* Melanin and Sunlight: Melanin is a pigment in the skin that protects against UV radiation. People in regions with high sun exposure (like Africa) evolved to have more melanin, resulting in darker skin, to protect against skin damage and folate depletion.
* Vitamin D Synthesis: Vitamin D is essential for bone health and immune function. The body produces vitamin D when skin is exposed to sunlight. In regions with less sunlight (like Northern Europe and Asia), darker skin would hinder vitamin D production, leading to deficiencies.
* Evolutionary Advantage: As humans migrated to higher latitudes with less sunlight, those with lighter skin (less melanin) were able to produce more vitamin D. This provided a survival advantage, as they had healthier bones and stronger immune systems. Over time, this led to a greater prevalence of lighter skin in these populations.
Therefore, lighter skin is an adaptation to environments with lower sunlight levels, allowing for sufficient vitamin D synthesis.