Sex-biased sampling may influence Homo naledi tooth size variation

Area of Science:

• Paleoanthropology
• Primate Paleontology
• Human Evolution

Background:

• Taxonomic debates in paleoanthropology often arise from high variation within hominin fossil assemblages, suggesting multiple species.
• The Homo naledi fossil assemblage from the Rising Star cave system displays remarkably low skeletal variation, prompting investigation into its causes.

Purpose of the Study:

• To investigate whether sex-biased sampling could explain the low phenotypic variation observed in the Homo naledi dental sample.
• To compare the variation in Homo naledi teeth to extant hominoid dental samples.

Main Methods:

• Calculated coefficients of variation for Homo naledi teeth.
• Compared these coefficients to those of eight extant hominoid samples.
• Employed a resampling procedure to simulate various sex ratios within the fossil sample size.

Main Results:

• Variation at four specific Homo naledi tooth positions (I₂, M₁, P⁴, M₁) was found to be exceptionally low.
• This low variation suggests the possibility that one sex may be poorly represented or absent in the dental sample.

Conclusions:

• Sex-biased sampling is a plausible explanation for the low phenotypic variation in certain aspects of the Homo naledi assemblage.
• Further research, including ancient DNA or enamel proteome analysis, is recommended for corroboration.
• Highlights the importance of considering taphonomic factors and sampling biases in fossil assemblages.