Name: 演化最強大的力量，正在你體內發生！| Sean B. Carroll (Evolution’s most powerful force is happening inside of you | Sean B. Carroll)
Uploaded: 2025-12-27T00:38:30.000Z
Duration: 13 min

Every day we are exposed to all sorts of potential pathogens.

我們每天都會接觸到各種潛在的病原體。

And by the time we're full grown adults, there are actually more bacterial cells living on and in our bodies than there are our own cells.

等我們長大成人時，我們體內外其實有比我們自身細胞還多的細菌細胞。

We've got to keep these in check or of course we'll suffer and potentially die.

我們必須控制住這些，否則當然會生病甚至死亡。

And our immune system operates on the very same principles of mutation and selection as evolution writ large does in the big world.

我們的免疫系統運作的原理，跟大世界裡宏觀的進化所依循的突變和選擇原理是一樣的。

Carroll, evolutionary biologist and author of several books, including my most recent, A Series of Fortunate Events, Chance and the Making of Planet Life and you the Evolutionary Process Within Us.

Carroll，一位進化生物學家，也是幾本書的作者，包括我最近的《A Series of Fortunate Events, Chance and the Making of Planet Life》以及《The Evolutionary Process Within Us》。

So evolution, what it really means is change over time.

所以，進化，它真正的意思就是時間的改變。

So we want to know how that change occurs over time.

所以我們想知道這種改變是如何隨著時間發生的。

And there's two dimensions to this process, and it kind of works like a staircase.

這個過程有兩個面向，有點像樓梯一樣。

And one process is mutation, and that's the rise in the staircase.

而其中一個過程是突變，這就像樓梯的上升。

If by chance that changes a property that favors reproduction, survival of the individuals, it will spread.

如果這種改變碰巧讓個體更有利於繁殖和生存，那麼它就會傳播開來。

And that's sort of the run in the staircase.

Chance invents and natural selection propagates that chance invention.

機會發明，而自然選擇則傳播這種機會發明。

And once that process has happened, new mutations can then be added on top of that, maybe even changing the character a little bit further.

一旦這個過程發生了，新的突變就可以疊加在上面，甚至可能讓特徵稍微改變得更多。

And that's another rise in the staircase.

And if that's working better, that's going to spread.

如果這樣做效果更好，那麼它就會傳播開來。

And so it's the cumulative set of mutations and the cumulative process of selection that takes us up that staircase.

所以，是突變的累積以及選擇的累積過程，帶領我們走上這階梯。

Now, here's something about the staircase of evolution that's very little appreciated.

現在，關於演化的階梯，有件事大家比較少注意到。

It's going on in every one of our bodies every day.

這件事每天都在我們每個人的身體裡發生。

And that's because our immune system works on the very same principles of mutation and selection as evolution writ large does in the big world.

這是因為我們的免疫系統，跟演化在大世界裡運作的原理一樣，都是基於突變和選擇。

像是細菌、病毒、真菌、寄生蟲。

And by the time we're full grown adults, there are actually more bacterial cells living on and in our bodies than there are our own cells, trillions and trillions of microbes.

等到我們長大成人，我們身體內外其實有比我們自身細胞還多的細菌細胞，數以兆計的微生物。

我們得要控制住牠們，不然當然就會生病甚至死亡。

And our immune system operates on the very same principles as the staircase of evolution.

而我們的免疫系統運作的原理，其實跟演化的階梯是一樣的。

And the most remarkable property our immune system is, it seems to be able to recognize as foreign virtually anything that can come at us out of nature, including entirely new pathogens that didn't even exist in the human population.

我們免疫系統最厲害的地方是，它好像能辨識出幾乎所有來自大自然的、對我們有害的東西，包括那些在人類族群中根本還不存在的全新病原體。

Well, it involves a process based on mutation and selection.

嗯，這涉及到一個基於突變和選擇的過程。

And the way this starts, I'll just describe it starting with a single cell.

我就從單一細胞開始描述這個過程吧。

所以你會有數十億個細胞，但是

these cells have different molecules on their surface that when they are complementary to molecules on the surface of a pathogen, they're activated, they're engaged.

這些細胞的表面會有不同的分子，當這些分子跟病原體的表面分子互補時，牠們就會被活化、被互動。

When engaged, they multiply very rapidly, such that over a period of about a week, one cell may become billions of cells and start to pump out large quantities of chemical weapons known as antibodies that thwart that invader.

被互動後，牠們會快速增殖，大約一週的時間，一個細胞就可能變成數十億個細胞，然後開始大量分泌稱為抗體的化學武器，來擊退入侵者。

These billions of cells of our immune system are actually clones, Clones that are subtly distinct from each other, that have unique ability to recognize something else.

我們免疫系統的這數十億個細胞，其實是複製體，這些複製體彼此之間有細微的差異，擁有辨識其他東西的獨特能力。

Now, that something else could be any variety of things on an invading pathogen.

而這個「其他東西」可能就是入侵病原體表面的各種東西。

But once they recognize that, that clone gets amplified, can grow to be many, many, many cells in the course of a week or so.

不過一旦辨識出來，這個複製體就會被放大，在一週左右的時間內，可以變成非常非常多的細胞。

That first wave of defense is decent, but not optimized.

第一波的防禦還算不錯，但還不夠完善。

There's actually a mechanism to make those chemical weapons, the antibodies, that cell makes even more potent, even more deadly to essentially the invading pathogen.

事實上，有個機制能讓細胞製造的化學武器——抗體——變得更強大、更致命，來對付入侵的病原體。

And that's because there's a specific genetic mechanism that mutates the antibody encoding genes, leaves the rest of the genes in the body alone, but

這是因為有個特殊的基因機制，會突變抗體的編碼基因，身體其他基因則不受影響，但

just the antibody genes start undergoing a process called hypermutation and therefore generating all sorts of antibody variants.

只有抗體基因會開始經歷一個叫做「超突變」的過程，進而產生各種抗體變異體。

And the antibody variants that recognize the pathogen better are selected for.

而那些能更好地辨識病原體的抗體變異體，就會被選擇下來。

So this hypermutation process, we now select antibodies, and

所以這個超突變過程，我們現在選擇抗體，然後

this can go through various cycles to make ever better and better antibodies.

這個過程可以經歷好幾個循環，做出越來越好的抗體。

So we're really zeroing in on this particular pathogen.

所以我們真的鎖定了這個特定的病原體。

So late in immune response, say, for example, the second week you're recovering from a flu virus, your immune system is ever more potent, ever more more.

在免疫反應的後期，比方說，你從流感病毒康復的第二週，你的免疫系統會變得越來越強大。

Ever more powerful in defeating its enemy because it's up that staircase.

在擊敗敵人方面變得越來越強，因為它已經爬上那個階梯了。

Eventually, a staircase sort of splits and some cells are set aside.

最後，階梯會分岔，有些細胞會被保留下來。

They're there to be used when this pathogen is encountered again.

牠們在那裡，以便在再次遇到這個病原體時被使用。

Other cells continue to make the antibodies.

Y' all are familiar with a phenomenon where, for example, you.

大家應該都聽過一個現象，例如，你。

You don't get measles twice, you don't get chickenpox twice, et cetera.

你不會得兩次麻疹，也不會得兩次水痘，諸如此類的。

Why is this immunological memory that even if 50, 60, whatever number of years ago you might have been exposed to that virus, your immune system is still poised to attack it again if you're exposed again.

為什麼會有這種免疫記憶，即使在 50、60 年，甚至多少年前你可能接觸過那個病毒，你的免疫系統仍然隨時準備好，在你再次接觸時再次攻擊它。

This system is called adaptive Immunity, much like the process of evolution, of mutation and selection, is adapted.

這個系統叫做適應性免疫，就像進化、突變和選擇的過程一樣，是適應的。

It really only exists in this form in animals with backbones, long lived, generally larger animals.

它確實只存在於有脊椎動物、長壽、通常體型較大的動物身上。

And you can see its utility because the longer your lifespan, the greater the chance you're going to re encounter a particular pathogen.

你可以看到它的用處，因為你的壽命越長，你就越有可能再次遇到某種病原體。

If you're a short lived mayfly or something like this, you don't live long enough to see the same thing twice.

如果你是像蜉蝣那樣短命的生物，你活不到能看到同樣東西兩次。

So lots of animals, including, you know, simpler things like worms and flies and all that, they have what we call innate immunity.

所以很多動物，包括你知道的，像蠕蟲、蒼蠅等等比較簡單的生物，牠們有我們稱之為先天免疫的東西。

They have ways that sort of put barriers up against pathogens.

牠們有辦法對病原體設下屏障。

But this adaptive immunity only exists in creatures with backbones, with vertebrates.

但這種適應性免疫只存在於有脊椎的生物，也就是脊椎動物身上。

And it's pretty elaborate in, in us, in, in mammals, animals with fur, etc.

而且在我們、哺乳類動物、有毛的動物等等身上，它相當精緻。

But it's pretty well developed even in things like fish and sharks inside our bodies.

但在像魚類和鯊魚這類生物體內，它發展得相當好。

The timescale of this process is very, very fast.

這個過程的時間尺度非常非常快。

It's more like what we described with respect to microbes, because it starts with cells and cells that can multiply pretty frequently.

這比較像是我們之前描述的關於微生物的狀況，因為它開始於細胞，而這些細胞可以相當頻繁地增長。

So a lot of evolution can take place in a short time.

所以很多進化可以在短時間內發生。

Most of us are sort of familiar that, you know, most infections don't knock us down for more than about a week.

我們大多數人都大致知道，你知道的，大多數感染不會讓我們倒下超過一週左右。

That's when our immune system eventually sort of catches up and overtakes the pathogen.

那時候我們的免疫系統終於追上並壓制了病原體。

So that gives you a sense of the timescale it takes to mount the response, expand that response to the point where it overwhelms the pathogen.

這讓你對啟動反應所需的時間尺度有個概念，將反應擴大到足以壓倒病原體的程度。

Whereas out there in the world, sort of a battle between predator and prey or whatever, that may go on for hundreds of thousands of years before there's sort of a winner, same process, much more rapid timescale in your body.

然而，在外界，像是掠食者和獵物之間的戰鬥，或是其他等等，可能要經過數十萬年才能分出勝負，這個過程是一樣的，但在你的身體裡，時間尺度快得多。

How is it possible that we can recognize virtually anything that the world will throw at us?

究竟我們是怎麼辦到，能夠辨識得了世界上丟給我們的任何東西的呢？

And fundamentally, one of the problems there is sort of a coding problem.

根本上，其中一個問題是個編碼問題。

How can one make all the different kinds of antibodies that could recognize all the different possible pathogens that a species might encounter?

要怎麼做出各種不同抗體，來辨識一個物種可能遇到的所有不同病原體呢？

The solution to that required understanding how antibody genes are encoded in DNA, something we weren't able to do until the 1970s or so.

這個解決方案需要理解抗體基因是如何在 DNA 中編碼的，這在 1970 年代左右我們才辦得到。

What that's revealed is that we mix and match pieces of antibodies in a way that we can generate com millions of combinations of antibodies.

這揭示了我們透過混合搭配抗體的片段，能夠產生數百萬種抗體的組合。

And it's now estimated that we may be able to make about 10 billion different antibodies.

現在估計我們可能可以製造大約 100 億種不同的抗體。

And you might go, well, that sounds sort of impressive, but okay, well here's the thing.

你可能會說，嗯，聽起來很厲害，但好吧，事情是這樣的。

In our entire genome, all of our DNA, we only have about 20,000 genes.

在我們整個基因組，所有的 DNA 中，我們只有大約 20,000 個基因。

So how do you make 10 billion antibodies when there's only 20,000 genes to begin with.

那要怎麼在最初只有 20,000 個基因的情況下，製造出 100 億種抗體呢？

And this is the brilliant trick of the immune system.

It makes antibodies from short little gene segments that it mixes and matches in millions, if not billions of combinations.

它會從短小的基因片段製造抗體，並以數百萬種，甚至數十億種組合方式進行混合搭配。

So the trick of combinations is that it's just like in a, you know, if you can take a deck of cards, right, and

組合的巧妙之處就在於，就像你從一副撲克牌裡抽牌一樣，

you have, you know, five cards, you draw from a deck, there's lots and lots of different combinations.

你抽出的五張牌，可以有很多很多不同的組合。

You can, even if you have only 52 different cards from a modest number of antibody genes on the order of a few hundred, by mixing and matching them in pieces, we can generate enormous numbers of antibodies.

即使你只有幾百個抗體基因，透過將它們的片段混合搭配，我們就能產生龐大的抗體數量。

The immune system, even with all its powers, can still be beat to the punch.

免疫系統，即使擁有所有這些力量，仍然可能被擊敗。

There's still pathogens that can kill us, and this is why we vaccinate.

還是有病原體會殺死我們，這就是我們接種疫苗的原因。

And we understand in vaccines generally what we're giving is a little component, usually a non living component, not the virus itself, not the pathogen itself, but

而我們通常知道，疫苗裡給予的是一個小部分，通常是非活體的部分，不是病毒本身，也不是病原體本身，而是

maybe just a molecule that represents that pathogen.

也許是一個代表該病原體的分子。

And we're using that to prime the immune system.

我們利用它來預先啟動免疫系統。

So we're activating the immune system so it goes through some of those steps on the staircase, establishes memory, and

所以我們活化免疫系統，讓它走過樓梯上的某些步驟，建立記憶，然後