I am not too surprised... all countries are relatively close to the equator (Score: 2, Interesting) by email@example.com on 2015-10-20 19:16 (#R399) The closer you are to the equator, the less is the difference between day time and night time over the year. In spring and summer, where the days are long, I also need very little sleep. 5-6 hours. Absolutely within the range of above mentioned societies. In autumn and winter sometimes even 9hrs are not enough for me. Fortunately I can 'extend' the days with certain light sources.And that is exactly what the article says:Hunter-gatherers sleep an hour more in the winter than they do in the summer.Even though:It appears that their sleep time may have more to do with temperature than with light.Maybe. The temperature in my bedroom is almost constant over the year... so no own experience here.But I really would like to know, if there is a correlation of distance from the equator and sleep time.Namibia is farthest away from the equator. Could it be that there the sleeping time is more in the 7.1 hour range? While in Tanzania, which is closest to the equator, the time is more in the 5.7 hour range? Re: I am not too surprised... all countries are relatively close to the equator (Score: 1) by firstname.lastname@example.org on 2015-10-20 21:35 (#R3NJ) My room varies tremendously in temperature (40Â°-115Â°F between late night winters and midday summers â€” itâ€™s in a steel warehouse) and it is impossible to sleep late when itâ€™s hot. Conversely, itâ€™s hard to get out from under the covers when itâ€™s cold. A preindustrial society wouldnâ€™t be able to do much about the temperature but they would have a way of insulating themselves from light so as not to be woken by the sunrise shining on their faces. I suspect thatâ€™s why the authors went with temperature as the main factor. Re: I am not too surprised... all countries are relatively close to the equator (Score: 1) by email@example.com on 2015-10-20 22:15 (#R3R8) Pre industrial societies have access to fire, too. It would be very easy for them to maintain warmer temperatures. Re: I am not too surprised... all countries are relatively close to the equator (Score: 1) by firstname.lastname@example.org on 2015-10-21 18:01 (#R6RD) People living in the tropics would be more interested in making things cooler than warmer, I reckon.