Chimps imbibe two cocktails’ worth of ethanol daily from ripe fruits

IN NEWS:

Chimpanzees imbibe two cocktails’ worth of ethanol daily from ripe fruits – The Hindu, October 22, 2025

UPSC STYLE ANALYSIS

1. Context:

A new study by researchers from the University of California (UC) Berkeley, published in Science Advances (2025), found that wild chimpanzees consume naturally fermented ripe fruits containing ethanol — equivalent to one or two glasses of wine daily. The study supports the “Drunken Monkey Hypothesis”, which links alcohol preference in humans to evolutionary adaptations shared with primates.

2. Key Findings of the Study:

• Ethanol Presence: Ripe fruits eaten by chimpanzees naturally contain less than 1% alcohol due to fermentation by yeast.
• Daily Intake: On average, chimpanzees consume around 14 grams of ethanol per day, equivalent to one standard American drink.
• Body Weight Adjustment: Considering their body weight (~40 kg), this equals nearly two drinks for a human.
• Diet Composition: About 75% of their diet consists of ripe fruits (~4.5 kg/day).
• Preferred Fruits: Sticky figs (Ficus mucuso, Ficus sur) are particularly high in natural ethanol content.
• Behavioral Observation: Despite regular intake, chimps showed no visible intoxication since the alcohol is consumed gradually through the day.

3. Evolutionary Significance:

• The study provides evidence for the “Drunken Monkey Hypothesis” (Robert Dudley, 2014), which posits that early primates evolved an attraction to ethanol as a cue for ripe, calorie-rich fruits.
• Such exposure may have led to genetic adaptations for ethanol metabolism in the primate lineage.
• Supporting studies (Matthew Carrigan, College of Central Florida) indicate a genetic mutation around 10 million years ago that increased ethanol metabolism by 40-fold in the last common ancestor of African apes and humans.
• Observations from Cantanhez National Park (Guinea-Bissau) also show chimpanzees using tools to access fermented palm wine, implying an evolved tolerance and attraction to ethanol.

4. Research Locations:

• Ngogo, Kibale National Park – Uganda
• Taï National Park – Côte d’Ivoire

5. Broader Implications:

• Highlights biological and evolutionary roots of human alcohol preference.
• Contributes to understanding animal behavioral ecology and metabolic adaptations.
• Demonstrates how natural fermentation processes influence feeding behavior in wild species.

STATIC PART

• Species Studied: Pan troglodytes (Chimpanzee)
• Closest Human Relative: Shares 98.8% DNA similarity with humans.
• Fermentation Mechanism: Natural yeast converts fruit sugars into ethanol during ripening.
• Alcohol Concentration: Less than 1% ethanol in ripe fruits.
• Scientific Terms:
  • Ethanol metabolism
  • Fermentation by yeast (Saccharomyces spp.)
  • Evolutionary physiology
  • Behavioral ecology
    
    Updated - October 22, 2025 06:30 am | The Hindu