Craniofacial evolution in Polynesia: a geometric morphometric study of population diversity

"Feeling at home in Vanuatu": Integration of newcomers from the East during the last millennium

Several localities across the Vanuatu archipelago (Melanesia), so-called 'Polynesian Outliers', are inhabited by communities that display Polynesian linguistic and cultural features although being located outside the Polynesian Triangle. Several introductions of Polynesian genetic components to Central and Southern Vanuatu during the last millenium have resulted in the cultural distinctiveness observed among the Polynesian Outliers in Vanuatu. However, social, political or economic process surrounding the exchange of genes between Polynesian and local individuals remain unidentified. Recent bioanthropological studies suggest the existence of female mobilities from neighboring regions to Vanuatu but also to the Polynesian Outliers of Taumako (Solomon Islands) within patrilocal societies. We aim to examine the hypothesis that Polynesian biological affinities observed in ancient individuals from Vanuatu are gendered or sex-specific, and that some of the Polynesian migrations during the last millennium may have involved practices of exogamy. By reconstructing phenotypes and biological identities from 13 archaeologically-recovered human skulls (400-300 years ago) from "Polynesian-related" regions of Vanuatu, we provide new insights to better contextualize the settlement patterns of Polynesian individuals. Eastern-Pacific associated phenotype are observable in 4 women from the Eretok burial complex (Efate region) and the Polynesian Outlier of Futuna, who were buried in close proximity to individuals with Western-Pacific associated phenotype. We suggest that close integration of individuals from the East into the local Vanuatu society, as well as the practice of exogamy, might have been key processes contributing to the preservation of Polynesian cultural features in Vanuatu over the past millennium. Our finding are cross-referenced with oral records from these two areas, as well as the known genetic makeup of the Vanuatu Polynesian Outliers.

Body size and allometric variation in facial shape in children

OBJECTIVES

Morphological integration, or the tendency for covariation, is commonly seen in complex traits such as the human face. The effects of growth on shape, or allometry, represent a ubiquitous but poorly understood axis of integration. We address the question of to what extent age and measures of size converge on a single pattern of allometry for human facial shape.

METHODS

Our study is based on two large cross-sectional cohorts of children, one from Tanzania and the other from the United States (N = 7,173). We employ 3D facial imaging and geometric morphometrics to relate facial shape to age and anthropometric measures.

RESULTS

The two populations differ significantly in facial shape, but the magnitude of this difference is small relative to the variation within each group. Allometric variation for facial shape is similar in both populations, representing a small but significant proportion of total variation in facial shape. Different measures of size are associated with overlapping but statistically distinct aspects of shape variation. Only half of the size-related variation in facial shape can be explained by the first principal component of four size measures and age while the remainder associates distinctly with individual measures.

CONCLUSIONS

Allometric variation in the human face is complex and should not be regarded as a singular effect. This finding has important implications for how size is treated in studies of human facial shape and for the developmental basis for allometric variation more generally.

How much impact do gains in height have on shoulder breadths within Taiwanese families?

OBJECTIVES

This study investigates allometric changes in shoulder breadths relative to changes in stature arising from rapidly changing developmental circumstances within 107 Taiwanese families. It speaks to broader issues related to the extent of phenotypic plasticity of body breadths humans are capable of in response to reductions in developmental stressors.

METHODS

An examination of relationships between shoulder breadth and height within individuals in each generation was followed by evaluation of patterns of difference between same-sex parent-offspring pairs in height and shoulder breadth.

RESULTS

Height was similarly positively correlated with shoulder breadth within fathers, mothers, sons, and daughters (P ≤ 0.002). Variance accounted for ranged from an adjusted R² of 0.201 among fathers to 0.151 for sons, with mothers' and daughters' values being 0.187 and 0.181, respectively. Comparisons of differences within families indicate that parents who were shorter than their same-sex offspring also tended to have modestly narrower biacromial breadths (father-son pairs: adjusted R²  = 0.112; t = 2.82, P = .007; mother-daughter pairs: adjusted R²  = 0.135; t = 2.97, P = 0.005).

CONCLUSIONS

Taken as a whole, results here support the view that secular changes in stature are not accompanied by similar changes in body breadths, perhaps so that responses to developmental environmental improvements do not alter thermoregulatory equilibria that reflect long-term evolutionary processes. These results indirectly constrain plausible hypotheses about how ancestors of Austronesian speakers altered their body size and shape as they voyaged to Fiji, Western Polynesia, and beyond.

Early Lapita skeletons from Vanuatu show Polynesian craniofacial shape: Implications for Remote Oceanic settlement and Lapita origins

With a cultural and linguistic origin in Island Southeast Asia the Lapita expansion is thought to have led ultimately to the Polynesian settlement of the east Polynesian region after a time of mixing/integration in north Melanesia and a nearly 2,000-y pause in West Polynesia. One of the major achievements of recent Lapita research in Vanuatu has been the discovery of the oldest cemetery found so far in the Pacific at Teouma on the south coast of Efate Island, opening up new prospects for the biological definition of the early settlers of the archipelago and of Remote Oceania in general. Using craniometric evidence from the skeletons in conjunction with archaeological data, we discuss here four debated issues: the Lapita-Asian connection, the degree of admixture, the Lapita-Polynesian connection, and the question of secondary population movement into Remote Oceania.