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Why did sleep evolve?

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Sleeping may seem like a waste of time (unless you're having a well-deserved lie in), but it's critical to a healthy waking life.

Asked by: David Abell, Portsmouth


Scientists disagree as to why sleep evolved. It seems peculiar that we should spend so much of our lives sleeping when it’s at this time that our vigilance is at its lowest and we’re at our most vulnerable. It’s also a time when we don’t typically eat, drink, or reproduce.

There are a plethora of theories as to why sleep evolved, including the idea that sleep allows us to save or optimise our energy use and keep us alert to danger. Sleep also allows us to clean toxins from our brains and consolidate memories, and it’s increasingly clear that it helps in many aspects of our waking lives, from controlling our weight and regulating our emotions, to bolstering our immune systems.

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Alice is a Professor of Psychology at Goldsmiths. She has contributed to several diverse research areas, including the longitudinal associations between sleep and psychopathology, behavioural genetics, sleep paralysis and exploding head syndrome. In addition to her scientific contributions she also excels in the public engagement of science. She has published two popular science book (Nodding Off, Bloomsbury, 2018 and Sleepy Pebble, Nobrow, 2019). She regularly contributes articles to the media and has had her work published in outlets including the Guardian, GQ UK, Sud Ouest, Slate Fr, Independent.


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