肤色的科学 The science of skin color

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

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

So what's to account for that difference and how did our skin come to take on so many different hues to begin with?

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

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

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

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.

But humans weren't always like this.

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

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

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