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Rocker jaw: Global context for a Polynesian characteristic.

George Richard Scott1, Kyra E Stull1, Andrea N Sbei2

  • 1Department of Anthropology, University of Nevada Reno, Reno, Nevada, USA.

Anatomical Record (Hoboken, N.J. : 2007)
|November 7, 2020
PubMed
Summary

The "rocker jaw" variant, a mandible lacking an antegonial notch, is most common in Polynesians but found globally. Its distribution offers insights into human population genetics and migration patterns.

Keywords:
Polynesiaglobal variationmandibular variantrocker jaw

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Area of Science:

  • Anthropology
  • Human Paleontology
  • Population Genetics

Background:

  • The "rocker jaw" is a mandible variant characterized by the absence of the antegonial notch.
  • This trait can lead to mandibular instability on flat surfaces.
  • Its global distribution in human populations is not well-documented.

Purpose of the Study:

  • To describe the global distribution of the "rocker jaw" variant across diverse human populations.
  • To investigate regional frequencies and population-specific variations of this trait.
  • To explore potential correlations between rocker jaw morphology and population genetics, craniofacial features, and migration hypotheses.

Main Methods:

  • Analysis of mandible morphology, specifically the presence or absence of the antegonial notch, in 12,733 individuals.
  • Data collection spanned populations across Asia, Europe, the Pacific, the Americas, North Africa, and Sub-Saharan Africa.
  • Frequencies were calculated for various geographic regions, with a focus on Polynesian and Oceanian subdivisions.

Main Results:

  • The "rocker jaw" trait is most frequent in Polynesians but present in all studied geographic regions.
  • Significant regional variations were observed, including distinctions within East Asian (Jomon, Ainu, Japanese), Arctic/Subarctic (Aleut, Northwest Coast, Inuit), and African populations.
  • The rarity of the trait in indigenous South Americans supports hypotheses of Polynesian voyagers reaching the continent.

Conclusions:

  • The global distribution of the "rocker jaw" variant provides insights into human population history and genetic relationships.
  • The trait's high frequency in Polynesians is linked to their unique craniofacial morphology, particularly basicranium structure and facial height, and potentially influenced by founder effect and genetic drift.
  • Observed regional patterns in rocker jaw distribution may reflect underlying genetic and dental distinctions between populations.