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Sleep researchers have long puzzled over why some people feel alert in the early morning while others come alive only at night. Recent studies suggest that these differences are shaped partly by genetics, which influence the timing of a person's internal body clock. Importantly, this means that a 'night owl' forced to wake at dawn is not simply lacking discipline; their biology may genuinely be out of step with the schedule society imposes. Some scientists argue that workplaces and schools could improve both wellbeing and productivity by allowing more flexible start times that better match individual rhythms.