Darker skin is more prevalent in high-uv areas. dr. nina jablonski proposed a hypothesis to explain the selective pressure for darker skin in these environments. on what evidence did she base this hypothesis? darker skin is more prevalent in high-uv areas. dr. nina jablonski proposed a hypothesis to explain the selective pressure for darker skin in these environments. on what evidence did she base this hypothesis? the melanin in darkly pigmented skin protects circulating folate from being destroyed by uv radiation, and folate is important in human reproduction the melanin in darkly pigmented skin protects dna from uv radiation, and uv radiation can cause skin cancer people of african descent all have the same version of the mc1r gene, indicating that this gene was under selection she discovered that people of african descent have less folate circulating in their blood and that folate is important for human reproduction