Humans need less sleep than other mammals, yet their slumber is more efficient, said researchers at Duke University in North Carolina.

In their study, the scientists researched sleep patterns of hundreds of animals. They discovered humans sleep for shorter periods of time compared to other animals.

The study also concluded that a human's sleep is higher quality. A deeper stage of sleep, called rapid eye movement sleep, or REM, makes up 25 percent of a human's sleep. In primates like lemurs or monkeys, REM sleep does not reach the five percent mark.

"Humans are unique in having shorter, higher quality sleep," said David Samson, a study co-author.

Samson's research team found that humans can prosper with an average of seven hours of sleep a day. Other primates need as many as 14 to 17 hours of sleep.

Samson said human sleep habits evolved during prehistoric times. Human ancestors moved from sleeping in trees to sleeping on the ground. Better sleeping habits resulted in better sleep in a shorter amount of time.

I'm Mario Ritter.

Jim Dresbach adapted this story from VOA News for Learning English. Kathleen Struck was the editor.