Book: Drunken monkey

There may be evolutionary reasons we are attracted to alcohol according to a new thesis. Reviewed by Bill Condie.

Male fruit flies deprived of mating opportunities show an increased preference for alcohol. In fact fruit flies, even when not lovelorn, are eager to hit the bottle. In laboratory conditions, Robert Dudley tells us, they will always opt for fruit pulp that has been supplemented with alcohol.

There are evolutionary reasons for this behaviour. And, indeed, for problem drinking among humans, Dudley argues, as he struggles to understand the root causes of alcoholism – a disease which killed his father.

Fruit flies are hardwired to seek out fermenting fruits. The scent of alcohol reliably indicates to them a suitable sugar and yeast-rich environment on which to feed and lay eggs. Other animals, including apes and us, may be driven in part by similar considerations – a direct link from fruit fly to bar fly.

Dudley, Professor of Integrative Biology at the University of California, Berkeley, believes that our attraction to alcohol comes from its association with food. He argues that its origins lie with the primates that evolved as fruit-eaters in tropical jungles. The potent smell of fermentation was a sure way to find a food source, as well as a ripeness indicator.

There may also be an “aperitif effect” where alcohol in small doses increases appetite, allowing greater consumption of food when it is abundant.

Problems occur when alcohol becomes amply available in high concentrations.

So if that’s the case, why is it only humans who routinely overdo it? Mostly it's lack of opportunity. Other animals seldom get rolling drunk for the simple reason fermenting fruit contains alcohol in such low concentrations that an ape will have eaten all it can long before it has ingested enough alcohol to become intoxicated.

Problems occur when alcohol becomes amply available in high concentrations. In this, Dudley says, there are parallels to the causes of the obesity and diabetes epidemics in the developed world, which he describes as “a compelling testimony both to the efficiency of modern food production and our intrinsic behavioural reactions to cheap food”. In short, if food – or booze – is cheap and plentiful, we tend to consume too much of it.

Dudley freely admits there is still too little data to provide definitive conclusions to his hypothesis. Most information comes from experiments with tipsy fruit flies and they can only tell us so much. In order to come up with better understanding of, and more effective treatments for problem drinking, he wants to see an interdisciplinary approach with behavioural biologists, evolutionary biologists and geneticists.

“We owe it to the sufferers of alcoholism, and to those who indirectly endure the outcomes of this disease to pursue these questions further,” he says.

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