Insomniacs take heart: Humans get by on significantly less sleep than our closest animal relatives. The secret, according to a new study, is that our sleep is more efficient. 
 
 Researchers from Duke University scoured the scientific literature and compiled a database of slumber patterns across hundreds of mammals including 21 species of primates -- from baboons and lemurs to orangutans, chimpanzees and people. They then used statistical techniques to account for each species' position in the primate family tree. 
 
 They found that humans are exceptionally short sleepers -- getting by on an average of seven hours of sleep a night, whereas other primate species, such as southern pig-tailed macaques and gray mouse lemurs, need as many as 14 to 17 hours. 
 
 What's more, our sleep tends to be more efficient, meaning we spend a smaller proportion of time in light stages of sleep, and more of our sleep time in deeper stages of sleep. A dream state called rapid eye movement sleep, or REM, for example, makes up nearly 25 percent of our overall sleep. But in primates such as mouse lemurs, mongoose lemurs and African green monkeys, REM sleep barely climbs above five percent. 
 
 "Humans are unique in having shorter, higher quality sleep," said anthropologist and study co-author David Samson of Duke, who logged nearly 2,000 hours watching orangutans in REM and non-REM sleep as part of his dissertation research prior to coming to Duke. 
 
 The human sleep gap isn't merely the result of round-the-clock access to artificial light from streetlamps and computer screens, the researchers say. A separate study of the sleep habits of people living in three hunter-gatherer societies without electricity in Tanzania, Namibia and Bolivia found they get slightly less shut-eye than those of us with electronic gadgets. 
 
 If artificial light and other aspects of modern life were solely responsible for shortening our sleep, we'd expect hunter-gatherer societies without access to electricity to sleep more, Samson said. 
 
 Rather, the study by Samson and Duke anthropologist Charlie Nunn suggests that humans replaced sleep quantity with sleep quality long before the glare of smartphones came to be. 
 
 The researchers attribute the shift towards shorter, more efficient sleep in part to the transition from sleeping in "beds" in the trees, as our early human ancestors probably did, to sleeping on the ground as we do today. 
 
 Once on the ground, Samson said, early humans likely started sleeping near fire and in larger groups in order to keep warm and ward off predators such as leopards and hyenas -- habits which could have enabled our ancestors to get the most out of their sleep in the shortest time possible. 
 
 Shorter sleep also freed up time that could be devoted to other things, like learning new skills and forging social bonds, while deeper sleep helped to cement those skills, sharpen memory and boost brainpower, Samson said. 
 
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 The findings appear in the journal Evolutionary Anthropology. 
 
 This research was supported by grants from the National Science Foundation (BCS-1355902) and Duke University. 
 
 A digital version of this story is available at http://today. duke. edu/ 2015/ 12/ humansleep . 
 
 CITATION: "Sleep intensity and the evolution of human cognition," Samson, D. and C. Nunn. Evolutionary Anthropology, December 2015. DOI: 10.1002/evan.21464 ||||| Have you ever woken up after 8 hours of sleep and thought to yourself that you could sleep for a few more? Perhaps something from your evolutionary past is calling to you. A new study suggests human sleep is more efficient than that of other mammals because we have evolved to sleep for fewer hours, in deeper sleep stages. 
 
 
 
 Humans have evolved to sleep for shorter periods in deeper sleep, say researchers. Humans have evolved to sleep for shorter periods in deeper sleep, say researchers. 
 
 The study, published in the journal Evolutionary Anthropology, examines sleep patterns across hundreds of mammals, including 21 species of primates such as baboons, lemurs, chimpanzees and humans. 
 
 According to the Centers for Disease Control and Prevention (CDC), how much sleep we need as individuals varies, but it changes as we age. For example, school-age children need about 10 hours of sleep each day, while teenagers need 9-10. 
 
 Adults need around 7-8 hours of sleep a day, but according to data from the National Health Interview Survey, almost 30% of adults sleep a reported average of less than 6 hours of sleep each night. 
 
 The researchers, led by anthropologist David Samson of Duke University in North Carolina, compiled a database of sleep patterns across mammals and then used statistical techniques to account for each species' hierarchy in the primate family tree. 
 
 Humans spend 25% of sleep in REM phase 
 
 The team found that humans are the shortest sleepers - slumbering for an average of 7 hours each night - while other species of primate, such as the southern pig-tailed macaques and gray mouse lemurs, need 14-17 hours. 
 
 Fast facts about sleep Sleep insufficiency is linked to car crashes, industrial disasters and medical or other occupational errors 
 
 In the US, 50-70 million adults have sleep or wakefulness disorder 
 
 On average, adults need 7-8 hours of sleep each night. Learn more about sleep 
 
 Additionally, the team found that our sleep is more efficient. We spend nearly 25% of our overall sleep in rapid eye movement (REM) sleep - which is a deeper stage of sleep - whereas other primates spend only 5% of their time in this sleep state. 
 
 Samson spent nearly 2,000 hours watching orangutans in REM and non-REM sleep as part of his dissertation research before he came to Duke. He notes that humans "are unique in having shorter, higher quality sleep." 
 
 In our modern world of artificial lights and gadgets with screens, it would be easy to blame technology for our shift in sleeping patterns, but the team says this is not the culprit. 
 
 A completely different study into sleeping habits of hunter-gatherer societies without electricity in Tanzania, Namibia and Bolivia concluded that they actually get less sleep than those of us in a tech-obsessed society. 
 
 Samson notes that if modern life were to blame for our shortened sleep, these hunter-gatherer societies that do not have access to electricity would presumably sleep more. 
 
 The 'sleep intensity hypothesis' 
 
 As a result of their findings, the researchers propose a "sleep intensity hypothesis," which suggests that early humans encountered "selective pressure" to get quality sleep in the shortest amount of time possible. 
 
 They write: 
 
 "Several factors likely served as selective pressures for more efficient sleep, including increased predation risk in terrestrial environments, threats from intergroup conflict and benefits arising from increased social interaction." 
 
 The researchers add that less sleep would give early humans longer periods of activeness, during which they could acquire new skills and knowledge. Meanwhile, deeper sleep is necessary to consolidate these skills and leads to "enhanced cognitive abilities." 
 
 Samson says the shift toward shorter, more efficient sleep likely coincided with early humans transitioning from sleeping in trees to sleeping on the ground, where they likely slept near fire and in larger groups to keep warm and ward off predators. 
 
 Medical News Today recently reported on a study that suggested the brain's ability to regulate emotions is compromised by fatigue, and sleep deprivation, therefore, affects our ability to allocate brain resources for cognitive processing.
– Ever wonder why your cat sleeps all day while you're stuck with the measly seven hours you can cram in between Scandal and your morning commute? As it turns out, you're just way better at sleeping than your furry friend. According to a study in Evolutionary Anthropology, humans evolved to be the most efficient sleepers in the primate family. Researchers from Duke University studied the sleep patterns of 21 primate species and hundreds of other mammals, according to a press release. They found humans sleep less than most primates—the sleepiest of which gets as much as 17 hours per night. But humans also sleep deeper than other animals, with 25% of our shuteye coming as REM sleep; some primates get as little as 5%. Researchers hypothesize that when our ancestors came down from the trees, a change in sleep patterns proved beneficial, Medical News Today reports. Less time spent sleeping on the ground meant less time to be eaten by a lion or attacked by a rival tribe and more time for social interactions and other benefits. "Less sleep would enable longer active periods in which to acquire and transmit new skills and knowledge, while deeper sleep may be critical for the consolidation of those skills, leading to enhanced cognitive abilities in early humans," the study states. So—as Gizmodo puts it—the fact that we're "burning the candle at both ends" might explain "why humans are playing with iPads while the rest of our close family is still throwing poop." (In fact, another study shows ancient humans may have slept even less than we do now.)