wolves and coyotes have these big upright ears.

狼和土狼都有又大又直的耳朵

All the better to hear you with.

都是為了更清楚聽到你的聲音

But my dog Zeke here has floppy ears.

但我的狗奇克卻有下垂的耳朵

Why the difference?

為甚麼有不同呢?

Doesn't he need to hear too?

難道他們不用聽見聲音嗎?

Charles Darwin himself actually thought a lot about this question.

實際上，查爾斯‧達爾文對這個問題有很多想法

150 years ago, he published a book that said, "Look—it's not just pet dogs!”

一百五十年前，他出版了一本書叫“看，他不只是一隻寵物狗”

Pigs have floppier ears than wild boars.

豬的耳朵比野豬的下垂

Farmed goats have floppier ears than wild goats.

馴養的山羊比野生山羊的耳朵下垂

There are floppy-eared rabbits, cows and sheep.

有耳朵下垂的兔子、牛和羊

And that's not the only weird thing!

而這不是唯一奇怪的事!

Tame animals tend to have shorter snouts, and their fur tends to be paler

溫馴的動物往往鼻子較短，而且他們的皮毛通常顏色較淺

or have patches with color missing.

或沒有斑塊

All these mysterious traits put together have been called "domestication syndrome."

這些神秘的特徵被稱為“馴化症候群”

So, what's going on here?

所以，這裡發生了什麼？

The story starts thousands and thousands of years ago

這件事發生在成千上萬年前

when humans were surrounded by animals.

當時人類的周圍都是動物

Some animals were scary,

有些動物很可怕，

and some were a bit more approachable

有些平易近人的動物

even potentially useful.

甚至可能對人類有用

Our ancestors wanted them to be tamer, so sometimes

我們的祖先希望他們變得更溫馴，所以有時候

they tried breeding the friendliest ones.

他們嘗試繁殖出更友善的品種

At some point, strange side effects started to show up

在某些時候，奇怪的副作用開始顯現

Thousands of years later, good old Darwin noticed the domestication syndrome pattern,

幾前年後，達爾文注意到馴化症候群的模式，

but all he'd learned about change in the animal kingdom

但他所了解關於動物王國的變化

couldn't explain this connection between behavior and appearance.

無法解釋行為和外表之間的關聯

Scientists who came after him couldn't figure it out either.

在他之後的科學家也找不出來

But for the past few years, scientists have been throwing around a fascinating hypothesis.

但是在過去的幾年裡，科學家們已經拋出一個有趣的假設

They think the answer to this whole puzzle lies in a special group of cells.

他們認為這個難題的答案在於一群特殊的細胞

They're called neural crest cells, and coincidentally,

他們被稱為神經脊細胞，巧合的是，

they were discovered by Wilhelm His the exact same year Darwin published his book.

他們在達爾文出版他的書的同一年被威爾黑姆‧希斯發現

Neural crest cells show up very early in the development of all vertebrate embryos.

神經脊細胞在所有脊椎動物胚胎的早期就顯現出來了

As the embryo grows into a goat or a pig or a wolf,

隨著胚胎成長成山羊、豬和狼，

these special cells travel to every corner of the body

這些特殊的細胞會傳到身體的每個角落

and take on all sorts of different jobs.

承擔不同的工作

Now, here's the thing: Some of these cells end up right here above the kidneys.

現在重點來了，這些細胞中的一部分最終停在腎臟上方。

They become cells that secrete adrenaline

他們成為分泌腎上腺素的細胞

—that famous fight-or-flight hormone.

眾人所知的戰鬥或逃跑賀爾蒙

Wild animals are always fighting or fleeing to survive,

野生動物總是為了生存而戰鬥或逃跑

and that makes it hard for humans to get close.

使人類難以接近

But what if an animal was born with fewer of these neural crest cells,

但如果一隻動物出生時擁有比較少的神經脊細胞，

or those cells didn't work so well?

又或者這些細胞不能很好的運作呢?

That animal would have less adrenaline.

那隻動物就會擁有比較少的腎上腺素

It would probably be less freaked out by humans—

他可能比較不會被人類嚇到

and it would pass that behavior on to its offspring.

然後將這種行為傳遞給他的後代

The idea is that this is what's going on in domesticated animals.

這個想法是馴養動物正在發生的事

Their neural crest cells have been dialed back.

他們的神經脊細胞已經被奪回

And this would explain all the appearance stuff, too

這也可以解釋所有的外觀

because neural crest derived cells do a lot more than just make adrenaline.

因為神經脊細胞不僅僅是增加腎上腺素

Some of the cells end up forming parts of the face.

其中一些細胞最終形成臉的一部份

Some of them become cells that control the color of skin and hair.

其中一些成為控制皮膚和頭發顏色的細胞

And some make their way into the ears—and help make cartilage.

其中一些進入耳朵幫助生長軟骨

It's likely this is how dogs first got floppy ears.

這就是狗如何得到下垂的耳朵

And then centuries of intentional human breeding helped accentuate or reverse that change.

好幾個世紀的人類刻意地幫助突出和扭轉這個變化

But the neural crest cell hypothesis doesn't quite explain every bit of domestication syndrome.

但神經細胞並不能很好的解釋馴化症候群的每一點

Like—what's going on with other tame species that do have upright ears?

像為什麼其他溫馴的品種也有直立的耳朵

This be might be the excuse scientists need to spend more time with their pets.

這可能是科學家需要花更多時間陪他們的寵物的借口

This is Skunk Bear—NPR's science show

Please subscribe and check out some papers about the neural crest cell hypothesis

down in the description.