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In search of the origin of sleep; Which creature took a nap for the first time?

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Shirley JacksonIn 1959, the American writer wrote in the first line of his horror novel “Hunting the Hill House”: “No living being can survive for a long time in absolute reality with mental health. Even cuckoos and crickets dream.”

Jackson He wrote the above line to introduce the haunted house of his story; Where the border between reality and dream was always blurred, but he was right; Most living things need to be away from reality at least for a while in order to remain active and alive.

Quoted from Scientific American websiteThroughout the animal kingdom, “sleep” appears to be very different from what humans do. Humans enter a dreamlike state of unconsciousness when they sleep, dolphins turn off parts of their brains piecemeal, and giant puffin birds take brief naps of a few seconds while soaring through the air.

However, almost all animals sleep. Over the past decade or so, researchers have discovered that even brainless creatures such as jellyfish and hydras (freshwater creatures with the simplest body plan of all living things) do something very similar to napping. Now, the question arises, what was the first creature that experienced sleep?

Of course, there are no preserved resting places with fossils of tiny ancient creatures snoring in succession. Although no one knows for sure, the first napping probably occurred more than half a billion years ago, and was certainly done by a very simple creature.

Michael Abramsa postdoctoral researcher from the University of California, Berkeley, was one of the members of the research team that in 2017 Discovered A type of mermaid called Cassiopeia experiences a sleep-like state on a regular basis. “It seems to me that when animals have a nervous system connected to muscles, they almost certainly experience sleep,” he says.

Scientists have not yet determined the exact date of this event, but the presence of nervous system in living organisms goes back to the very distant past. According to A study in 2019, the first organisms to grow neurons were small, flat, plate-like organisms called Dickinsonia that fed on microbes during the Ediacaran geological period, between 635 and 542 million years ago. Although it is not known for certain whether these creatures were actually the first species with a nervous system, neurons probably evolved around this time, before the massive expansion of species on Earth during the later Cambrian period.

But there is still disagreement about whether living organisms without a nervous system, such as sponges or even plants, sleep. Taichi Aita A chronobiology researcher from Kyushu University in Japan says: “The nervous system may not be necessary to prove the experience of sleep; Nobody knows. “We are still looking for the origin of sleep.”

Every time you sink into your bed and take a trip to dreamland, you’re actually engaging in a biological imperative that promotes cell growth, consolidates memories, reduces inflammation, and, when done right, keeps you alive. . But sleep is very strange. Why should organisms shut the door to the outside environment for hours and hours, leaving themselves vulnerable to predators and other environmental hazards?

This question is the curiosity of researchers like Ayatah And Abrams has also provoked Abrams says:

Sleep was once thought to be the domain of creatures with brains, but as mentioned earlier, Abrams And his colleagues discovered that the mermaid Cassiopeia also apparently sleeps. This species spends most of its time in the shape of a bell on the ocean floor and beats regularly. Based on this behavior, the researchers were able to determine the activity level of the jellyfish.

In the laboratory, the researchers tracked the pulse rate of the jellyfish over time and found that the pulse activity of the jellyfish at night was 32% lower than during the day. The jellyfish had a delayed reaction to the bottom of the tank being dropped from under them, but would slowly “wake up” if they were fed. When Cassiopeia lost her peace during the night due to the disturbing movements of the water, the next day she had a slower and longer pulse and was less responsive to stimuli; Just like he is sleep deprived.

In a similar experiment, Ayatah and his team in an article published in 2020 in the journal Science Indonesia published, reported that small hydras of vulgaris species also have a dormancy period that is very similar to sleep. In the study, hydras were completely still during the test periods and could be awakened by a light pulse, but after about 20 minutes of silence, they barely responded to such pulses and entered a state that was very similar to dozing. When the hydra were deprived of this sleep-like period by stimulating vibrations applied to their tank, they slept longer and fell asleep more quickly the next time.

For the researchers, these quiescent periods in jellyfish and hydras represent all aspects of sleep: a reduction in activity that is reversible in response to disturbance; Delayed response to stimuli, slowing of performance after rest period deprivation, and increased motivation to sleep more when rest time is lost.

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