A Morphofunctional Hypothesis for Selection on EDAR V370A and Associated Elements of Sinodonty

Abstract

The phenomenon of sinodonty refers to a suite of dental characters shared between East Asian and Native American populations, and most prominently to the presence of shoveled incisors.  Although this syndrome is a conspicuous aspect of dental differentiation among extant human populations, elements of which have been recent subject of detailed genetic analysis, adaptive consequences of shoveled incisors and related features remains unclear.  Here, I hypothesize that many of the associated differences in dentition (along with reduction in mandibular length and increases in salivary gland branching) arose in parallel with the opportunistic consumption of wild rice and millet in central and northern China, respectively, and with their subsequent domestication in the Upper Paleolithic.  More efficient mastication and digestion of plant grains (and of other starchy foods obtained via broad-spectrum foraging) would potentially have been enabled by these traits, yielding greater rates of nutritional intake as wild crops were progressively domesticated.  This functional hypothesis, although not mutually exclusive relative to other proposed selective factors, matches the estimated timeline in China for both origin and time to fixation of the associated allele (EDAR V370A), and is consistent with chronic energetic gain and fitness benefits independent of any assumptions for concurrent climatic conditions.