AAA2020 Virtual Conference Banner 7 - 10 Dec

Hard Science and Hard Tissue: Osteological Evidence for Human Behaviour and Biology

Angeline Leece
La Trobe University

Palaeoanthropology is limited in part by the nature of the fossil record. While most biological sciences can rely on representative population samples and complete individuals, palaeoanthropological questions must be answered using unique and novel ways of assessing biological processes and behavioural patterns. This session will demonstrate various analytical techniques and methods that can be used to answer palaeoanthropological questions. These include, but are not limited to, the use of magnetic resonance imaging to develop modern human models used for interpreting the morphology palaeo-populations, microstructural histology to infer functional adaption, extant modelling of sexual dimorphism and variation to interpret intra- and inter-specific variation, and actualistic archaeological experiments to infer hominin tool use. This session aims to highlight the work of PhD students and Early Career Researchers as they work to answer long standing questions about our ancient ancestors.

Paranthropus Robustus: The Dental Evidence. Does Variation in Size Represent Sexual Dimorphism?

Angeline Leece
La Trobe University

Co-Author/s
Martin, J.M.; Palaeoscience Labs, Dept. Archaeology and History, La Trobe University
Schwartz, G.T.; Institute of Human Origins, Arizona State University, Tempe, Arizona; School of Human Evolution and Social Change, Arizona State University, Tempe, Arizona.
Strait, D.S.; Department of Anthropology, Washington University, St. Louis, USA.; Palaeo-Research Institute, University of Johannesburg, Gauteng Province, South Africa.
Herries, A.I.R.; Palaeoscience Labs, Dept. Archaeology and History, La Trobe University; Palaeo-Research Institute, University of Johannesburg, Gauteng Province, South Africa.

Paranthropus robustus is an extinct megadont hominin that evolved a hyper-robust masticatory apparatus in response to an unstable climate at ~2.0 Ma in southern Africa. Although known from numerous sites in the Cradle of Humankind, South Africa, the majority of well-preserved Paranthropus robustus fossils come from the palaeocave sites of Drimolen and Swartkrans. The high degree of intraspecific variation, primarily regarding dental size, evinced by Paranthropus robustus has been interpreted as extreme sexual dimorphism and a pattern of secondary maturation. Consequently, Paranthropus robustus has been argued to have a gorilla-like harem social structure. Extant primate species with harem-like social structures tend to push young males out of the group early, resulting in increased predation of this demographic. This scenario has been proposed to explain the extreme sexual dimorphism in Paranthropus robustus and the preponderance of smaller specimens at Drimolen, and larger specimens at Swartkrans. This is because Swartkrans is argued to be a carnivore accumulation, preserving mostly males, whereas Drimolen has been argued to be a sleeping site, preserving mostly females and juveniles. We assess this hypothesis in light of new fossil evidence from Drimolen.

The Taxonomy of Paranthropus Robustus as Revealed by Fossils from Drimolen, South Africa

Jesse Martin
La Trobe University

Co-Author/s
Leece, A.B.; Palaeoscience Labs, Dept. Archaeology and History, La Trobe University
Strait, D.S.; Department of Anthropology, Washington University, St. Louis, USA.; Palaeo-Research Institute, University of Johannesburg, Gauteng Province, South Africa.
Herries, A.I.R.; Palaeoscience Labs, Dept. Archaeology and History, La Trobe University.; Palaeo-Research Institute, University of Johannesburg, Gauteng Province, South Africa.

Paranthropus robustus is an extinct, megadont hominin known from ~2.0 – ~1.6 Ma contexts in southern Africa. Well preserved crania have been recovered from the sites of Swartkrans and Drimolen, and less well-preserved specimens (including the type specimen TM 1517) have been recovered from Kromdraai. The southern African ‘robust australopithecine’ sample has generally been sorted into one taxon, P. robustus, although some researchers recognise the sample from Swartkrans as specifically distinct from Kromdraai. New fossils from Drimolen force a reconsideration of the taxonomy of P. robustus within a context of species concept theory. In particular, the recognition of diagnosably distinct sub-populations within hominin species lineages challenges conventional criteria for recognising distinct species in the fossil record. Thus, we propose additional criteria beyond ‘diagnosability’ as requisite to recognise a new species; specifically, it is necessary to falsify the null hypothesis that a new fossil samples part of an already recognised species lineage.

 

Revisiting the Microstructure of the Homo Erectus Trinil V and Trinil III Femora

Madeleine Green
Australian National University

Co-Author/s
Louys, J.; Australian Research Center for Human Evolution, Environmental Futures Research Institute, Griffith University, Brisbane, Australia
Argue, D.; School of Archaeology & Anthropology, Australian National University, Canberra, Australia
Miszkiewicz, J.; School of Archaeology & Anthropology, Australian National University, Canberra, Australia

Palaeoanthropology has historically relied upon the gross anatomical examination of fossils to answer questions relating to hominin evolution. Recent advances in the study of bone growth and adaptation now reveal complex macro- and microstructural relationships. This allows factors such as the biomechanics of an individual, their age, diet, sex, pathology; and taxonomic affinity to be better understood, potentially providing new insights into the ecology and systematics of extinct hominins. However histological sectioning in palaeohistological analysis is too destructive for regular use on rare specimens. In 1934 and 1937, Eugene Dubois pioneered palaeohistology in palaeoanthropology by non-destructive microscopic examination of the exposed internal Haversian lamellar bone tissue of the Trinil V Homo erectus femur. His work represents one of the first published examples describing osteon structures in an extinct hominin. Day and Molleson made thin sections of the Trinil III Homo erectus femur in 1973. Since then interest in the palaeohistology of palaeoanthropological specimens has increased and exciting new insights have been gained. A number of these sections are still available for study and overdue for re-examination and comparison in light of modern understanding of the functional adaptation of bone in response to factors such as biomechanics, age, diet, sex, pathology and taxonomic affinity. Here, we revisit the Dubois publications and Day and Molleson. We provide a comparison with modern Homo sapiens and other mammal experimental model histology by evaluating the qualitative and quantitative accounts of histological variables relating to biomechanics and taxonomic affinity provided by Dubois, and Day and Molleson, as well as their methods. This demonstrates how palaeohistology has improved as a discipline, and highlights what new information can be gleaned by cross comparing past palaeohistological work in palaeoanthropology with contemporary knowledge of bone biology.

Trusting Tall Tiger Tales: How big was the Thylacine?

Douglass Rovinsky 
Monash University 

Co-Author/s
Evans, A.R.; School of Biological Sciences, Monash University; Geosciences, Museums Victoria
Martin, D.G.; Pixelmind, Viskovo Croatia
Adams, J.W.; Department of Anatomy and Developmental Biology, Biomedicine Discovery Institute, Monash University,

Until its extinction, the thylacine was the largest extant carnivorous marsupial, but almost no data exist regarding its body mass. This leaves an enormous gap in our ability to reconstruct their ecology and the structure of the ecosystem it inhabited. The popularly-used mass estimate (29.5 kg) is based on sizes given in a handful of 19th Century periodicals detailing thylacines killed in rural Tasmania. However, no quantitative work has been done to validate these masses – are the historical records accurate, or were they tall tales exaggerating the thylacine’s size (and therefore danger) more indicative of human’s relationship with the animal than of reality? Here, we present new quantitative body mass estimates for 93 adult thylacines, including two taxidermy specimens and four complete mounted skeletons, using 3D volumetric model-informed regressions. We demonstrate that the prior view, based on the 19th C. periodicals, overestimated the average adult thylacine body mass by nearly 80%. Rewriting the body mass of the thylacine also rewrites our view of its ecology, helping reject the idea of a “wolf-like” niche and aligning with studies suggesting a diet of small animals – not large prey – for the thylacine. Historical reports, while invaluable sources, still must be critically evaluated, as farmers – just like fishermen – can tell tall tales.

Technology or Taphonomy? A Study of the World’s Oldest Bone Tools

Rhiannon Stammers 
La Trobe University  

Co-Author/s
Herries, A.I.R.; Palaeoscience Labs, Dept. Archaeology and History, La Trobe University; Palaeo-Research Institute, University of Johannesburg, Gauteng Province, South Africa.

The world’s oldest purported bone tool technology comes from a series of palaeocave sites in the UNESCO Fossil Hominid Sites of South Africa World Heritage Area, Gauteng Province, South Africa. The identification of these artefacts as bone tools is based on their gross morphology and an associated use-wear pattern. However, the authenticity of this technology is disputed. Excavations at Drimolen Main Quarry have identified fossils with a similar gross morphology to those published as bone tool from the palaeocaves in South African. Through comparative analysis of other faunal assemblages from fossil sites in South Africa, ethnographic collections, actualistic experiments, and utilising the concepts of traceology, a collection of 64 specimens from Drimolen Main Quarry and two specimens from Kromdraai B were identified, and confirmed, as bone tools. Recent dating and stratigraphic analysis of the Drimolen Main Quarry place the Drimolen Bone Tool Collection as the oldest recognised bone technology in the world.

Temporal Lobe Sulcal Pattern Variation in Modern Humans and Implications for Fossil Homo

Alannah Pearson 
Australian National University 

Co-Author/s
P. David Polly; Department of Earth and Atmospheric Sciences, Indiana University
Emiliano Bruner; Centro Nacional de Investigación sobre la Evolución Humana, Spain

Brain evolution involves changes in processing centres that are often marked by folds on the surface of the cerebrum including sulci and gyri. Sulcal variation is considered high in modern humans, but quantification is lacking. We assessed the degree of sulcal variation of some major folds of the temporal cortex using a sample of T1-weighted in vivo Magnetic Resonance Imaging (MRI) of the brain in 48 adult humans (male = 23, female = 25) which were generated into three-dimensional virtual models. Sulcal variants were identified for the posterior rami of the Sylvian fissure and the two segments of the superior temporal sulcus for the left (L) and right (R) temporal lobes. Considering small sample size and high individual variation, we determined an arbitrary number (≥ 15%) of individuals required per sulcal variant before calculating total sulcal variation as a percentage. Total variation differed between left and right temporal lobes for the posterior ascending ramus of Sylvian fissure (L = 74%: R = 67%) and for the posterior descending ramus of Sylvian fissure (L = 99%: R = 82%). Similarly, total variation differed between the left and right temporal lobes for the ascending segment of the superior temporal sulcus (L = 65%: R = 52%) and the horizontal segment of the superior temporal sulcus (L = 78%: R = 77%). These findings suggest greater sulcal variation for the right temporal lobe compared to the left for the rami of the sylvian fissure, however, sulcal variation in the segments of the superior temporal sulci were more widely spread. Ultimately, the identification of a higher prevalence of sulcal pattern variation on the right compared to the left modern human temporal lobes has implications for inferences of sulcal imprints in endocasts for fossil Homo.

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