Light skin

Light skin is a human skin color that has a low level of eumelanin pigmentation as an adaptation to environments of low UV radiation.^[1][2][3] Light skin is most commonly found amongst the native populations of Europe, East Asia^[4][5][6], West Asia, Central Asia, and North Asia as measured through skin reflectance.^[7] People with light skin pigmentation are often referred to as "white"^[8][9] although these usages can be ambiguous in some countries where they are used to refer specifically to certain ethnic groups or populations.^[10]

Humans with light skin pigmentation have skin with low amounts of eumelanin, and possess fewer melanosomes than humans with dark skin pigmentation. Light skin provides better absorption qualities of ultraviolet radiation, which helps the body to synthesize higher amounts of vitamin D for bodily processes such as calcium development.^[3][11] On the other hand, light-skinned people who live near the equator, where there is abundant sunlight, are at an increased risk of folate depletion. As a consequence of folate depletion, they are at a higher risk of DNA damage, birth defects, and numerous types of cancers, especially skin cancer.^[12] Humans with darker skin who live further from the tropics may have lower vitamin D levels, which can also lead to health complications, both physical and mental, including a greater risk of developing schizophrenia.^[13] These two observations form the "vitamin D–folate hypothesis", which attempts to explain why populations that migrated away from the tropics into areas of low UV radiation^[14] evolved to have light skin pigmentation.^[3][15][16]

The distribution of light-skinned populations is highly correlated with the low ultraviolet radiation levels of the regions inhabited by them. Historically, light-skinned populations almost exclusively lived far from the equator, in high latitude areas with low sunlight intensity.^[17] Due to colonization, imperialism, and increased mobility of people between geographical regions in recent centuries, light-skinned populations today are found all over the world.^[3][18]