By Noah Kaufman
Updated October 16, 2014
© Pinhole Photographic / Stockimo / Alamy

Here’s an excuse to start happy hour really early today: Conduct an educational experiment. Grab a beer and take a good whiff. You have brewer’s yeast to thank for the wonderful ripe fruit and floral aromas indicative of an expert beer. But now, scientists have delved deeper into why our beer smells so good. The answer is fruit flies.

After discovering an escaped colony feasting on an exposed yeast culture, scientists at the Belgian research institute VIB spent years trying to explain what brings all the flies to the yeast. Their just published study reveals a lovely co-evolution of two species. It’s easy to forget that yeasts are living organisms, and as such, they have evolved over time. One of those evolutionary changes was to help attract fruit flies. Yeasts love fruit flies because they help spread yeast cells like bees spread pollen.

So in order to send more flies their way, yeast developed the ability to give off smells that mimic fruit and flowers—favorite smells of both beer lovers and tiny insects. One particular gene called ATF1 helps the yeast make byproducts with fruit fly–attracting scents. Scientists discovered that mutant yeasts lacking ATF1 brought no flies a-calling.

What that means, according to the scientists, is that all those good beer smells have never been for us. We’re just interlopers on the hot and heavy relationship between yeast and fruit flies.

If being a third wheel makes you a bit uncomfortable, just have another beer. That always helped us get through an awkward evening.