Does the distribution of Wormian bone frequencies across different world regions reflect genetic affinity between populations?

Abstract

Wormian, or sutural bones, are additional, irregularly shaped bone fragments that can occur within cranial sutures. These bones may arise due to various factors, including mechanical pressure on skull bones during early ontogenetic stages, such as during artificial cranial deformations, or due to genetic and environmental influences. This study investigates the potential genetic basis of sutural bones by comparing their frequencies across diverse global regions. It analyzed 33 craniological series, encompassing 2059 crania, to assess the frequency of sutural bones in the coronal, squamous, lambdoid, and occipitomastoid sutures among skeletal populations from regions including Aboriginal Australia, Melanesia, Southeast Asia, Siberia, Europe, and Native America. Biological distances between populations were calculated using Smith’s mean measure of divergence (MMD), with results visualized through multidimensional scaling. The analysis identified distinct clusters of Caucasian and Siberian populations. Siberian aboriginal populations are compactly grouped, consistent with mtDNA data indicating genetic roots dating back to the Neolithic inhabitants of the Lake Baikal region. Further, differentiation within these populations is linked to the founder effect and gene flow. Notably, genetically related groups like the Inuit and Chukchi of Chukotka differ from other Siberian groups. In contrast, southern Siberian populations, such as the Buryats and Mongols, are closely positioned, aligning with genetic data. The differentiation between Southeast Asian and African regions was subtler, with their clusters largely overlapping. Yet, genetic links between populations were observed in some cases. Thus, Australians, Melanesians, and Papua New Guineans were located close to each other on the multidimensional scaling map, as were two African populations. The findings tentatively suggest a potential genetic component in the expression of Wormian bones, although this hypothesis requires further empirical support, particularly through genetic studies. While genetic factors may influence the expression of Wormian bones, environmental conditions and pathological processes also play significant roles. It can be suggested that Wormian bones could potentially serve as an additional tool in kinship analysis within burials; however, their utility significantly depends on the extent of their genetic influence. If future genetic studies confirm a substantial genetic component and its dominance over environmental factors, the use of these bones in anthropological and forensic analyses would receive additional validation.