才几点你就睡？起来嗨！

我们常常责怪电子灯光、电视、互联网以及咖啡因让我们的睡眠时间匮乏，特别是与没有这些奢侈品出现时相比。而且我们也常说睡眠缺乏是体重超标、情绪问题以及其他现代病的原因。这种说法有一个毛病，其实并没有人真的知道在咖啡或者霓虹灯出现之前人们到底睡多长时间。
来自于加州大学洛杉矶分校的Jerome Siegel博士和Yetis做了一个研究，试图给出个答案，研究结果公布在current biology。他们观察了三组以工业化前生活方式（确切的说是农业化前）生活的人群，并测量他们的睡眠曲线是否有别于现代的都市人，他们的研究结论令人吃惊，因为他们发现实际上区别并不大。
研究中的三组人群分别是坦桑尼亚北部的Hadza人，非洲南部生活在Kalahari沙漠的Ju/’hoansi San人，以及玻利维亚的Tsimané人。他们都是靠狩猎和采集为生的部落人。Siegel博士与Yetish找到了94位志愿者，让他们佩戴仪器来监测他们的动作水平，监测皮肤表面的血管收缩的时间（这用来监测不在恒温环境下的人醒来的过程，因为醒来时血液会流向大脑和其他内脏，引起靠近皮肤表面的血管收缩）。他们还在志愿者休息的地方放置了温湿度监测设备，用来甄别志愿者是否醒来或者进入睡眠状态。
最终，研究者收集到了1165天的有效数字，他们发现，这三组志愿者的睡眠时间都在5.7到7.1小时之间，平均值为6.5小时。与之前的猜测恰恰相反，他们的睡眠不但没有比现代人长，而且仅达到了工业社会睡眠数据的低限，而城市居民的睡眠时间的平均值为7.5个小时。
研究发现这三组来自不同地区的志愿者并不是日落而息，相反，他们在日落后平均还有3.3个小时的时间是清醒的，就像发达社会一样。他们的上床睡觉时间往往是根据气温来定而不是日光，而往往日落后还有几个小时环境才会变冷。
这个研究也对午睡提出了质疑，之前我们常说现代生活方式剥夺了人类的午睡的权利。而研究发现，这些部落生活方式的志愿者夏天几乎从不午睡，而冬天从来没有午睡过。
然而研究还是发现了一些差异，比如从事狩猎采集的部落人在季节之间的睡眠差异比较大，他们在冬天普遍比在夏天多睡一个小时，然而现代人的冬夏睡眠时长差异只有二十分钟。更令人感兴趣的是，部落人几乎从来不会出现失眠状态，而现代社会有将近超过20%的人都有失眠的困扰。
部落人的生活有什么值得现代人学习的？呵呵，尚未知。嗯，也许对他们的生活进行更近距离的研究能够找到减少失眠的方法。
不过，如果下次有人说人类需要午睡是自然规律，半夜可不能参加派对什么的，别信他，只管去，么么哒。
［火金］唉，花了两年多跑那么远，浪费了这么多智能穿戴设备，得出了这么个无聊的结论……呔！研究经费瞎胡花！浪费！（粉色好好看）

－－－－－－原文，破折号————————
Now I lay me down to sleep

Modern life has not changed sleeping patterns as much as some believe

ELECTRIC lighting, television, the internet and caffeine all get blamed for reducing the amount of time people sleep compared with the days before such luxuries existed. Such alleged sleep deprivation is sometimes held responsible for a rise of obesity, mood disorders and other modern ailments. The trouble with this argument, though, is that no one really knows how long people slept before coffee and light bulbs existed.
A study just published in Current Biology by Jerome Siegel of the University of California, Los Angeles and Gandhi Yetish of the University of New Mexico tries to provide an answer. Dr Siegel and Mr Yetish looked at three groups who cleave to pre-industrial (indeed, pre-agricultural) ways of life, to see if their sleep patterns differ from those of wired, urban humanity. To some surprise, they have found that in many ways they do not.
The groups in question are the Hadza of northern Tanzania, the Ju/’hoansi San of the Kalahari Desert, in southern Africa, and the Tsimané in Bolivia. All live largely by hunting and gathering. Dr Siegel and Mr Yetish asked for volunteers, and 94 people agreed to collaborate with them by wearing devices that recorded their level of movement, and also when the blood vessels near their skin were constricting. (This happens when people who do not live in environments managed by thermostats wake up: it makes more blood available to the brain and other internal organs.) Dr Siegel and Mr Yetish also put humidity- and temperature-monitoring devices in the areas where their volunteers tended to rest at night, in order to find out if these variables helped determine when they went to sleep and woke up.
In total, the researchers collected 1,165 days’ worth of data. They found that people from all three groups slept for between 5.7 and 7.1 hours a day, with an average that hovered around 6.5 hours. Far from exceeding those of a modern city-dweller, these values are near the low end of the range found in industrial societies. An average 7.5 hours a night is the norm there.
Nor did the Hadza, the Ju/’hoansi San or the Tsimané retire shortly after the sun went down. Rather, they stayed awake for an average of 3.3 hours after nightfall, much as people in the developed world do. Their bedtimes appeared to be regulated by the temperature, rather than by daylight, and it takes several hours after the sun has set for things to cool down.
The study also calls into question the idea that siestas are a feature of human behaviour that has been suppressed by modern ways of life. The volunteers rarely napped in summer (doing so on about one day in five), and almost never in winter.
There were some differences. One was that hunter-gatherers exhibited a bigger seasonal variation in the amount of sleep they took than “modern” folk do. They slept almost an hour longer in winter than in summer, whereas the wired sleep about 20 minutes longer. Perhaps more intriguingly, they barely suffered from insomnia, a complaint prevalent in more than 20% of the population of industrial societies.
Whether those who hunt and gather have anything to teach the modern world, then, is moot. A closer examination of their lives may reveal ways of reducing insomnia. But the next time someone claims a siesta is a natural part of human life, rather than a response to partying after midnight, be sceptical.

原文刊于《The Economist》