Editing Human skin color (section)

=== Functional considerations ===
Elias et. al. in 2010 showed a superior barrier function in darkly pigmented skin. Most protective functions of the skin, including the permeability barrier and the antimicrobial barrier, reside in the [[stratum corneum]] and the researchers surmise that the stratum corneum has undergone the most genetic change since the loss of human body hair. [[Natural selection]] would have favored mutations that protect this essential barrier; one such protective adaptation is the pigmentation of [[Hair follicle|interfollicular]] [[Epidermis (skin)|epidermis]], because it improves barrier function as compared to non-pigmented skin.<ref name="Elias2010"/>

The authors argue that lack of significant differences between modern light-skinned and dark-skinned populations in vitamin D deficiency, early death from UV-induced cancers and birth defects — as well as instances of light and dark populations living side-by-side in areas with similar UV — suggest the standard model is insufficient to explain the strong selection drive for pigmented skin.<ref name="Elias2010">{{cite journal |last1=Elias |first1=PM |last2=Menon |first2=G |last3=Wetzel |first3=BK |last4=Williams |first4=J |journal=American Journal of Human Biology |pmid=20209486 |year=2010 |volume=22 |issue=4 |pages=526–537 |title=Barrier Requirements as the Evolutionary "Driver" of Epidermal Pigmentation in Humans |doi=10.1002/ajhb.21043 |pmc=3071612}}</ref> Jablonski rejects this theory on the grounds that the human [[Sun tanning|tanning response]] is driven by UV-B exposure, not xeric stress, and that the positive selection for vitamin D production is "well-established".<ref name="Jablonski2017" />