Jellyfish and sea anemones are curious creatures: these organisms evolved without a brain and, as scientists discovered only in the past few years, don’t need one to sleep. The animals do, however, have neurons—nerve cells that appear interconnected throughout their body. And now a new study shows that how these animals sleep is surprisingly similar to humans, suggesting that sleep may have evolved before even the most primitive brains.
“This confirms that sleep allows a window for key housekeeping tasks,” says Philippe Mourrain, an associate professor of psychiatry and behavioral sciences at Stanford University, who studies sleep. Mourrain was not involved in the new study.
The new work shows this function of sleep has been conserved across evolution, he says, from the animals, such as primates, that have one of the most complex brains to cnidarians, such as jellyfish, which have none.
Missed this one. Important.
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