Evolving Sleep Patterns
![](https://media.wnyc.org/i/800/0/l/85/1/19955286013_f57b49426c_o.jpg)
People Sleeping on Subway
( Richard Yeh / WNYC / flickr/CC-BY-2.0 )
( Richard Yeh / WNYC / flickr/CC-BY-2.0 )
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