Colloquium paper: human skin pigmentation as an adaptation to UV radiation.
Level 5 - mechanism / opinion, no new human data
Narrative review and evolutionary theory synthesis without new empirical human data (by design analogy).
PubMed 20445093 · doi:10.1073/pnas.0914628107
What was done
Colloquium paper reviewing the evolutionary and physiological mechanisms that shaped human skin pigmentation clines in response to geographic variation in ultraviolet radiation.
What was found
The abstract reports no numerical data or effect sizes. It describes two selective clines: dark, eumelanin-rich skin evolved near the equator to protect folate and 5-methyltetrahydrofolate from photolysis and reactive oxygen species under high UVA and dual-peak UVB, while depigmented skin evolved at higher latitudes with low annual and summer peak UVB to sustain cutaneous vitamin D3 photosynthesis. Facultative tanning evolved in populations settling between approximately 23 and 46 degrees latitude with strong seasonal UVB variation, and depigmented skin evolved multiple times via independent genetic pathways.
Why it matters
Synthesizes the evolutionary framework explaining human skin pigmentation diversity as an adaptive balance between folate photoprotection and vitamin D3 synthesis.
Limits
The abstract describes a narrative theoretical synthesis containing no primary empirical human data, quantitative measurements, sample sizes, or statistical testing.
Cited by
- supports Melanin absorbs energy to protect skin DNA from sun damage, and genetic variants associated with red hair evolved in northern latitudes to allow people to synthesize vitamin D by reducing melanin-mediated UV blockage.