Nutritional Niche Construction and Local Adaptation: The Aquatic Resource-Driven Hypothesis of EDAR V370A in East Asia

The EDAR V370A allele is one of the strongest targets of positive selection in East Asian populations, yet the ecological driver of this selection remains unresolved. Here we propose a testable hypothesis: the stable availability of aquatic resources (including protein and key trace elements such as iodine and zinc) in the Late Pleistocene river‑lake and coastal ecosystems of northern China constituted the selective pressure driving EDAR V370A. We introduce the framework of “nutritional niche construction” and synthesize paleoenvironmental, archaeological, and stable isotopic evidence from Late Pleistocene northern China. We argue that the selective advantage of this allele was realized on an altered fitness landscape, where aquatic resources offset the metabolic costs of EDAR 370A’s pleiotropic effects (increased eccrine gland density, hair follicle thickness, and mammary branching). The hypothesis generates three empirically testable predictions regarding spatial correlation, temporal dynamics, and individual‑level isotopic signatures. We also discuss potential counterexamples (e.g., the Jōmon of Japan) to refine the scope of the hypothesis, proposing that EDAR V370A’s advantage lies in “alleviating deficiency” rather than “augmenting sufficiency.” This framework provides a novel theoretical perspective on local adaptation and phenotypic differentiation in East Asian populations.