Why do we need to sleep? Part of what makes sleep so fascinating, as a field of research, is that it is such an enigma. Sleep is a profoundly vulnerable state, leaving us at the mercy of predators and the environment, and unable to defend ourselves or our possessions. It's also largely unproductive. Yet we spend about a third of our life in slumber. Moreover, sleep also seems to be nearly universal in the animal kingdom. Indeed, we have yet to identify an animal that clearly does not sleep at all, or even one that can forego sleep without experiencing physiological consequences. All of this, taken together, unambiguously shows that sleep is extremely important. And this makes it all the more remarkable that the actual purpose of sleep remains elusive. One idea is that sleep may function as an antioxidant for the brain, protecting neural tissue from the ravages of oxidative stress. This hypothesis largely fell out of favor, but researchers have recently started to revisit this compelling notion. In this episode of humanOS Radio, Dan talks to Mimi Shirasu-Hiza. Mimi is an associate professor of Genetics and Development at Columbia University. Her lab uses circadian mutants of fruit flies to unveil the molecular mechanisms that underlie circadian-regulated physiology. Mimi and her colleagues hypothesized that fruit flies with various genetic mutations that reduce their sleep might share a common physiological defect due to that sleep loss, but independent of the specific mechanisms driving their reduced sleep. And if they could find such a defect, that might reveal the core function of sleep in animals (including us). Through an elegant series of experiments, Mimi and her team did indeed uncover a shared defect, which points to a possible purpose of sleep in fruit flies and perhaps in humans. Check out the interview to find out what they discovered and what it might mean for us!