Shovel-shaped incisors have long been hailed by proponents of the continuity hypothesis for East Asian hominins as the “most powerful evidence” — claiming an unbroken lineage from Yuanmou Man (1.75 million years ago) to modern East Asians, and further asserting that this trait is linked to the EDAR V370A variant, thereby “providing independent support for the continuity hypothesis at the molecular level.”This paper systematically evaluates the validity of this evidentiary chain from the perspectives of molecular chronology, population genetics, ancient DNA evidence, and reproducibility. Analysis shows: (1) EDAR V370A arose approximately 30,000 years ago in Central China, yet shovel-shaped incisors in East Asia date back 1.75 million years — a gene only 30,000 years old cannot explain a morphological trait that has existed for 1.75 million years, in blatant violation of the physical arrow of time; (2) Shovel-shaped incisors are not unique to East Asia — Neanderthals also possess this trait; (3) The EDAR gene encodes a protein (378 amino acids, molecular weight ~42 kDa) and ancient DNA has a half-life of approximately 521 years — there is an insurmountable barrier spanning hundreds of thousands of years, leaving fossil genotypes completely unknown; (4) The functional adaptation hypothesis (processing plant seeds and grinding plant matter) matches the origin and dispersal timeline of EDAR V370A perfectly in both time and geography, whereas the bloodline continuity hypothesis must remain silent before the temporal paradox; (5) Differences in shovel-shaped incisor frequency between modern and ancient populations within the same region cannot be explained by bloodline continuity — they can only be explained by adaptive selection. Overall assessment: The evidentiary chain linking shovel-shaped incisors to EDAR V370A is broken at three levels — temporal sequence, causation, and genotype availability — and therefore does not possess the scientific qualifications of a bloodline evolutionary marker.
Jing Zhang (Mon,) studied this question.