Browsing by Author "Warren, Kerryn Ashleigh"

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    Of mice and hominins: using the craniomandibular morphology of hybrid mice to better understand hybrid morphologies in the Hominin fossil record
    (2017) Warren, Kerryn Ashleigh; Ackermann, Rebecca Rogers
    Since the sequencing of the Neanderthal genome in 2010, there has been an explosion of molecular research into hybridization and gene flow among hominin taxa in the Late Pleistocene. However, little research has focussed on how hybridization affects skeletal morphology. In regions and time periods where the recovery of ancient DNA is not possible, a thorough understanding of hybrid morphologies is essential for truly understanding hominin interactions in the past. This thesis examines the cranio-mandibular morphologies of hybrid mice across different degrees of phylogenetic relatedness (three sub-specific hybrids and one specific hybrid) and through several generations (F1s, B1s and F2s for the sub-specific hybrids), in order to build an animal model for better understanding hybrid morphologies. Cranio-mandibular size, form and shape are compared between parents and hybrids (N=634), as are frequencies of unusual non-metric traits. Morphometric analyses show that all first generation (F1) hybrids are intermediate in cranial and mandibular shape, and larger in size than the mid-parental mean, or sometimes even larger than parents. However, the expression of these differences in hybrids appears to be dependent on phylogenetic distances between parents, with sub-specific F1 hybrids often appearing transgressive (outside the range of both parents), and specific hybrids more intermediate. Subsequent hybrid generations (B1s and F2s) are highly variable in cranio-mandibular size and shape depending on the generation of the cross, possibly reflecting the degree of heterozygosity. B1s and F2s are highly variable, with examples of both parental morphologies as well as hybrid heterotic size being retained in some individuals. Models based on these data show that it is possible to detect hybridization in samples (as opposed to sampling sympatric non-hybridizing taxa) on the basis of morphological variability. In terms ofnon-metric cranial traits, hybrids are more likely to express unusual sutural anomalies and atypical bilateral foramina. Two specimens (intra-specific F1 and B1 individuals) showed extensive wormion bones. These data corroborate current research on hybrids, providing further evidence for the patterns seen in other animal hybrids. Furthermore, results of this study support morphological evidence for hybridization in several hominin specimens, including Oase II (cranium associated with a known multigenerational recombinant) and potentially other Middle Pleistocene hominins.
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    Population variation within the Iron Age of southern Africa: an assessment using dental anthropological and cranio-mandibular metric techniques
    (2013) Warren, Kerryn Ashleigh; Ackermann, R R; Hall, Simon
    Evidence for iron smelting, agriculture, elaborate pottery styles and increased sedentism appears abruptly in areas previously inhabited by hunter-gatherers and herders during the Early Iron Age (EIA) of southern Africa from around 250CE. Ceramic evidence connects these (cultural) populations to the second millennium Iron Age sites in eastern Botswana. This material culture differs from second millennium Late Iron Age (LIA) sites in South Africa which are attributed to migrations from east Africa and are connected, via the material culture, to modern Sotho-Tswana and Nguni speakers. Although the material culture of this period is well-studied, there is a gap in correlating Iron Age biological identity with the established cultural identity. Here I present an analysis of metric and nonmetric dental and cranial variation to better understand biological relationships among these samples. Specimens from the LIA, EIA and Eastern Botswana are compared with each other, and to specimens from Iron Age Zambian sites, modern Bantu-speakers and a historic Ndebele site from the midnineteenth century. This research indicates few differences between the EIA and LIA groups, although surprisingly a sample from eastern Botswana is more similar to the LIA group than the EIA group. The Iron Age samples are significantly different from the modern sample, while the historic sample lies intermediate to the Iron Age and modern samples, indicating that Iron Age peoples had a pattern of dental and cranio-mandibular variation that differs from what is seen in modern (admixed?) descendants. This research has important implications for our understanding of the sub-Saharan African dental complex, showing population differences within this complex (between Khoesan and Iron Age peoples) as well as variation over time (between Iron Age peoples and modern Bantuspeakers). This indicates that, while farmers within the Iron Age of southernmost Africa are generally homogenous, there are important differences between populations in sub-Saharan Africa that reflect complex and differing histories.