But what if such sleep cycles existed in a common ancestor?
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Researchers in a German laboratory have revealed some interesting details about the sleep patterns of reptiles.
Lizards share sleep patterns with humans, according to scientists.
As per the researchers, main thing is how different group of animals are linked to each other.
Amniotes appeared around 320 million years ago and quickly branched off into a group that led to the mammals, including humans and another that led to the reptiles and the birds. Dr. Gilles Laurent, of the Max Planck Institute for Brain Research in Frankfurt and co-author of the study, stated while addressing Huffington Post.
The reptiles showed a style of sleep that was very much like the mammals and birds. This discovery could establish an important discussion about the evolution of sleep.
Yet, birds are reptiles-they are the feathered descendants of the now extinct dinosaurs.
Also, while in reptiles SW and REM sleep have roughly equal durations during each cycle, REM is much shorter then SW sleep in mammals, and both short and irregular in birds.
If reptiles go through REM sleep, does that mean they’re also dreaming?
“[The study provided] extremely strong evidence that the patterns of structure of sleep that we’ve seen in a broad range of species is reflective of something that evolved very early in vertebrate evolution and is shared across many – perhaps all – vertebrates”, Dr. Daniel Margoliash, a professor of organismal biology and anatomy at the University of Chicago who was not involved in the study, told The New York Times.
He added: “It forces us to think about the earliest evolution of these phenomenon”.
“It poses many questions: How did sleep start?”
Scientists watched them while they slept and concluded that they may have REM sleep like us – which could prompt a fundamental reassessment of how sleep evolved.
Mammals and reptiles diverged from that common ancestor in two distinct lineages. During REM sleep the eyes move rapidly, the blood pressure and heart rate rise and the limbs are paralyzed.
A team of researchers in Germany announced in a report published on Thursday (April 28), however, they had found evidence of similar sleep stages in a lizard: Specifically, the bearded dragon, or Pogona vitticeps, a reptile native to Australia and popular with pet owners. The duration of human sleep cycle was put at between 60 and 9 minutes while the sleep cycle for cats 30 minutes and just about 80 seconds in the case of lizards. Unexpectedly, the researchers found that these brain patterns originated from the anterior dorsal ventricular ridge and not from the cortex. To conduct the study, researchers recorded the brain activity of lizards when they were sleeping.
Scientists have long believed that only birds, humans, and other mammals went through rapid eye movement (REM) and slow-wave sleep (SWS).
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“We had a characterization that was starting to become more and more like what we observe in mammalian sleep”, Laurent said.
