The cycle persisted for nearly the entire lifespans of the fruit flies (typically 40 to 50 days in the lab), robbing them of over 95 percent of the sleep they might have otherwise gotten. But when the researchers tracked survival in the sleep-deprived flies, they discovered that the hardship they’d endured had little effect on longevity. There were almost no detectable differences in lifespan between the perturbed flies and their well-rested counterparts, regardless of the duration of their dozing.

These results are “striking,” Akhund-Zade says. But they’re a far cry from proving that sleep is a worthless pursuit—especially outside the context of fruit flies in a lab.

“Our point is not, ‘Sleep is useless,’” Geissmann says. “Our point is that it’s not vital in these conditions, and it’s already quite different than what we assumed.”

The findings also can’t be generalized to animals—especially humans—without further research. “It’s a big leap to go from looking at flies in a controlled experiment to a [human] life,” Gasperetti says.

Even from the fly’s perspective, there are still a couple caveats to keep in mind. While the researchers’ meddling clearly severely disrupted the insects’ natural sleep patterns, other scientists are a little more hesitant to definitively say the flies never napped at all.

Twenty seconds of immobility isn’t long, but it’s still, well, 20 seconds. Quick dips into slumber are something even human bodies do naturally, Gasperetti says—a familiar experience for anyone who’s ever nodded off in a classroom or behind the wheel of a car. When added up, these short periods may have been just enough to keep the flies alive.

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And for flies, there may be ways to rest up without halting movement altogether, Vecsey says. The tubes holding the captive flies only rattled them awake after they’d gone completely still, but it’s possible that flies may be snoozing on the go.

It sounds odd, but there’s precedent: Dolphins are able to sleep one brain hemisphere at a time, which keeps them from drowning during periods of rest underwater. Even humans aren’t frozen in place during slumber. “Our definitions for sleep may need to be more flexible, especially across different species,” Vecsey says.

Even so, the body can only rejuvenate so much during brief respites of low-quality slumber. These flies were clearly being stripped of opportunities to hit the hay—and the absence of serious consequences on longevity remains compelling, Akhund-Zade says.

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When dolphins sleep, they shut down only one hemisphere of the brain at a time. The other half of the brain stays awake to keep the dolphin breathing, moving, and aware of its environment. Image Credit: Riccardo Cuppini, flickr

Notably, there’s no guarantee that the lack of sleep had zero effect on the flies. While there were pretty negligible effects on the insects’ longevity, the study didn’t test the flies’ cognitive abilities. Across species, learning and memory are both known to take a serious hit from sleep deprivation—and while life in a lab is cushy, a decline in mental acuity would probably have a severe impact on survival in the wild, Akhund-Zade says.

In this vein, Beckwith thinks there might be stratification in animals’ “need” for sleep. “Sleep is not a binary thing, like ‘we are okay’ or we die,” he says. “Maybe there are three parts to it. Maybe we need a certain amount to survive, then some to be functional, then the rest is accessory.”

That theory awaits confirmation. But in the meantime, those vexed by the idea of sleepless insects in their kitchens can rest assured: Their time is better spent catching z’s instead of flies.

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