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  • Narrator: Tails are like opinions.

    旁白:尾巴就像是意見 (每個人都有)。

  • Basically, everyone has them: fish, birds,

    基本上,大家都有尾巴:魚類,鳥類

  • most reptiles, and even some of our closest relatives.

    大多數爬蟲類,甚至是我們的近親。

  • So why are we missing out?

    那麼,為什麼我們的尾巴不見了?

  • Since tails first evolved at least 500 million years ago,

    自從 5 億年前有尾巴以來

  • they've taken on every role imaginable.

    它們就承擔了所有可以想像的角色。

  • Geckos use them to store fat.

    壁虎用它來儲存脂肪。

  • Birds use them to steer through the air,

    鳥類用它在飛行時掌控方向

  • and rattlesnakes use them to scare off predators.

    響尾蛇用它來嚇跑掠食者。

  • But for most mammals, they serve one major purpose:

    但是對於大多數哺乳動物來說,它有一個主要的功能:

  • balance.

    平衡。

  • Yet, as you get closer to humans on the evolutionary tree,

    然而,在進化成人類的過程中

  • tails disappear. Gorillas don't have them,

    尾巴消失了。大猩猩沒有尾巴

  • and neither do chimps or any other apes,

    黑猩猩或任何其他的猿類也沒有

  • including us, of course.

    當然,包括我們在內。

  • To understand why, take a look at how we walk.

    要了解原因,請看看我們如何走路。

  • Some of us primates crouch with our chest held diagonally

    有些靈長類動物是蹲著

  • to the ground. Others like gibbons and humans

    胸部傾斜地貼近面行走。 其他像是長臂猿和人類

  • can walk completely upright.

    可以完全直立行走。

  • Now, walking like this gives us a huge advantage

    這樣的走路姿勢,給我們帶來了莫大的好處

  • because unlike four-legged animals,

    因為不同於四條腿動物

  • which have to pour energy into every step they take,

    它們每走一步都必須耗費精力

  • two legs take advantage of gravity,

    兩條腿走路則可以利用地心引力

  • which does some of the work for us.

    地心引力減輕了一些我們走路的負擔。

  • You see, each time we take a step,

    你知道,每當我們邁出一步

  • gravity pulls us forward.

    地心引力就會拉動我們前進。

  • The end result is that when we walk,

    最終的結果是,當我們走路時

  • we use around 25% less energy than walking on all fours.

    我們使用的能量比用四肢走路要少 25%。

  • And in the wild, every ounce of energy you save

    在野外,你儲存的每一分能量

  • can mean the difference between survival and starvation.

    都可能是影響生存或飢餓的關鍵。

  • But this way of getting around also totally

    但這種走路方式

  • eliminates the need for a tail

    也完全除去了對尾巴的需求

  • because even though a human head

    因為即使一個人的頭部

  • weighs a hefty 5 kilograms,

    重達 5 公斤

  • it sits on top of the body when you walk,

    當你走路時,它是位在身體的最上方

  • not in front, so you don't need a tail as a counterbalance.

    而不是前方,所以你不需要用到尾巴來調節平衡。

  • Pretty disappointing, huh?

    很令人失望,是吧?

  • That being said, you can still see a reminder

    儘管如此,你仍然可以看到證據顯示

  • of a time when our ancient primate ancestors had one.

    我們古代的靈長類祖先,曾經有過這麼一段時間是有尾巴的。

  • Just look at a human spine.

    只要看看人類的脊柱就知道了。

  • You can see how the last few bones

    你可以看到脊柱最尾端

  • are partially fused together.

    非完整組合的幾塊骨頭。

  • That's your tailbone.

    這就是你的尾骨。

  • It's all that's left of our tail,

    我們的尾巴只剩下這些了

  • and, yes, it's sad and pathetic, and you can't wag it.

    沒錯,很可悲,而且你還不能搖它。

  • Now, in rare cases, babies are born

    在很罕見的情況下,嬰兒出生時

  • with what looks like a tail,

    長著像尾巴的東西

  • but that's not what's really going on.

    但那並不是真正的尾巴。

  • Most often, these tails are actually tumors,

    通常,這些尾巴實際上是腫瘤

  • cysts, or even a parasitic twin.

    囊腫,甚至可能是連體嬰。

  • Even more occasionally, they're a true

    更少見的是,它們是真正

  • outgrowth of the spine but are completely boneless,

    從脊柱長出來的,只是沒有骨頭

  • a soft tube made entirely of fat and tissue.

    是一種完全由脂肪和組織構成的管狀物。

  • These types of tails usually form as a birth defect,

    這些類型的尾巴通常是一種天生的缺陷

  • a deformity of the spine called spina bifida.

    是一種發生在脊柱的病變稱為脊柱裂。

  • And in these situations, doctors will surgically

    在這種情況下,醫生會在不傷害嬰兒的情形下

  • remove the tails with no harm to the baby.

    用手術將尾巴切除。

  • But as cool as it might sound to have an extra limb

    聽起來似乎很酷,我們多出了一肢,可以利用它

  • to swing through the trees or keep mosquitoes away,

    在樹上盪來盪去,或是驅趕蚊子

  • we are who we are today because, well, we don't.

    我們之所以成為現在的我們,因為我們沒有尾巴。

Narrator: Tails are like opinions.

旁白:尾巴就像是意見 (每個人都有)。

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B1 中級 中文 美國腔 尾巴 脊柱 靈長類 地心引力 脂肪 鳥類

為什麼人類沒有尾巴 (Why Humans Don’t Have Tails)

  • 112 8
    Liang Chen 發佈於 2021 年 01 月 14 日
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