CALGARY -- A study looking at the effect of fermented fruit on large mammals like elephants may sound silly, but researchers at the University of Calgary say it's taught them some important lessons about metabolism and alcoholism in humans.
The paper, published in Biology Letters, has debunked the myth that large mammals such as elephants can't become intoxicated after eating quantities of rotting fruit.
It was previously thought, even among scientists, that wildlife would need to eat enormous amounts of the material to become "drunk." However, a closer look has proven that's not the case.
Dr. Amanda Melin, along with members of her Primate Genomics and Ecology Lab, has found that humans have evolved an ability to metabolize ethanol much quicker than other mammals.
"Humans have a change in one of their alcohol dehydrogenase proteins (alcohol dehydrogenase class 4, which is encoded by the gene ADH7) that makes it 40x faster at metabolizing ethanol. This change evolved around 10 million years ago in our common ancestor with chimpanzees and gorillas, presumably as an adaptation for a fruit diet," the U of C said in a release.
This modified protein is something that most other mammals do not possess, says Dr. Mareike Janiak, lead author on the study.
"Many mammals didn’t even have a functional ADH7 gene, including African and Asian elephants. While they might have other ways of metabolizing ethanol, the lack of a functional alcohol dehydrogenase class 4 definitely suggests that their ability to do so is very different from that of humans."
She says the myth about larger animals, like elephants and moose, being able to prevent themselves from becoming intoxicated, merely came from their large body size. This new knowledge has now done away with that assumption.
"Ethanol is common in ripe fruits and nectars, especially among those fallen to the forest floor. Our study finds that mammals that do not consume fruits and nectars are more likely to have lost the gene for metabolizing natural alcohols," Janiak says.
Researchers say the study has helped them with more than just dispelling a common myth about elephants. It's also taught them something that could help in future studies focusing on alcoholism in humans.
"We often assume that other animals share our digestive adaptations, but that may not be the case," Janiak says. "Humans are unique among mammals in being able to digest lactose, the main sugar in milk, as adults, for example. Likewise, mice cannot metabolize ethanol the same way that humans can, which could have implications for how research findings translate to humans."
