The sleep patterns of reptiles might not be all that different from humans and other mammals. Previously, researchers believed that only mammals and birds go through the slow-wave sleep (SWS) and rapid eye movement (REM) when they snooze. However, scientists have found the same sleep patterns in the Australian bearded dragon, a non-avian reptile.
Dinosaurs may have had the same sleep patterns
Findings of the study were published in the journal Science. Researchers led by Dr Gilles Laurent of the Max Planck Institute for Brain Research in Germany found that the SWS and REM sleep rhythms may have emerged more than 300 million years ago in a common ancestor. Even dinosaurs may have followed the same sleep rhythms. To conduct the study, researchers recorded the brain activity of lizards when they were sleeping.
The reptiles show alternate cycles of deep sleep and eye movements, just like humans and other mammals. Typically, humans go through four or five cycles of SWS and REM, with each cycle lasting 60-90 minutes. However, scientists found that the lizards’ sleep patterns are faster and more regular. Their sleep cycles of SWS and REM last between 60-80 seconds. In bearded dragons, the activity originates from a different part of the brain than mammals.
Mammals and reptiles evolved from a common ancestor
The fact that humans, birds and reptiles share the same sleep rhythms indicates that they all evolved from a common ancestor 300 million to 320 million years ago. Back then, the land was dominated by amniotes, the four-legged animals that laid eggs with a protective amniotic membrane. Dr Gilles Laurent said the amniotes were lizard-like small animals.
Researchers said the reptiles even dream, albeit in a rudimentary way. Reptiles and mammals diverged from their common ancestor in two distinct lineages. Thanos Siapas, professor of neural systems at the California Institute of Technology, told BBC that the study sheds light on “how the architecture of sleep evolved.” Siapas was not involved in the study.