Study sheds new light on the origins of humans drinking alcohol.
While we may turn into “animals” when we tipple a bit too much tequila, alcohol is actually a natural part of many primates’ diets. Found in fermented nectars, saps and fruits, over the ages primates have evolved to digest alcohol quickly and to minimize its toxic effects.
With previous research suggesting that primates may employ alcohol for its calories, scientists at Dartmouth wanted to see if the same appeal held true for aye-ayes (pictured above) – a wonderfully, awesomely odd prosimian endemic to Madagascar. These nocturnal lemurs date back nearly 70 million years; they sport an elongated, craggy finger for digging out grubs from decaying tree trunks. And as it turns out, when given the choice, they’ll opt for boozy quaffs over virgin ones.
"Aye-ayes are essentially primate woodpeckers," says Nathaniel J. Dominy, a professor at Dartmouth and an author of the new research. "So it is puzzling that they can digest alcohol so efficiently."
In the study, the team of researchers set out to find if, like their primate cousins, aye-ayes are attracted to alcohol. They discovered that both aye-ayes and another prosimian primate, a slow loris (pictured below), “could discriminate different concentrations of alcohol, and further, that each species preferred the highest concentrations of alcohol available to them.”
The team worked with two aye-ayes, Morticia and Merlin, and a slow loris, Dharma, to see if the animals were attracted to or averse to varying concentrations of alcohol in simulated nectar.
Each liquid treatment, together with two controls, was placed in a circular array of small-recessed containers in a round resin outdoor table. The position of the liquids was randomized and behavioral data were collected blind to the contents, to avoid observational bias.
They found that the aye-ayes could totally tell the difference between water and the spiked drinks, and they drank accordingly. The aye-ayes preferred the highest concentrations of alcohol.
"Unexpectedly, the aye-ayes continued to probe the containers with the highest concentrations long after they were emptied, suggesting that they wanted more," the authors note.
While the team didn’t conduct enough tests with the slow loris to arrive at a statistical conclusion, they say that the pattern of discrimination and preference was practically identical to that of the aye-ayes.
"This project has definitely fueled my interest in human evolution," says researcher Samuel Gochman. "Our results support the idea that fermented foods were important in the diets of our ancestors."
It’s possible that humans’ genetic mutation to efficiently digest alcohol is linked to the consumption of fermented fruits on the forest floor, note the scientists, a dietary behavior that could have pre-adapted humans for the Neolithic Revolution. Not to mention happy hour.