ＴＥＤのホームページへは
をクリックしてください。
直接、ここ
で観ることもできます。
小さいことは気にすんなッ、主題と主張をつかもう！
僕はいつも夜中に目が覚めてしまうのが気になっていたのですが、それが自然なのだと知って安心しました。
【話題】 体内時計と睡眠サイクル
【時間】 ４分１秒
【要約】
１．体内時計
生命は光と闇の繰り返えしの中で進化してきた。
全ての多細胞生物と一部の単細胞生物も持っている。
（例） カニを海岸でつかまえて、大陸の反対側へ飛行機で運ぶと、もともと生殖していた海岸の潮の満ち引きに合わせてカゴの中を登ったり降りたりする。内部的な周期を持っているからだ。
２．人間も体内時計を持っている。
時計の無い、地下深くの穴ぐらにヒトを二、三ヶ月間 閉じ込めてると、不規則な睡眠パターンになかと思いきや、実際は決まったパターンで生活する。毎日15分くらいづつ遅く起きるが、外界を感知するのではなく、自身の体内時計に基づき行動する。
３．体内時計は文化に強く影響を与えている。
その影響力が著しく過小評価されている。
（例） 赤道近くの人間と北方先住民の文化の違い。
４．自然なリズムでの理想的な睡眠パターン
全く人工的な照明が無い 環境で生活すると人は毎夜２回眠る
「午後8時頃から午前零時まで」と「午前2時頃から 日の出まで」の２回
その中間は、２～３時間程の瞑想的な静寂の時間があり、プロラクチンの高まりが見られる。この実験に参加した人は、日中、眠気を感じなかった。
５．現代人の生活
現代人は時差ボケ、長距離旅行、24時間営業、シフト勤務の世界に生きている。もちろん利点もあるが、マイナス面も理解すべきだ。
【語彙】
internal clock, chemical clock, body clock ：体内時計のこと
plot ：筋書き、仕組み
correspond ：対応する
bunker ：貯蔵庫、倉庫
rave about ：絶賛する、よろこんで実験に協力してくれたということでしょう
atypical ：通常とは異なる
drift ：少しづつズレていくこと
driver ：突き動かすもの、推進力
underrate ：過小評価する、見くびる
evolve ：進化する
perpetual ：終わらない、永遠の
meditative ：瞑想的な
surge ：急に増加すること
prolactin ：プロラクチン、黄体刺激ホルモン
jet lag ：時差ボケ
【transcript】
Let's start with day and night. Life evolved under conditions of light and darkness, light and then darkness. And so plants and animals developed their own internal clocks so that they would be ready for these changes in light. These are chemical clocks, and they're found in every known being that has two or more cells and in some that only have one cell.
I'll give you an example -- if you take a horseshoe crab off the beach, and you fly it all the way across the continent, and you drop it into a sloped cage, it will scramble up the floor of the cage as the tide is rising on its home shores, and it'll skitter down again right as the water is receding thousands of miles away. It'll do this for weeks, until it kind of gradually loses the plot. And it's incredible to watch, but there's nothing psychic or paranormal going on; it's simply that these crabs have internal cycles that correspond, usually, with what's going on around it.
So, we have this ability as well. And in humans, we call it the "body clock." You can see this most clearly when you take away someone's watch and you shut them into a bunker, deep underground, for a couple of months. (Laughter) People actually volunteer for this, and they usually come out kind of raving about their productive time in the hole. So, no matter how atypical these subjects would have to be, they all show the same thing. They get up just a little bit later every day -- say 15 minutes or so -- and they kind of drift all the way around the clock like this over the course of the weeks. And so, in this way we know that they are working on their own internal clocks, rather than somehow sensing the day outside.
So fine, we have a body clock, and it turns out that it's incredibly important in our lives. It's a huge driver for culture and I think that it's the most underrated force on our behavior. We evolved as a species near the equator, and so we're very well-equipped to deal with 12 hours of daylight and 12 hours of darkness. But of course, we've spread to every corner of the globe and in Arctic Canada, where I live, we have perpetual daylight in summer and 24 hours of darkness in winter. So the culture, the northern aboriginal culture, traditionally has been highly seasonal. In winter, there's a lot of sleeping going on; you enjoy your family life inside. And in summer, it's almost manic hunting and working activity very long hours, very active.
So, what would our natural rhythm look like? What would our sleeping patterns be in the sort of ideal sense? Well, it turns out that when people are living without any sort of artificial light at all, they sleep twice every night. They go to bed around 8:00 p.m. until midnight and then again, they sleep from about 2:00 a.m. until sunrise. And in-between, they have a couple of hours of sort of meditative quiet in bed. And during this time, there's a surge of prolactin, the likes of which a modern day never sees. The people in these studies report feeling so awake during the daytime, that they realize they're experiencing true wakefulness for the first time in their lives.
So, cut to the modern day. We're living in a culture of jet lag, global travel, 24-hour business, shift work. And you know, our modern ways of doing things have their advantages, but I believe we should understand the costs.
Thank you.