-fold, is found in humans, chimpanzees, and gorillas, but not in orangutans or more distantly related primates. This precise pattern of inheritance is exactly what we would expect from common ancestry, with the mutation arising in the lineage leading to African great apes after their divergence from the orangutan line some 10 million years ago.

From an evolutionary perspective, the mutation provided a selective advantage to ground-dwelling apes who frequently encountered fermented fruit on the forest floor. Those with a more efficient ability to metabolise ethanol could exploit this rich food source without the toxic effects of alcohol, leading to increased survival and reproductive success. Crucially, this is not a trait designed for humans alone, nor one that suddenly appeared; it is part of a gradual, observable process that neatly fits the evolutionary timeline.

For creationists, this poses a serious problem. There is no credible creationist model that can account for why African apes and humans share this specific mutation, while orangutans and other primates do not. Invoking separate creation events would require an ad hoc explanation for why a shared, functionally significant mutation appears only in a subset of species with a well-documented evolutionary relationship. As with so many other lines of evidence — from endogenous retroviruses to pseudogenes and anatomical vestiges — the evolution of alcohol metabolism in apes reinforces the robust, predictive power of evolutionary theory and further undermines any notion of special creation.

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