Royal Society Open Science 2: 150150

Tools to tipple: ethanol ingestion by wild chimpanzees using leaf-sponges

Kimberley J. Hockings, Nicola Bryson-Morrison, Susana Carvalho, Michiko Fujisawa, Tatyana Humle, William C. McGrew, Miho Nakamura, Gaku Ohashi, Yumi Yamanashi, Gen Yamakoshi, Tetsuro Matsuzawa


African apes and humans share a genetic mutation that enables them to effectively metabolize ethanol. However, voluntary ethanol consumption in this evolutionary radiation is documented only in modern humans. Here, we report evidence of the long-term and recurrent ingestion of ethanol from the raffia palm (Raphia hookeri, Arecaceae) by wild chimpanzees (Pan troglodytes verus) at Bossou in Guinea, West Africa, from 1995 to 2012. Chimpanzees at Bossou ingest this alcoholic beverage, often in large quantities, despite an average presence of ethanol of 3.1% alcohol by volume (ABV) and up to 6.9% ABV. Local people tap raffia palms and the sap collects in plastic containers, and chimpanzees use elementary technology - a leafy tool - to obtain this fermenting sap. These data show that ethanol does not act as a deterrent to feeding in this community of wild apes, supporting the idea that the last common ancestor of living African apes and modern humans was not averse to ingesting foods containing ethanol.

Villagers of Bossou tap the raphia palm to gather the sap. The sap then ferments in the collection container. Thus producing palm wine.
Use of leaves for drinking palm wine
PRESS RELEASE: Wild chimpanzees drink alcohol using leafy tools

African apes and humans have recently been found to share a genetic mutation that enables them to effectively metabolise ethanol1. The consumption of ethanol by modern-day humans is nearly universal, being found in every society with fermentable raw materials. However, aside from enforced ingestion in captive experiments or anecdotal observations in wild apes, the habitual and voluntary consumption of ethanol in this evolutionary radiation has been documented until now only in humans. In this research article published in the journal Royal Society Open Science2, a team of International scientists headed by Professor Matsuzawa of the Primate Research Institute at Kyoto University, Japan, provide the first empirical evidence of repeated and long-term ethanol ingestion by any ape in nature. Local people tap raffia palms and the sap collects in plastic containers, fermenting quickly (the sap contained an average presence of alcohol of 3.1% ABV but levels can be as high as 6.9% ABV). Wild chimpanzees at Bossou in Guinea harvest fermented sap from the raffia palm using elementary technology – a leafy tool as a sponge. This absorbent extractive tool was dipped into the small opening of the fermented palm sap container, then retrieved and put into the mouth for drinking. All age and sex classes ingested the fermented palm sap, but some of the chimpanzees consumed high quantities of alcohol. Kimberley Hockings from Oxford Brookes University in the UK and the Centre for Research in Anthropology (CRIA-FCSH/UNL) in Portugal, and lead author of the article said that “some individuals were estimated to have consumed approximately 85ml of alcohol (the equivalent to 8.5 UK units) and displayed behavioural signs of inebriation, including falling asleep shortly after drinking. Our research demonstrates there is not a strict aversion to food containing ethanol in this chimpanzee community.” This ability to use tools may have enabled the last common ancestor of living apes and humans to exploit difficult-to-reach fermented resources.

1 Carrigan MA et al. 2014. Hominids adapted to metabolize ethanol long before human-directed fermentation. Proc. Natl. Acad. Sci. USA. DOI: 10.1073/pnas.1404167111
2 Hockings KJ et al. 2015 Tools to tipple: ethanol ingestion by wild chimpanzees using leaf-sponges. R. Soc. opensci. 2: 150150.


ヒトとアフリカにすむ大型類人猿はアルコール代謝を可能にする遺伝的変異形質を共有している上記1。現代ではほぼ全世界的にアルコールが消費され、どの社会でもアルコールが醸造されていることが知られている。飼育下における実験的投与や野生類人猿における逸話的な観察事例をのぞくと、習慣的かつ自発的なアルコールの消費はこれまでヒトでのみ知られていた。英国王立協会のオープンアクセス誌Royal Society Open Scienceで発表された本研究は、野生類人猿の長期にわたる習慣的なアルコール摂取を定量的に示した初めての報告になる上記2。ギニア共和国ボッソウでは野生チンパンジーの研究が1976年以来、長期に継続しておこなわれている。京都大学霊長類研究所の松沢哲郎教授を研究代表者とし、京都大学や中部大学、オクスフォードブルックス大学、ケンブリッジ大学など国際共同研究チームによる観察データを、筆頭著者のキンバリー・ホッキングス(オクスフォードブルックス大学)が取りまとめた。ボッソウの地域住民はラフィアヤシの木の上にポリタンクを設置し、朝と夕方に自然発酵したパームワインを回収する。アルコール度数は平均すると3.1%だったが、6.9%に至るものもあった。ボッソウにくらす野生チンパンジーは、このポリタンクを発見すると道具となる葉っぱを浸し、パームワインを飲む。1995年から2012年まで計20回、のべ51個体が観察された。この行動は性別を問わず、6歳の子供から大人までにみられた。本研究は、野生チンパンジーがアルコールを含んだものを嫌悪することなく採食することを示している。

Hockings KJ. , Bryson-Morrison N, Carvalho S, Fujisawa M, Humle T, McGrew WC. , Nakamura M, Ohashi G, Yamanashi Y, Yamakoshi G, Matsuzawa T (2015) Tools to tipple: ethanol ingestion by wild chimpanzees using leaf-sponges Royal Society Open Science 2: 150150 , doi: 10.1098/rsos.150150