Document Type
Article
Publication Date
5-8-2018
Keywords
mammary epithelium, dental anthropology, Beringia, adaptation, UV radiation
Abstract
Because of the ubiquitous adaptability of our material culture, some human populations have occupied extreme environments that intensified selection on existing genomic variation. By 32,000 years ago, people were living in Arctic Beringia, and during the Last Glacial Maximum (LGM; 28,000–18,000 y ago), they likely persisted in the Beringian refugium. Such high latitudes provide only very low levels of UV radiation, and can thereby lead to dangerously low levels of biosynthesized vitamin D. The physiological effects of vitamin D deficiency range from reduced dietary absorption of calcium to a compromised immune system and modified adipose tissue function. The ectodysplasin A receptor (EDAR) gene has a range of pleiotropic effects, including sweat gland density, incisor shoveling, and mammary gland ductal branching. The frequency of the human-specific EDAR V370A allele appears to be uniquely elevated in North and East Asian and New World populations due to a bout of positive selection likely to have occurred circa 20,000 y ago. The dental pleiotropic effects of this allele suggest an even higher occurrence among indigenous people in the Western Hemisphere before European colonization. We hypothesize that selection on EDAR V370A occurred in the Beringian refugium because it increases mammary ductal branching, and thereby may amplify the transfer of critical nutrients in vitamin D-deficient conditions to infants via mothers’ milk. This hypothesized selective context for EDAR V370A was likely intertwined with selection on the fatty acid desaturase (FADS) gene cluster because it is known to modulate lipid profiles transmitted to milk from a vitamin D-rich diet high in omega-3 fatty acids.
Publication Title
Proceedings of the National Academy of Sciences of the United States of America
Volume
115
Issue
19
First Page
E4426
Last Page
E4432
DOI
10.1073/pnas.1711788115
Required Publisher's Statement
Copyright © 2018 the Author(s). Published by PNAS.
Recommended Citation
Hlusko LJ, Carlson J, Chaplin G, Elias SA, Hoffecker JF, Huffman M, Jablonski NG, Monson TA, O’Rourke DH, Pilloud MA, Scott GR. 2018. Environmental selection during the last ice age on the mother-to-infant transmission of vitamin D and fatty acids through breast milk. Proceedings of the National Academy of Sciences. www.pnas.org/cgi/doi/10.1073/pnas.1711788115
Subjects - Topical (LCSH)
Mammary glands; Dental anthropology; Ultraviolet radiation; Vitamin D
Geographic Coverage
Bering Land Bridge
Genre/Form
articles
Type
Text
Rights
Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this document for commercial purposes, or for financial gain, shall not be allowed without the author’s written permission.
Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial-No Derivative Works 4.0 International License.
Language
English
Format
application/pdf
Comments
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1711788115/-/DCSupplemental.