A groundbreaking study published in *Nature Communications* has provided compelling evidence that jellyfish, ancient marine invertebrates without centralized brains, exhibit sleep-like states remarkably similar to those observed in humans. This research, building upon earlier findings from 2017 on *Cassiopea* jellyfish, expands to include sea anemones, reinforcing the idea that sleep is a fundamental biological necessity predating the evolution of complex brains. The scientists observed that jellyfish display key characteristics of sleep: periods of reduced activity (quiescence), decreased responsiveness to external stimuli, and a homeostatic need for sleep, meaning they show increased "sleep pressure" following deprivation. For instance, the upside-down jellyfish (*Cassiopea andromeda*) pulses its bell less frequently at night and is slower to react when disturbed. Intriguingly, both jellyfish and sea anemones were found to sleep for approximately eight hours a day, a duration comparable to human sleep, with jellyfish primarily resting at night and even taking midday naps. A pivotal aspect of the latest findings is the discovery that sleep in these brainless creatures plays a crucial role in repairing DNA damage within their neurons, a function conserved across the animal kingdom. Wakefulness was associated with increased neuronal DNA damage, which decreased during sleep. Furthermore, intentional DNA damage led to increased sleep, highlighting its restorative importance. This suggests that one of sleep's most ancient and vital purposes is to safeguard nerve cells from cellular stress, offering profound insights into why sleep is essential for human health and for the very survival of diverse life forms.