Our relationship with alcohol is quite complex. While it can serve as a social lubricant or help some individuals relax, excessive intake can lead to addiction and cause various health problems. Alcohol occurs naturally as a byproduct of fermenting sugary fruits and nectars, which is why several animals — including insects, monkeys, bats, and even elephants — are known to intentionally seek out fermented fruits for their alcohol content. Researchers are fascinated by why some animals can’t resist the pull of alcohol and how it might aid them in other ways.

Fruit flies (Drosophila melanogaster) are especially attracted to the smell of fermenting fruit, often swarming our kitchens during warmer months. D. melanogaster is a commonly used model organism in many fields of research due to its small size, rapid reproduction, and the overlap with the human genome, making them easy to handle while providing meaningful results.

A research team from the Departments of Evolutionary Neuroethology and Insect Symbiosis, along with the Olfactory Coding Research Group at the Max Planck Institute for Chemical Ecology, suggests that alcohol significantly impacts mating processes, broadening our understanding of alcohol use across the animal kingdom. The recent study was published in Science Advances.

Coping with Alcohol Consumption

Previous research has explored why adult fruit flies and larvae are so drawn to alcohol in fermenting fruits. They discovered that virgin males are more attracted to alcohol than males who have recently mated. Researchers also found a neural connection between alcohol consumption and reward pathways in the brain, leading them to propose that virgin D. melanogaster males might use alcohol to cope with sexual rejection by females.

This hypothesis has led to a fascinating insight: there are similar genetic pathways in the human brain related to alcohol consumption. This discovery could inform new strategies for addressing drug abuse, addiction, and other neurological conditions.

Read More: Drinking Alcohol May Increase Your Risk of Some Cancers

Alcohol Risk and Reward

The new study tests a theory that fruit flies seek alcohol not to deal with rejection, but to increase their chances of mating.

“In our experiments, we show a direct and positive effect of alcohol consumption on the mating success of male flies. The effect is caused by the fact that alcohol, especially methanol, increases the production of sex pheromones. This in turn makes alcoholic males more attractive to females and ensures a higher mating success rate, whereas the success of drunken male humans with females is likely to be questionable,” said first author of the study Ian Keesey, in a press release.

Additionally, they found that methanol — the alcohol that most boosts mating success — is also deadly in high concentrations. As a result, male flies must decide how much exposure to methanol is necessary to enhance their mating chances without causing harm. Neurophysiological studies revealed three neural circuits that maintain a balance between attraction and aversion, providing D. melanogaster with an impressive control mechanism.

“That different neural pathways with opposite responses to the same odor are combined to balance attraction and aversion based on physiological state is a rarity,” Keesey said in the release.

Evolving With Their Alcoholic Environment

In the evolutionary battle for mates, outcompeting rival males is a key factor in reproduction. For a species that has evolved over millions of years to coexist with its preferred, microbe-rich, alcoholic environments, it’s only natural that females would select males based on how well they interact with this environment.

“The study provides one of the first comprehensive explanations of alcohol attraction in a model organism, from chemistry to ecology, and from brain to behavior and vice versa. It also emphasizes the importance of considering the natural behavior and ecology of animal models when using them to study physiological and behavioral processes,” said Bill Hansson, head of the Department of Evolutionary Neuroethology at the Max Planck Institute, in the news release.

Read More: What Are Short and Long Term Effects of Alcohol On the Brain?

Article Sources

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Having worked as a biomedical research assistant in labs across three countries, Jenny excels at translating complex scientific concepts – ranging from medical breakthroughs and pharmacological discoveries to the latest in nutrition – into engaging, accessible content. Her interests extend to topics such as human evolution, psychology, and quirky animal stories. When she’s not immersed in a popular science book, you’ll find her catching waves or cruising around Vancouver Island on her longboard.