Assessing intrasample variation: analysis of Rapa Nui (Easter Island) museum cranial collections example

Area of Science:

• Osteology
• Physical Anthropology
• Bioarchaeology

Background:

• Previous osteological studies often pooled Polynesian cranial samples, potentially obscuring intrasample variation.
• Few studies have assessed variation within pooled skeletal data from different islands or museum collections representing the same population.

Purpose of the Study:

• To examine Easter Island (Rapa Nui) crania from various museums to determine if significant differences exist among these collections.
• To evaluate the reliability of pooled skeletal data for representing a specific population.

Main Methods:

• Utilized the NORM statistical program for multiple imputation of incomplete multivariate datasets.
• Applied a variance comparison method using variance/covariance matrices to compare six Rapa Nui museum samples against a baseline reference sample.
• Assessed intrasample variability in male and female Rapa Nui skeletal material.

Main Results:

• The six Rapa Nui museum samples exhibited minimal intrasample variability when compared to the baseline reference sample (MAPSE).
• This consistency was observed despite samples being collected at different times and by different individuals.
• The study confirmed the efficacy of multiple imputation and variance comparison in handling missing data and identifying sample variation.

Conclusions:

• Pooled skeletal data from different Rapa Nui museum collections can reliably represent the population.
• Statistical methodologies like multiple imputation and variance comparison are effective for analyzing and validating pooled osteological data.
• The findings support the use of such methods in future studies of prehistoric populations.