We all sleep. And by “we all” I mean all animals from bugs to bird to people. And sleep looks the same on us, from the outside. We lie down, close our eyes, stay still But on the inside – what our brains are doing during sleep – was thought to be unique to birds and mammals. During sleep for these animals, the brain exhibits two different patterns of activity – slow-wave sleep and rapid-eye movement or REM sleep. But now, it looks like reptiles have a similar pattern of activity in their sleep: REM sleep alternating with a slow-wave type sleep throughout the resting period. Researchers were able to measure this type of sleep in lizards for the first time using implanted electrodes, infrared cameras and elaborate analysis. One unique aspect of lizard sleep – the lizard’s sleep cycle is only about 60-90 seconds long In humans, our complex sleep cycles last 60-90 minutes each! Does this mean that lizards have short, frequent dreams? It’s still too early to tell if lizards or even birds dream during their sleep But what we do know is that our sleep patterns are a lot older than once thought— at least 300 million years old. Because lizards may be more similar to our shared common ancestor, studying sleep in the reptile brain may be the best way to learn more about how sleep works for everyone.