Name: 私たちは死ぬようにプログラムされているのか？老化の本当の科学 (Are We Programmed to Die? The Real Science of Aging)
Uploaded: 2025-08-20T11:44:56.000Z
Duration: 7 min 30 s
Description: VoiceTubeの動画で発音を聞きながら英語表現を覚えよう！学べる英語：

So so I heard long ago and I checked it out and I think it's true that all mammals live for about the same number of heartbeats, except for humans who live two or three times that

昔聞いた話なんだけど、調べてみたら、すべての哺乳類がほぼ同じ鼓動数で生きているというのは本当だと思う。ただし、人間はその2倍も3倍も生きている。

程度の副詞

Except, if you go back far enough in time when we were just living in caves, we were right with all the rest of the mammals.

So first, is that true? Second, there are animals, not mammals, that live much longer than we do. I'm thinking of the Galapagos tortoise, for example.

Yeah, so do you guys study other animals to get insight?

それで、あなたたちは他の動物を研究して知見を得るんですか？

So there is a whole field devoted to looking at lifespan of different species.

少なくとも哺乳類の間では、心臓の鼓動の回数がほぼ同じであることを、『scale』という本を書いたジェフリー・ウェストが示しています。それは、小動物の方が代謝率が高いという事実と関係があります。

And you are right that at least among mammals, a Jeffrey West, who's written a book called Scale, shows that the number of heartbeats is roughly the same.

That has to do with the fact that smaller animals have a higher metabolic rate. They have a faster metabolism and and they almost need to because their surface-to-volume ratio is larger.

We did a whole explainer on surface-to-volume ratio.

私たちは体表面積比について一通りの解説をしたし、だから彼らはより高い代謝率を維持する必要がある。

And so they they they need to maintain a higher metabolic rate. That's one of the reasons that's only one of the reasons why they have higher heart rate That's not a reason why they should die sooner.

Ah, the why we should die die sooner is has an evolutionary Explanation and that is Evolution doesn't care how long you live.

ああ、なぜ私たちが早く死ぬべきなのかというと、進化論的な説明がある。

It only cares about fitness fitness in the biological sense is the likelihood that you're going to be able to Successfully pass on your genes and people always misinterpret that as being physically fit or stronger or whatever I will love the fittest.

生物学的な意味でのフィットネスとは、自分の遺伝子をうまく受け継ぐことができるかどうかの可能性のことで、人々はいつも、身体的にフィットしているとか、より強いとか、そういうことだと誤解する。

Yeah, George should have found a different word So evolution cares about fitness now at the same time for most of our history and Certainly the history of all other species resources are limiting and so You have to select do you put more of your resources into maintenance and repair of the individual?

そう、ジョージは別の言葉を使うべきだったのだ。だから進化はフィットネスを重視する。

Animal or do you put it into growth and reproduction?

それとも成長と生殖に使うのか？

There's always a balance if you if you have limited energy So in the case of a mouse, which lives about two years in the wild There's no sense in having a mouse live for 40 years because long before that it's going to be eaten.

エネルギーに限りがある場合、常にバランスが必要だ。野生のネズミの場合、2年ほど生きる。

Yep, exactly Or it'll die of starvation or a drought or something And so in the case of a mouse evolution has favored selection of a species that grows very quickly and reproduces prolifically That's a mouse if you get to a large animal like a bowhead whale Let's take an even even bigger than an elephant They can live for two three hundred years and they have a very relatively slow metabolism Wow, and even slower metabolism is not a mammal, but it's still a vertebrate called the Greenland shark 700 years Yeah a vertebrate living for 700 years very slow metabolism How do you know that?

マウスの場合、進化は非常に早く成長し、繁殖する種を選択することを優先した、さらに代謝が遅いのは哺乳類ではないが、グリーンランドシャークという脊椎動物だ。

We didn't even have marine biology 700 years ago They can do things like carbon dating and they cut one open it was a 700 rings So you've got the mayfly lives a day mayfly lives a day right and then between that you've gone from there to a Greenland shark And you're Galapagos and there are actually other animals that are thought not to even age Biologically, what's the emote like a hydra and the immortal jellyfish these things have an actual animal called the hydra.

700年前には海洋生物学すらなかったんだ。炭素年代測定のようなことができるんだけど、1匹を切り開いたら700個のリングだった。だから、カゲロウの寿命は1日なんだ。カゲロウの寿命は1日で、その間にグリーンランドシャークや、ガラパゴスや、生物学的には年を取らないと考えられている動物が他にもいる。

No This is a freshwater small animal and okay, they're full of stem cells, so they're constantly regenerating themselves But if you followed an individual it would also age only very slowly.

でも、もし個体の老化を追跡したら、非常にゆっくりとしか老化しないだろうね。

It's just in the wild It it dies for other reasons before Actually aging.

ただ野生では、実際に老化する前に他の理由で死んでしまう。

だから、今はいろいろな種類がある。

Here's might be the only species That dies of natural causes in the world.

世界で唯一、自然死する種かもしれない。

つまり、頂点捕食者の可能性があるということだ。

だから、そうかもしれないね。

In fact, there's a book Written by Steven Ostad called Methuselah zoo Which way talks about all these animals in this book.

実際、スティーブン・オスタッドが書いた『Methuselah zoo Which way』という本がある。

He he points out Methuselah zoo in Methuselah zoo he points out how all these species have such different lifespans and It's because of this evolutionary selection, but it's actually worse than that It's the fact is evolution will select for things that help you early in life Even if they cause a problem later in life So many of the things that cause aging are related to growth For example or to cancer prevention, you know prevention of or the or senescent cell These things all help us early in life and they're there a problem later in life But evolution doesn't care what happens to you when later we're not making babies.

彼はメトシェラ動物園で、これらの種がいかに寿命が違うかを指摘している。 それは進化的淘汰のせいだが、実はそれよりも悪いことがある、例えば、癌の予防、老化細胞の予防などだ。これらのことはすべて、人生の初期には役に立つが、後年になって問題になる。

Yeah, exactly Yeah, because that's the whole deal So what helps us survive in infancy and then go on to reproduction is the key component of our decline and demise not always not Okay, there are things that happen to us early in life that are selected for early in life that cause aging So the real deal is just keep having babies your entire life And then you you'll never age.

そう、その通りだ。乳幼児期を生き延び、生殖に向かうために必要なことが、私たちの衰えと終焉の重要な要素なのだ。

However, you will eventually kill yourself because of these kids So we're we're an outlier we're an outlier we live about twice as long twice as we would Based on our size, but only post caveman life, right?

しかし、この子供たちのせいであなたはいずれ自殺することになる。だから、私たちは異常者なのだ。私たちは、私たちの体格を基準にすると、約2倍長生きするが、原始人以降の人生だけだろう？

So only I mean half of everyone died by 30 Yeah, and so we're not 2x other mammals at our size Yeah, and one last thing is there's a group of animals mammals the bats They live much longer they're about the same size as a mouse in terms of mass Yeah, if leader mouse, they they they live about 10 or 20 times as long as a mouse Mm-hmm, and the reason is they can fly around So that means two things they can escape predators more easily Yeah, and they can also forage over a much wider area for food So and and when they roost their roost in the ceilings of caves, so they're not safe accessible They've been designed to survive longer And so there is worth it for evolution to make them live longer because they'll still keep producing more babies Yeah, so you got to be grandpa Munster.

だから、30歳までに死んだのは全体の半分だけで、他の哺乳類の2倍もいないんだ。最後にもうひとつ、哺乳類にはコウモリという動物がいる、ねぐらは洞窟の天井をねぐらにするから、安全な場所には近づけないんだ 長生きするように設計されているんだ 長生きさせることは進化にとって価値があるんだ なぜなら、より多くの赤ん坊を産み続けることができるから そう、だからマンスターじいさんになるんだ