Human skin color evolved in response to sunlight.

In regions near the equator, darker skin protects against intense ultraviolet radiation. But farther north, where sunlight is weaker, that protection becomes a disadvantage.

To produce vitamin D, the body needs ultraviolet light. In low-sun environments, heavily pigmented skin can block too much of it. Over many generations, lighter skin evolved because it allowed more sunlight to penetrate, improving vitamin D production.

This mattered for survival. Vitamin D plays a key role in bone development and immune function, and deficiencies can lead to serious health problems. In northern climates, individuals with lighter skin had an advantage, especially during long winters with limited sunlight.