听新闻回答问题并填空 1. What percentage does REM make up a human’s sleep? REM makes up _______________ of a human’s sleep. 2. How many hours of sleep do humans need on average a day? Samson’s research team found that humans can prosper with an average of______________ of sleep a day. 3. How did human sleep habits evolve? Human ancestors moved from ____________ to ______________.