Divided zygoma in Holocene human populations from Northern China

Abstract

ObjectivesDivided zygoma (DZ) occurs in contemporaneous human populations, with the highest incidences in people from East Asia and Southern Africa. The present study examines the prevalence and variation of this condition in the Holocene populations of Northern China for the first time.MethodsIn this study, 1145 skulls from various human populations living in Northern China from the Neolithic Age to recent dynasties (5000‐300 years BP) were examined. Specifically, cranial measurements and a CT scan were conducted to quantify craniofacial morphology.ResultsFifteen skulls were identified with DZ, revealing an overall prevalence of 1.3% in the collection, while it was determined to be higher in North Asian and Northeast Asian regional groups. In skulls with unilateral DZ, the superior division of the zygoma was generally slender, while the inferior division of the zygoma was more robust. In skulls with bilateral DZ, the maxillae were generally more laterally extended. Moreover, unilateral DZ skulls displayed differences in cortical bone thickness between two sides of the facial skeleton.DiscussionIn context, the distribution pattern within these data points toward a greater prevalence of the DZ phenotype in North and Northeast Asian regional groups, suggesting a hypothesis that the DZ trait is more frequent in populations characterized by flat and broad faces. Accordingly, further studies into the DZ condition will deepen our understanding of developments in plasticity, variation, and recent evolution of the human cranium.

The divided zygoma: a meta-analysis of its prevalence with a review of the literature

“…Similarly, Anil et al did not observe any differences in gender and side preferences in the cadaveric and radiograph groups [1]. Zhang also reported that the existence of bipartite or tripartite zygomatic bones was not related to gender, age, or side [38].…”

“…In addition, other geographic regions, except Asian populations, have small elucidated data by the authors up to the present times. Some researchers collected their data from the skulls from the old days, such as: Kozintsev, who used skulls from the bronze age to find the posterior trace of the OJ, or Anil, who found DZ among Anatolian skulls from the 18th century, and Wang and Zhang, who described many DZs in museums collections and archeological sites [1, 33,38]. The majority of the studies investigating the DZ focused purely on the prevalence of this structure, rather than its morphometric properties [33].…”

“…Although some authors pointed out that the frequency of DZ in the Japanese population is too low to consider this character as a Japanese trait [22], many authors still use this synonym. Typically, the zygoma is a single midfacial bone and plays a significant role in the support and integration of the craniofacial skeleton, and the masticatory apparatus by its attachment to the masseter muscle [38]. It also contributes to the formation of the lateral wall and floor of the orbit, parts of the temporal and infratemporal fossa [36].…”

Anatomical variations of the zygomaticofacial foramen and its related canal through the zygomatico-orbital and zygomaticotemporal foramina in dry human skulls

“…The zygomatic bone can occasionally be divided in half by a vertical or a horizontal suture. Due to its frequent observation in Japanese populations, this of bipartite bone has been given the name os Japonicum (os Ainoicum) [29][30][31]. Where the zygomatic bone and temporal bone converge to form the zygomatic arch, a sutural bone may be visible.…”

Anatomical variations of the zygomaticofacial foramen and its related canal through the zygomatico-orbital and zygomaticotemporal foramina in dry human skulls

“…The zygomatic bone can occasionally be divided in half by a vertical or a horizontal suture. Due to its frequent observation in Japanese populations, this type of bipartite bone has been given the name os Japonicum (os Ainoicum) [29][30][31]. Where the zygomatic bone and temporal bone converge to form the zygomatic arch, a sutural bone may be visible.…”