The story of our hair, our hair story, if you will, is pretty tangled（纠缠的）. Scientists are still straightening（整顿） out the facts, combing through questions, cutting to the root（根） of this biological（生物的） tale（故事）. We must ash（灰）. What's the deal with hair? Don't worry, I know you're about to die. We're cutting the puns, starting now.

  Hair is a big part of our culture. It's hit Broadway（百老汇大街(的)）, whipped（鞭笞） back and forth（向前）, even spawned（产卵） its own musical genre（类型）. And made this possible. Impressive, Kyle. But W, the actual（实际的） F, is it? Hair is made of keratin, the same protein（蛋白质） that forms your fingernails, with a few extra ingredients.

  It gets its color from two types of melanin, brown-black U melanin and red-yellow pheomelanin. These pigments（[生]色素） are produced down in the hair follicle. Whether each strand（使搁浅） comes out curly or straight, depends on the angle（角度） of the follicle itself. Your DNA combination（结合） dictates（口述） whether you turn out to be a thorg, a Loki, or maybe a Weasley. Blonds（白肤碧眼金发的人） might have more fun, but they don't have a lot of pigment. They have a mix of the two hues（色调）, but at low levels.

  U melanin dominates（控制） brunette heads, but red heads have mostly reddish（微红的） pheomelanin. This pigment ratio（比率） is controlled by a gene（[遗] 基因）, which also controls the melanin in our skin. In Africa, that pigment gene doesn't really vary（改变）. It would make sense. You need a lot of U melanin to absorb（吸收） UV rays（射线）, but the farther we journey from our tropical（热带的） origins（起源）, the more variation（变化） we see.