What shape is an egg?

蛋是什麼形狀的？

Chances are you're picturing this: It's generally round, a little fatter at one end, and it probably came out of the non-clucking end of a chicken.

你很可能在想這個：基本上就是圓圓的、有一端比較平，而且大概是從雞不會咯咯叫的那一端跑出來的。

The chicken egg is the egg that most of us know, which makes sense considering there's 2.5 chickens for every person on Earth, they're what most of us eat, and we've been indoctrinated with them from a young age.

雞蛋是我們大多數人熟知的蛋，有道理，畢竟地球上有一人就有 2.5 隻雞，它是我們大多數人的食物，從小就養成這種概念。

"This is just a plastic chicken egg."

「這只是一顆塑膠蛋。」

(Hatching noises)

(孵化聲)

But is this shape really "egg-shaped"?

但這個形狀真的是「蛋形」嗎？

In 2017, scientists analyzed the shape of nearly 50,000 eggs from 1,400 different bird species, and plotted them based on how elliptical–or squished–they are, and how pointy–or asymmetrical–one end is.

在 2017 年，科學家分析了來自 1400 種鳥禽、5 萬顆蛋的形狀，並且依照橢圓 —— 或說擠壓 —— 程度以及某端的尖頂程度 —— 即不對稱 —— 繪製圖表。

And chicken eggs are outliers.

雞蛋是其中的特例。

Most bird eggs aren't shaped like this.

大多數鳥蛋的形狀不是這樣。

Bird eggs come in many shapes.

鳥蛋有各種形狀。

Nearly spherical eggs like owls, pointy cone eggs of shorebirds like the common murre, even the tiny tic-tac eggs of hummingbirds… and everything in between.

貓頭鷹的蛋形幾近球狀，水鳥 (例如海鴉) 蛋形尖筒狀，即便是蜂鳥小不嚨咚的蛋 …… 也長不一樣。

Scientists have been wondering for a long time how and why all of these different egg shapes came to be.

科學家納悶很久了，為什麼這些蛋會有各自不同的形狀。

But before we inv-egg-stigate those questions, let's take a minute to appreciate just how eggcellent eggs really are.

不過在我們深入蛋裡研究前，我們先花點時間欣賞蛋有多棒。

Dad yolks, gotta love em.

蛋黃呀，愛死了。

More than 350 million years ago, the ancestors of every land-dwelling, backbone-having animal alive today began to crawl out of the water, and they pretty quickly colonized every terrestrial habitat on Earth.

超過 3 億 5000 萬年前，陸上生物 —— 今日的脊椎動物 —— 的祖先從水裡爬出，很快就稱霸了地球上所有陸上棲地。

And one evolutionary innovation made that possible more than any other: Eggs with shells.

這要歸功於一項演化創新：有殼的蛋。

Although many other animals lay eggs, the evolution of the shell allowed reproduction away from BLEEP environments.

雖然其他很多動物也會生蛋，不過演化出蛋殼讓牠們得以脫離 ** 環境繁殖。

Wait.

等等。

I can't say BLEEP (moist)?

我不能說 ** (濕潤)？

I guess I don't wanna get demonetized, so…

我也是不希望被禁，所以 ……

Eggs with shells allow reproduction away from wet environments.

有殼的蛋讓生物得以脫離潮濕環境繁殖。

These self-contained life-support systems keep everything inside from drying out, and it meant that reptiles and the early ancestors of mammals could travel, see the world, set up shop in every corner of Pangaea.

這些自成一套的維生系統能防止內容物乾掉，意味著爬蟲類以及哺乳類的祖先能夠長途跋涉、探索這個世界，在原始大陸的各地駐扎。

The ancestors of mammals eventually moved all the egg and baby-growing business inside our bodies–except for these weirdos.

哺乳類的祖先最終將所有蛋和寶寶生長過程搬進我們的身體裡，除了這些小怪咖。

So many questions.

太困惑了。

While reptiles from crocodiles to turtles to snakes to dinosaurs stayed in the egg business.

不過鱷魚和烏龜和蛇以及其他爬蟲類依舊繼續下蛋。

Reptile egg shells range from leathery to hard, but one special branch of the dinosaur family tree eventually took natural shell-ection to the next level: Birds.

爬蟲類的蛋殼有皮質的也有非常堅硬的，不過恐龍家族在今日的其中一條分支又將大自然的蛋殼提升到另一個境界：有請鳥類。

What makes a bird egg so eggstra cool is this hard shell.

鳥蛋特別厲害的在於它的堅硬外殼。

It's strong enough that this many eggs can support my full body weight without breaking.

它的堅硬程度足以在這個數量下支撐我全身的重量而不會破裂。

I'm standing on two dozen eggs.

我站在兩打蛋上。

They said it couldn't be done!

他們說不可能！

I'm so afraid to move.

我不敢移動。

And that strength comes from the shell's shape.

力量來自於蛋殼的形狀。

If you watched my video about the science of igloos, you remember that this shape, called a catenary arch, distributes tension and compression more evenly than a half circle shape.

如果你看過我講冰屋科學的那集，你會知道這種形狀叫做垂曲線拱形，比起半圓形更能夠分散張力和壓力。

Along with the microscopic protein and mineral nanostructures in the shell, this shape makes egg stronger than it would be if it was another shape.

在加上蛋殼裡顯微鏡下的微小蛋白質和奈米構造，這個形狀比其他任何形狀更能提供鳥蛋力量。

This brings me back to our original question: What is an egg's shape?

這把我們帶回到最初的問題：蛋是什麼形狀？

An oval is a 2-dimensional curve whose name literally means "egg-shaped".

「橢圓形」(oval) 指的是一個二維的曲線，字面意思即是「蛋形」。

Unlike an ellipse, there's no exact geometric definition for an "oval", but they can be constructed by joining other arcs of different radii.

不同於「橢圓」(ellipse) ，oval 沒有一個既定的幾何學定義，但能藉由連結兩個不同半徑的弧形構成。

They generally only have one axis of symmetry, and by rotating an oval along this axis, the surface of revolution we create is called an "ovoid".

他們通常只有一個對稱軸，以這根對稱軸為中心旋轉，旋轉面所形成的就稱為「卵型」。

That's "egg-shaped"… at least according to math.

也就是「蛋形」，至少數學是這樣說的。

But while the shell gives this shape strength, the shell doesn't make the egg egg-shaped.

雖然蛋殼給這個形狀支撐力，蛋殼卻不是讓蛋形成蛋形的原因。

If you dissolve away an egg shell, which is rich in calcium carbonate, with an acid, like vinegar, it maintains its shape.

如果你用酸性物質，比如醋，將蛋殼表面的碳酸鈣溶解，它還是會維持它的形狀。

The "egg shape" isn't caused by the shell.

「蛋形」並不是蛋殼所造成。

It's caused by this squishy inner membrane.

而是來自於軟趴趴的內膜。

It starts with an unfertilized egg cell, added to a blob of yolk, and squeezed down a stretchy tube called an oviduct.

它始於一顆未受精的單細胞，裡頭有一小點蛋黃，被一條稱為輸卵管的彈性管子擠壓。

As it travels it's fertilized by sperm, wrapped in those membranes and inflated with fluid like a balloon.

當它被精子受精，就會被那些膜包裹然後充滿液體、像氣球一樣鼓起來。

The shape of the egg is determined when those membranes form.

蛋的形狀在那些膜形成時就一定確定了。

Over the years scientists have had a lot of hypotheses about why different birds create eggs of different shapes.

幾年來科學家針對為何不同種鳥產不同形狀的蛋有許多假設。

One hypothesis is the more spherical the egg, the less shell material it takes to cover.

一個假設是蛋越趨球狀，它需要的蛋殼成分就越少。

Another is, depending on how many eggs a mother lays, different egg shapes could snuggle better during incubation.

另一個假設是，取決於鳥媽媽生多少蛋，不同的蛋形能夠在孵蛋過程依偎得更緊密。

Or maybe birds that are born ready to walk and feed themselves might grow better in one shape versus another.

或也許孵出來就能獨立自足的鳥在某種特定的蛋形中會長得更好。

And for birds that nest on cliffsides, pointier eggs tend to roll in circles instead of rolling off the edge.

對那些在懸崖上築巢的鳥而言，尖型的蛋會原地打轉，而不會掉下去。

These are just a few of the possible answers people came up with.

這些只是幾個人們想出來可能的解答。

But when those scientists from earlier analyzed thousands of egg shapes from across different families of birds, the best correlation they found was between shape and flying ability.

不過當那些科學家研究不同鳥蛋的蛋形時，他們發現了蛋形和飛行能力的關聯性。

Birds that are better fliers have more streamlined bodies, and their organs are more tightly packed, which puts a limit on how wide an egg you can squeeze through that egg-making tube.

擅於飛行的鳥類身形偏流線型，牠們的器官也裝得比較擠，這也就限制了產道能容納的蛋大小。

Inside a computer, those scientists were even able to virtually form every egg shape we know of by changing just two things: the stretchiness of the membrane and how it's squeezed.

那些科學家甚至能夠用電腦模擬所有已知的蛋形，只需要改變兩個因素：膜的延展性，以及它被擠壓的方式。

The most common egg shape among all birds is something closer to this.

縱觀所有鳥類，最常見的蛋形是這種。

A little pointier than our so-called "typical" chicken egg.

比我們一般熟知的雞蛋要尖一點。

Trust me, they're different.

相信我，它們不一樣。

They measured.

他們可是量過。

Thinking about it in the eyes of eggvolution, it's not that pointy eggs give acrobatic birds an advantage, it's just a natural consequence of having a narrow body.

想想演化論，並不是尖頭蛋給了這些在空中表演特技的鳥優勢，這是他們較窄的身形得來的自然結果。

And we do know the first dinosaurs that laid pointy eggs were the group that gave rise to birds.

我們知道首先開始產尖頭蛋的恐龍是鳥的祖先。

But here's one important thing to remember about how evolution works: Body shape might be the best answer when we look at all birds, but that doesn't mean it's the only answer.

不過說到演化論運作的方式，有很重要的一點要記得：當我們看所有的鳥，身形或許是最佳解答，但並不是唯一。

Different families of birds might get different evolutionary eggvantages from different shapes.

不同種的鳥或許藉由不同形狀的鳥蛋獲得演化優勢。

Even if a bird's body isn't that skinny, maybe a pointy egg really does keep it from rolling off the edge of a cliff, or make it easier for the parents keep it warm.

即便一隻鳥的身體並不是真的那麼纖細，尖頭蛋或許的確起到防止掉落懸崖的作用，或是讓它爸媽更容易孵蛋。

Natural selection can happen on many levels, and there can be evolution inside of evolution.

大自然的篩選可能發生在各種層面，演化論的裡頭或許又有演化論。

So, are all eggs egg-shaped?

所以，所有蛋都是蛋形嗎？

Well, you could say "egg-shaped" just means whatever shape an egg is.

嗯 …… 你是可以用蛋形泛指蛋的各種形狀。

But that's not a very satisfying answer.

但這個答案差強人意。

What it means to me is… there is no egg-shape, because nature's made so many different shapes, for different reasons.

我覺得應該說 …… 根本沒有蛋形這回事，因為大自然創造了那麼多種蛋的形狀，原因各不相同。

In the end, the question of why different birds lay different shaped eggs isn't settled.

到頭來，為什麼不同種的鳥產不同種的蛋還沒有個定論。

And that's ok.

但也沒關係。

Because that's how science works.

因為科學就是這麼回事。

If it was wrapped up with a neat little bow, we wouldn't have any questions left to incubate, and no new ideas left to hatch.

如果這個問題簡單直觀，那就沒什麼問題好孕育，沒有新點子可以孵化。

Stay curious.

永保好奇。