It's not a question you might have thought about, but which came first: sleep or the brain? To put it another way, can organisms without brains go to sleep? Based on a study of primitive, water-dwelling life forms called
Hydra vulgaris, scientists might finally have the answer.
New research shows how these tiny creatures can enter a sleep-like state despite not having brains – and that could teach us a lot about how animals evolved the need and capacity for sleep.
What's more, the team behind the study found that the chemicals that bring on drowsiness in human beings had the same sort of effects on
Hydra vulgaris, suggesting a biological link across the species, despite our vast differences.
"We now have strong evidence that animals must have acquired the need to sleep before acquiring a brain,"
says biologist Taichi Itoh, from Kyushu University in Japan. "Based on our findings and previous reports regarding jellyfish, we can say that sleep evolution is independent of brain evolution."
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