Humans have evolved to become more efficient with their sleep, and need less than half the amount of resting time than some of our closest relatives, a new study has revealed.
The average human sleeps for an average of seven hours a night, but some monkeys such as southern pig-tailed macaques and gray mouse lemurs need up to 17 hours a day to get by.
Research carried out at the Duke University analysed a heap of scientific literature to create a database which contained information on the sleeping patterns of hundreds of mammals, including 21 species of primates. They then correlated the information with each species' position on the primate family tree.
Although humans are short sleepers, we have grown to be more efficient with our sleep, and spend a shorter amount of time in the light sleep stages. For example, humans spend 25% of their average sleep in a rapid eye movement (REM) state, whereas mouse lemurs, mongoose lemurs and African green monkeys spend just 5% in an REM state.
"Humans are unique in having shorter, higher-quality sleep," said anthropologist and study co-author David Samson in the paper published in Evolutionary Anthropology. However, researchers are quick to point out that we haven't adapted to shorter amounts of sleep due to artificial lights such as street lamps, as the study proved that electricity-free societies in Tanzania, Namibia and Bolivia get less sleep than those in a typical Western World society.
What they do partly attribute it to however is sleeping on the ground, as opposed to sleeping in trees. Once we had moved down from the branches, we were able to group together to keep predators at bay and keep warm, providing an altogether more comfortable experience.