Variation and the evolutionary drivers of diversity in the genus Paranthropus

Craniodental robusticity in Paranthropus has led many researchers to posit that all the species in this genus share a common adaptation to a diet of hard foods. Recent research on craniodental morphology, microwear, biomechanics, and isotopes, by contrast, has suggested that substantial variation exists within the genus Paranthropus, both in terms of ecological niches occupied by the three recognized species within the genus and the amount of consumed hard and compliant foods. Rather than pointing to a common adaptive suite, these studies suggest that the species were adaptively distinct from each other. However, current approaches to understanding craniodental morphology do not present a clear picture of how these speciesspecific adaptations differ. It is also not clear whether all aspects of morphology that have been attributed to adaptation are indeed adaptive, rather than the products of non-adaptive processes. This study examines variation across the three known Paranthropus taxa (P. aethiopicus, P. boisei and P. robustus; N=39) using an approach that tests for adaptive morphology against a null hypothesis of random change (i.e. drift). Extant species (Homo sapiens (N=150), Gorilla gorilla (N=150), Pan troglodytes (N=143) act as analogues for Paranthropus variance/covariance (V/CV). Results reveal a high magnitude of variation within and between species across mandibular and cranial regions, especially when including the P. robustus individuals DNH 7 & 8 from Drimolen. Drift cannot be rejected for the bulk of comparisons. Neutrality tests detect adaptive divergence between P. robustus and the other two species, but not between P. aethiopicus and P. boisei. Reconstructed selection vectors indicate that both positive and negative directional selection have driven diversification in mandibular and tooth dimensions and in the cranium, resulting in variable morphological responses including considerable evidence for correlated selection

The role of selection in shaping the cranio-mandibular morphology of Paranthropus

This dataset contains 95th percentile values from frequency distributions of Mahalanobis’ distances (D2) calculated from extant hominoid models for each analysis used in the study. These values are used to evaluate the significance of the D2 values between fossil specimens. If D2 values are greater than the values presented in this table, then it is classified as statistically significant. Bolded red values indicate distances that are statistically significant compared to all of the 95% values from frequency distributions of Mahalanobis' distances calculated between extant hominoid models. Non-bolded red values indicate distances that are significant for at least one model.</div

Enamel proteins reveal biological sex and genetic variability within southern African Paranthropus

The evolutionary relationships among extinct African hominin taxa are highly debated and largely unresolved, due in part to a lack of molecular data. Even within taxa, it is not always clear, based on morphology alone, whether ranges of variation are due to sexual dimorphism versus potentially undescribed taxonomic diversity. For Paranthropus robustus , a Pleistocene hominin found only in South Africa, both phylogenetic relationships to other taxa 1,2 and the nature of intraspecific variation 3–6 are still disputed. Here we report the mass spectrometric (MS) sequencing of enamel proteomes from four ca. 2 million year (Ma) old dental specimens attributed morphologically to P. robustus, from the site of Swartkrans. The identification of AMELY-specific peptides and semi-quantitative MS data analysis enabled us to determine the biological sex of all the specimens. Our combined molecular and morphometric data also provide compelling evidence of a significant degree of variation within southern African Paranthropus , as previously suggested based on morphology alone 6 . Finally, the molecular data also confirm the taxonomic placement of Paranthropus within the hominin clade. This study demonstrates the feasibility of recovering informative Early Pleistocene hominin enamel proteins from Africa. Crucially, it also shows how the analysis of these proteins can contribute to understanding whether hominin morphological variation is due to sexual dimorphism or to taxonomic differences. We anticipate that this approach can be widely applied to geologically-comparable sites within South Africa, and possibly more broadly across the continent