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  • We have lots in common with our closest primate relatives.

    譯者: 子容 黃 審譯者: Amanda Zhu

  • But comparatively, humans seem a bit... underdressed.

    我們與其他靈長類近親有許多共同點。

  • Instead of thick fur covering our bodies,

    但相對而言,人類穿著 似乎有些……單薄。

  • many of us mainly have hair on top of our heads

    我們沒有厚重的毛髮覆蓋身體,

  • and a few other places.

    毛髮主要集中在我們的頭頂

  • So, how did we get so naked? And why do we have hair where we do?

    和其他幾個地方。

  • Human hair and animal fur are made of the same stuff:

    我們是怎麼變得這麼光禿禿的? 我們的毛髮又為何會長在那些地方?

  • filaments of the protein keratin that grow out of organs known as follicles,

    人類毛髮和動物毛 是由同樣的材料做成的:

  • which go through cycles of growth and shedding.

    從稱為毛囊的器官中長出,

  • Across mammalian species, hairs have been modified for numerous purposes,

    經歷生長和脫落循環的角蛋白絲。

  • ranging from the soft fluff covering rabbits

    哺乳動物中,毛髮已演化出多種用途,

  • to the rigid quills protecting porcupines.

    從覆蓋兔子的柔軟絨毛

  • But for many mammals, hair grows in two layers

    到保護豪豬的硬刺。

  • consisting of a shorter undercoat of ground hairs

    許多哺乳動物的毛髮生長為兩層,

  • covered by longer guard hairs.

    由較短的毛作為底層毛髮,

  • Together, they help insulate the animal’s body and protect its skin.

    上面覆蓋較長的保護毛。

  • Human hairs, on the other hand, are kind of a combination of these hair types.

    它們一起幫助動物的身體 與外界隔絕並保護其皮膚。

  • Unfortunately, hair is rarely found in fossils,

    另一方面來說,人類的毛髮 綜合了這些類型的毛髮。

  • making it hard for researchers to pinpoint when and how

    不幸的是,化石中鮮少發現毛髮,

  • our ancient ancestors lost their coats.

    使研究人員很難確定古代的祖先

  • But scientists have developed some working hypotheses.

    在何時以及如何失去他們的外衣。

  • It seems that, millions of years ago in Africa,

    但科學家們已提出一些現行的假說;

  • early hominins first transitioned out of trees and adopted a more active lifestyle.

    似乎在數百萬年前的非洲,

  • Keeping cool became increasingly important.

    早期的古人類從樹居 轉型為活動性較高的地面生活,

  • Eventually, they developed more sweat glands,

    因此保持涼爽變得越來越重要,

  • which helped them lose heat by evaporating moisture through the skin.

    於是,他們發育出更多的汗腺,

  • In fact, humans have 10 times more sweat glands than chimpanzees, for instance.

    以幫助他們透過皮膚蒸發水分來散熱。

  • But efficiently losing heat by sweating is harder to do when youre covered in fur.

    事實上,舉黑猩猩為例, 人類的汗腺數量是它的 10 倍。

  • Scientists believe that early humans lost much of their coat around this time

    但是當你被毛皮覆蓋時, 很難透過出汗有效地散熱。

  • to help their sweat evaporate faster.

    科學家認為,早期的人類 在這個時期失去了大部分毛髮

  • However, if losing our hair was so advantageous,

    來讓汗水蒸發得更快。

  • why do we have any left at all?

    然而,如果脫毛有如此好處,

  • It seems that there are unique uses for hair in different parts of our bodies.

    我們為什麼還留著一些呢?

  • When it comes to the tops of our heads,

    我們身體不同部位的毛髮 似乎都有其獨特的用途。

  • temperature regulation likely played a part again.

    說到我們頭頂時,

  • Since early humans began venturing into the open,

    溫度調節似乎又是個重點。

  • their heads wouldve been exposed to the scorching sun.

    自早期人類開始進入 沒有樹木遮蔽的地區以來,

  • Thicker, longer-growing hair protects our sensitive scalps

    他們的頭部就會暴露在烈日下。

  • and keeps our brains from overheating.

    長而濃密的頭髮 可以保護我們敏感的頭皮,

  • Dark tightly curled hair is most effective at keeping solar radiation off of skin.

    並避免我們的大腦過熱。

  • Other kinds of head hair evolved as humans moved to different places.

    深色且極為捲曲的頭髮 最能有效地防止太陽輻射照射皮膚。

  • Meanwhile, researchers think eyebrows are especially useful for communication

    人類移居不同的地方時, 也演化出不同類型的頭髮。

  • because they sit atop active facial muscles that convey our feelings.

    同時,研究人員認為眉毛 特別有助於溝通,

  • Eyelashes have been shown to minimize airflow over our eyeballs,

    因為它們位於表達 我們感受的面部肌肉上。

  • preventing them from drying out and catching debris.

    已有證據顯示睫毛可以 使我們眼球上的氣流降到最低,

  • And maybe facial hair proved helpful in distinguishing identity from a distance,

    避免眼球乾燥並防止雜質進入。

  • but we really don’t know.

    也許鬍子有助於從遠處分辨身份,

  • Evidence is stubbly at best.

    但我們其實不確定。

  • Why we have hair in other regions is... more pungent.

    證據過於粗淺。

  • Our armpits, nipples, and pubic areas are dotted with apocrine glands.

    為什麼我們在其他部位 有毛髮的問題就更……辛辣了。

  • They produce oily, smelly secretions which the thick, curly hair

    我們的腋窩、乳頭和陰部 分佈著頂泌腺,

  • that often grows in these spots helps disperse.

    它們會產生油膩有臭味的分泌物,

  • The secretions that waft off these hairy patches may be useful for identification.

    通常長在這些部位上的濃密捲髮 有助於散播這些分泌物。

  • For example, several studies have shown that people are able to identify

    從這些毛髮部位飄出的分泌物 可能有助於識辨身分。

  • their own armpit odors as well as those of people theyre close with.

    舉例來說,多項研究顯示

  • The final type of notable human hair is the vellus hair that covers our bodies.

    人們能夠識別自己 以及親近的人的腋窩氣味。

  • We don't know if these hairs serve any purpose themselves,

    最後一種值得一提的人類毛髮是 覆蓋我們身體的毳毛。

  • but the follicles vellus hair grows from are essential banks of stem cells

    我們不知道毳毛是否有任何用途,

  • that repair damaged skin after injury.

    但從長出毳毛的毛囊 是重要的幹細胞庫,

  • Theyre also important sites of nerve endings that convey signals

    能修復受傷的皮膚。

  • of gentle touch to the brain.

    它們也是神經末梢所在的重要部位,

  • In fact, although it’s much finer,

    向大腦傳遞溫柔觸摸的信號。

  • humans have roughly the same density of body hair as apes of comparable sizes.

    事實上,儘管人類毛髮比人猿細得多,

  • So despite all this talk of human nakedness,

    但人類的體毛密度 與體型相當的人猿幾乎相同。

  • we're not actually as hairless as we look.

    所以儘管有這麼多人類赤裸的說法,

We have lots in common with our closest primate relatives.

譯者: 子容 黃 審譯者: Amanda Zhu

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B2 中高級 中文 美國腔 TED-Ed 毛髮 人類 部位 覆蓋 皮膚

人類身上沒有很多毛髮的原因(Why do we have hair in such random places? - Nina G. Jablonski)

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    shuting1215 發佈於 2022 年 01 月 04 日
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