A close look at monkeys from whom humankind has evolved suggests that the love of people for alcohol stems from the liking these primates have for fruits which are ripe, states sciencealert.com report.
Scientists discovered during their study of Panama’s black-handed spider monkeys or Ateles geoffroyi that they eat on a regular basis palm fruits that have ethanol in little amounts. Further, the samples of urine from two monkeys showed metabolites that were ethanol specific, thus proving that it was being absorbed and used by the body.
Talking about this, Christina Campbell from California State University, Northridge, who is a primatologist said: "For the first time, we have been able to show, without a shadow of a doubt, that wild primates, with no human interference, consume fruit containing ethanol. This is just one study, and more need to be done, but it looks like there may be some truth to that 'drunken monkey' hypothesis."
Proposed for the first time in 2000 by Robert Dudley, a UC Berkeley biologist the drunken monkey hypothesis stated that monkeys exhibited a powerful allure for the aroma and taste of ethanol which worked out advantageous for them from evolutionary perspective as it enabled them reach and eat ripe fruits which were full of energy much before others could.
While the same yearning for the ethanol is present among human beings, it is devoid from the nutritional benefits the whole fruit affords. By distilling the spirits, “the once advantageous appetite for alcohol" among human ancestors – the primates – has become a hazard for the health and happiness of people.
In the past too, there have been instances of monkeys’ affinity for alcohol. Wild chimpanzees or Pan troglodytes have been seen devouring fermented sap from palm trees – have ethanol concentrations of seven per cent. It was not explicit if the creatures were lured to the fruit by the ethanol or if they were really getting drunk.
The Panama study is the first of its kind that measures directly the eating of alcohol-heavy fruits by the monkeys that too in the wild while in captivity, these animals have shown their partiality to ripe fruits.
It is not just consuming but also digesting the fermented sugars by the monkeys that is vital. Campbell observed: “The monkeys were likely eating the fruit with ethanol for the calories. They would get more calories from fermented fruit than they would from unfermented fruit. The higher calories mean more energy."
What works for the animals does the same for the human beings as the same fruits eaten lovingly by spider monkeys are made use of by the indigenous people of Central and South America to prepare chicha – a alcoholic beverage that is fermented.
People who eat fruit which is highly fermented, get more energy but also probably become more drunk. Yet, the spider monkeys there are hardly any inebriation. Analysis of partially eaten fruits by the monkeys shows one or two per cent of ethanol.
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Elaborating on this Dudley remarked: "They're probably not getting drunk, because their guts are filling before they reach inebriating levels. But it is providing some physiological benefit. Maybe, also, there's an anti-microbial benefit within the food that they're consuming, or the activity of the yeast and the microbes may be predigesting the fruit. You can't rule that out."
The evolutionary advantage of alcohol which has been passed down for millions of years from the common ancestors of human beings and modern primates is evident in DNA. The ethanol metabolism genes are encoded widely among mammals who consume nectar and fruit and gorillas, bonobos, chimpanzees and humans all have gene mutation that improves an ethanol enzyme by 40 times.
The study’s authors in conclusion stated: "Given that positive selection on those genes encoding for ethanol catabolism has been substantial among fruit- and nectar-consuming mammalian species more generally, the natural consumption of fermented carbohydrates is likely to be more widespread than is currently realized.”
Details of the research were published in Royal Society Open Science.
