Sleep serves multiple functions, some of which are still not understood. To determine what goes on during sleep, and why it is so crucial for every species from the fruit fly to the jellyfish, a trio of Penn experts published a piece in Nature Reviews Neuroscience looking at sleep function across phylogeny—that is, the evolutionary development of species—to find the origins of the need for sleep.
We know that sleep plays a critical role in the evolution of many species—just think about how often an infant needs to sleep to grow and develop—but what is still not clear is whether the original purpose for sleep remains the same today.
Drawing from previous work in fruit flies—which, like humans, have a central nervous system and a brain, and sleep and wake periods that follow a 24-hour circadian rhythm—the authors speculate that the functions of normal, healthy sleep, and those of recovery sleep (following sleep deprivation) are very different.
“The field needed well-designed research into healthy sleep across the evolution of various species to find what the original point of sleep really is,” said David Raizen, an associate professor of neurology and senior author on the research. “The debate about the function of sleep continues—but is now informed by remarkable findings in the expanding world of sleep and chronobiology research in multiple species.”
Read more at Penn Medicine News.