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If you’re a night owl, you probably know that no matter how much coffee you chug in the morning you'll never function as well as you do after the sun sets. And early birds feel the same way about the evening. But instead of feeling guilty for your lack of round-the-clock awesomeness, blame your genes, says a group of researchers at the University of Leicester.

For the first time ever, scientists have identified genes responsible for one's "chronotype," or preference for morningness or eveningness, according to preliminary research published in the journal Frontiers in Neurology. Well, technically, they discovered these genes in fruit flies—more on that below.

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While scientists knew there was a genetic component to being more active during the morning or evening, they had been unable to identify the individual genes and specific molecular events behind our individual circadian rhythms (a.k.a. body clocks). Until now.

Larks and owls

So how did the researchers do it? Fruit flies! Turns out fruit flies share a surprising number of genes with humans and other mammals, and they also have their own tiny version of a body clock. Some of the genes that affect fruit flies' chronotype are just as critical in humans, the researchers say.

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You see, with fruit flies, their biological clock dictates the exact moment they emerge from their pupal case, so it’s easy to identify their chronotype. While most flies undergo this process (known as "eclosion") in the morning, some strains emerge at night.

Eran Tauber, a professor in Leicester’s genetics department and one of the study’s authors, told Fusion that he and his team studied fruit flies' behavior and identified two different strains: "Lark flies" and "owl flies." (Basically, a cute description for "morning flies" and "night flies.")

Tauber and his team extracted and sequenced RNA from the two strains, then analyzed and compared the sequences with a software that identifies molecular pathways—the series of molecular events that regulate gene expression.

Multitalented genes

After looking at the 16,000 genes in the fly genome, Tauber and his team identified 80 genes that showed very big differences between "larks" and "owls," the researcher told Fusion. “We expected to find many genes that directly relate to the circadian clock, but many of the genes … were non-clock genes.”

In other words, "larks" and "owls" showed genetic differences that extended beyond the genes that regulated their body clocks. For example, researchers saw differences in the tailles gene (which affects the development of photoreceptors in the eye) and the huckebin gene (which influences the development of the innermost layer of cells in an embryo).

The researchers also discovered that "lark" and "owl" genes expressed themselves differently. “For the owls, if you look at the gene expression, it’s not a simple case where everything is delayed,” Tauber said. “There is activation of different pathways in the owls compared to the larks.”

So let’s say gene expression is like catching the subway: Early-bird larks will catch the A train into Manhattan bright and early, but night owls might take a different route entirely. Even though they end up at the same destination, the biochemical events that make one organism a "lark" and another an "owl" are different. “Once a cascade of molecular processes starts,” Tauber explained, "if it’s slightly late, it goes into a different route or different direction.”

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Of course, Tauber and his team need to conduct much more research to determine if the same is true for mammals and humans. But given these findings, scientists may start to look at our body clocks less as an internal pacemaker and more as a complex interactive system that internalizes various environmental cues (like light).

As for the practical implications, while most of us aren’t extreme larks or extreme owls, some folks really are deeply governed by body clocks, and messing with their sleep schedule can have a serious effect on performance and health. The researchers hope that understanding the genetics of what drives a person’s chronotype will one day help to create better and more accurate diagnoses for ailments related to the circadian rhythm.