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Don: Some people seem to need significantly less sleep than others.

Yael: Tell me about it. I have a friend who swears that she sleeps only five hours a night. If she's telling the truth, then she must be bionic. She seems to have plenty of energy, and she's not fuzzy-brained and incompetent¹ the way I am after several nights of only five hours of sleep. You know what really irks me? Because she sleeps less, she has more time to accomplish more in her days than I do. It's not fair.

D: I know what you mean. I need eight to nine hours of sleep a night myself. What I would do for three more hours every day! That's twenty-one more hours a week!      I'm getting off track though. Scientists have discovered a gene² in fruit flies that determines how much rest the individual needs. Fruit flies with a version of this gene are actually programmed to need less sleep than others. And humans possess a similar gene.

Y : So the amount of sleep one needs seems to be genetically³ inherited?

D: Yes. And families of flies with a lower sleep requirement don't seem to suffer any      impairments in their performance of daily tasks. It may very well be that people who      claim to need less sleep to operate normally are telling the truth.

Y: That's depressing.

D: Well, you might be interested to know that flies programmed to sleep less tend to die earlier.

Y: Really? So maybe I'll end up with the same hours of waking time as my friend after all. It'll just take me a few extra years of living to catch up with her!

D: Maybe.