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  • When ultraviolet sunlight hits our skin, it affects each of us a little differently.

    陽光的紫外線照射到我們的皮膚時,它對每個人的影響有點不同。

  • Depending on skin color, it'll take only minutes of exposure to turn one person beetroot-pink, while another requires hours to experience the slightest change.

    根據膚色的不同, 有些人曝曬幾分鐘後,皮膚就變得像甜菜根一樣紅,但有些人經過數小時卻只有輕微的變化。

  • So what's to account for that difference?

    那麼,是什麼造成這種差異呢?

  • And how did our skin come to take on so many different hues to begin with?

    而我們的皮膚又為什麼有這麼多不同的色調呢?

  • Whatever the color, our skin tells an epic tale of human intrepidness and adaptability, revealing its variance to be a function of biology.

    不論膚色,我們的皮膚述說了關於人類的無畏與適應性的史詩故事,顯示其多樣性是生物的一個功能。

  • It all centers around melanin, the pigment that gives skin and hair its color.

    其核心是「黑色素」,賦予皮膚與頭髮顏色的色素。

  • This ingredient comes from skin cells called melanocytes and takes two basic forms.

    此要素來自名為黑素細胞的皮膚細胞,有兩種基本型態。

  • There's eumelanin, which gives rise to a range of brown skin tones, as well as black, brown, and blond hair, and pheomelanin, which causes the reddish-browns of freckles and red hair.

    其一是「真黑素」,它會導致各種棕色調皮膚及黑色、棕色和金色的頭髮,另外就是「褐黑素」,它會導致紅棕色的雀斑和紅髮。

  • But humans weren't always like this.

    但人類並非一直是這樣的。

  • Our varying skin tones were formed by an evolutionary process driven by the Sun.

    我們不同的皮膚色調是受太陽的影響,經演化而形成。

  • It began some 50,000 years ago when our ancestors migrated north from Africa and into Europe and Asia.

    始於 5 萬多年以前,當時我們的祖先從非洲往北遷移到歐洲和亞洲。

  • These ancient humans lived between the Equator and the Tropic of Capricorn, a region saturated by the Sun's UV-carrying rays.

    這些古代人類住在赤道與南迴歸線之間,這是太陽的紫外線達飽和的地區。

  • When skin is exposed to UV for long periods of time, the UV light damages the DNA within our cells, and skin starts to burn.

    當皮膚長期暴露於紫外線下,紫外線會損害我們的細胞內的 DNA,而皮膚就會開始灼傷。

  • If that damage is severe enough, the cells' mutations can lead to melanoma, a deadly cancer that forms in the skin's melanocytes.

    如果皮膚損傷夠重,細胞突變會導致「黑素瘤」,它是由皮膚的黑素細胞形成的一種致命癌症。

  • Sunscreen as we know it today didn't exist 50,000 years ago.

    現今眾所周知的防曬產品在 5 萬年前並不存在。

  • So how did our ancestors cope with this onslaught of UV?

    那麼我們祖先怎麼應付紫外線的攻擊呢?

  • The key to survival lay in their own personal sunscreen manufactured beneath the skinmelanin.

    生存關鍵在於他們的皮膚下製造的防曬──黑色素。

  • The type and amount of melanin in your skin determines whether you'll be more or less protected from the sun.

    你皮膚裡黑色素的種類和數量決定了你的防曬能力。

  • This comes down to the skin's response as sunlight strikes it.

    簡單來說就是太陽照射時皮膚的反應。

  • When it's exposed to UV light, that triggers special light-sensitive receptors called rhodopsin, which stimulate the production of melanin to shield cells from damage.

    皮膚暴露於紫外線下時會觸發特殊的感光受體「視紫質」,它會刺激黑色素的產生, 以避免皮膚受到傷害。

  • For light-skin people, that extra melanin darkens their skin and produces a tan.

    多餘的黑色素會使淺膚色的人膚色變深,變成棕褐色。

  • Over the course of generations, humans living at the Sun-saturated latitudes in Africa adapted to have a higher melanin production threshold and more eumelanin, giving skin a darker tone.

    在世代繁衍的過程中,生活在陽光充足的非洲緯度地區的人類為適應環境,能生產較多的黑色素及較多真黑素,使其膚色較深。

  • This built-in sun shield helped protect them from melanoma, likely making them evolutionarily fitter and capable of passing this useful trait on to new generations.

    這與生俱來的遮陽罩使他們不易罹患黑色素瘤,使他們演化以更適應居住環境,並將這個有用的特質傳給後代子孫。

  • But soon, some of our Sun-adapted ancestors migrated northward out of the tropical zone, spreading far and wide across the Earth.

    但很快的,一些適應太陽的祖先向北遷移,離開了熱帶區,遍佈地球各個角落。

  • The further north they traveled, the less direct sunshine they saw.

    他們越往北移動, 直射的陽光就越少。

  • This was a problem because although UV light can damage skin, it also has an important parallel benefit.

    這是一個問題, 因為雖然紫外線會損傷皮膚,但它也帶來同等重要的好處。

  • UV helps our bodies produce vitamin D, an ingredient that strengthens bones and lets us absorb vital minerals, like calcium, iron, magnesium, phosphate, and zinc.

    紫外線可使我們身體產生維生素D,這種成分可以強化骨骼,並幫助我們吸收重要礦物質的成分,如鈣、鐵、鎂、磷酸鹽和鋅。

  • Without it, humans experience serious fatigue and weakened bones that can cause a condition known as rickets.

    少了它,人類會感到極度疲勞,並造成骨骼脆弱,導致「佝僂病(軟骨病)」。

  • For humans whose dark skin effectively blocked whatever sunlight there was, vitamin D deficiency would have posed a serious threat in the north.

    對那些能有效阻擋所有陽光的皮膚黝黑者而言,到了北方,缺乏維生素 D 會造成嚴重的健康威脅。

  • But some of them happened to produce less melanin.

    但他們之中有些人,恰好擁有較少的黑色素。

  • They were exposed to small enough amounts of light that melanoma was less likely, and their lighter skin better absorbed the UV light.

    他們暴露較少的陽光下,所以罹患黑色素瘤的可能性較小,而他們較淺的皮膚更容易吸收紫外線。

  • So they benefited from vitamin D, developed strong bones, and survived well enough to produce healthy offspring.

    於是他們受益於維生素 D,擁有強健骨骼,存活了下來, 以繁育健康的後代。

  • Over many generations of selection, skin color in those regions gradually lightened.

    經過數代的物竸天擇,那些地區的人膚色逐漸變淡。

  • As a result of our ancestors' adaptability, today the planet is full of people with a vast palette of skin colors, typically, darker eumelanin-rich skin in the hot, sunny band around the Equator, and increasingly lighter pheomelanin-rich skin shades fanning outwards as the sunshine dwindles.

    由於我們祖先的適應能力,今天地球充滿了各種不同膚色的人,通常富含真黑素的深膚色者居住在炎熱、陽光充足的赤道附近,而隨著陽光的減少,富含褐黑素且膚色漸淺者則由此區呈扇型向外擴散。

  • Therefore, skin color is little more than an adaptive trait for living on a rock that orbits the Sun.

    因此,膚色可不只是為了生活在繞太陽運行的岩石上的適應特性。

  • It may absorb light, but it certainly does not reflect character.

    它可以吸收陽光,但它肯定不代表個性。

When ultraviolet sunlight hits our skin, it affects each of us a little differently.

陽光的紫外線照射到我們的皮膚時,它對每個人的影響有點不同。

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B2 中高級 中文 TED-Ed 皮膚 黑色素 紫外線 膚色 陽光

【TED-Ed】為什麼不同地區的人會有不同膚色?膚色演化的科學 (【TED-Ed】The science of skin color - Angela Koine Flynn)

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    Sh, Gang (Aaron) 發佈於 2021 年 08 月 29 日
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