Adaptation and co‐adaptation of skin pigmentation and vitamin D genes in native Americans

Abstract

We carried out an exhaustive review regarding human skin color variation and how much it may be related to vitamin D metabolism and other photosensitive molecules. We discuss evolutionary contexts that modulate this variability and hypotheses postulated to explain them; for example, a small amount of melanin in the skin facilitates vitamin D production, making it advantageous to have fair skin in an environment with little radiation incidence. In contrast, more melanin protects folate from degradation in an environment with a high incidence of radiation. Some Native American populations have a skin color at odds with what would be expected for the amount of radiation in the environment in which they live, a finding challenging the so‐called “vitamin D–folate hypothesis.” Since food is also a source of vitamin D, dietary habits should also be considered. Here we argue that a gene network approach provides tools to explain this phenomenon since it indicates potential alleles co‐evolving in a compensatory way. We identified alleles of the vitamin D metabolism and pigmentation pathways segregated together, but in different proportions, in agriculturalists and hunter‐gatherers. Finally, we highlight how an evolutionary approach can be useful to understand current topics of medical interest.

Uncovering Signals of Positive Selection in Peruvian Populations from Three Ecological Regions

“…As for the VDR gene, it was detected within a large candidate region in the top 10 signals of selection exclusively detected in highlands with the XP-EHH statistic when using the rainforest ecoregion as reference. Such a selection signal at VDR could result from a co-adaptation to reach optimal levels of vitamin D in an environment where strong UV radiation could have also favored darker skin pigmentation ( Missaggia et al . 2020 ).…”

Deconstructing Eurocentrism in skin pigmentation research via the incorporation of diverse populations and theoretical perspectives

“…As previously mentioned, much of the current research evaluating skin pigmentation variation in Indigenous people from the Americas has centered admixed Latinx populations. 9,53,54,74 75 presents data illustrating clearly distinctive profiles of tanning intensity between European Americans and Latinx Americans. 9,75 Extending this work by including ancient individuals from diverse ecological zones in the Americas will expand awareness around the genetic landscape contributing to tanning.…”

“…It is often thought that the relatively recent arrival of people in the Americas is what informs the disconnect between the predicted pigmentation phenotypes based on the vitamin D-folate hypothesis and present skin pigmentation variation within Indigenous people from the Americas. 1,9,54,74 Cultural practices like diet and sun barriers like clothing also heavily influence noted pigmentation phenotypes. 9,54,74 Therefore, of work including ancient individuals will also aid in understanding whether there might be connections between…”

Parallel evolution in human populations: A biocultural perspective

“…65,101 It could, therefore, be hypothesized that selection for lighter skin was tied to this cultural shift, with selective pressures increasing only after farming became the main subsistence strategy and diets shifted away from fish that were high in vitamin D, similar to what has been hypothesized for some Indigenous groups in the Americas. 102,103 Future biocultural studies should investigate this possibility further.…”