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Human craniofacial evolution
I was involved in a description of late middle Pleistocene human
teeth from the palaeontological site of Hoedjiespunt 1, along South
Africa’s south-west coast.
I described a human incisor and cranial fragment from the Middle
Stone Age site of Pinnacle Point, along South Africa’s south coast.
For my PhD thesis I assessed craniometric variation in 153
individually dated human crania from South Africa with the aim of
investigating genetic continuity/discontinuity during the Holocene.
Evidence from the archaeological and/or skeletal record was used to
pinpoint likely episodes of genetic discontinuity. Craniometric data
were then used to assess whether genetic change had occurred. Two
periods of possible genetic discontinuity were identified: (i) c.
4000 BP, when an increase in overall population size, changes in
site organization and diet, and reduced mobility, were accompanied
by reductions in stature; (ii) c. 2000 BP, when herding was
introduced into the region. Results indicate that there was a
noticeable decrease in cranial size and concomitant size-related
changes in craniofacial shape between c.4000 BP and 3000 BP. This
was followed almost immediately by a recovery in craniofacial size
and a return to pre-4000 BP craniofacial shape at c. 3000 BP. This
recovery continued gradually, extending into the herder period
without any major shifts in morphology at 2000 BP. It is proposed
that the fluctuations in craniofacial size/shape were related to
changes in environmental factors, possibly nutritional
insufficiencies. Results obtained are consistent with long term
continuity in South African Later Stone Age populations during the
Holocene.
I am currently involved in several projects aimed at determining the
phenotypic origins of southern Africa’s Khoesan people.
After the completion of my thesis I was involved in post-doctoral
research on craniofacial variation in Nubian populations (pre-Meroitic
to medieval Christian periods) at the Univerisity of Paul Sabatier
(Toulouse 3) in Toulouse, France. This post-doctoral research was
funded by the European Virtual Anthropology Network (EVAN) which focuses on using new morphological analysis methods to
elucidate human origins.
Ecomorphology
I am in the process of setting up a research project focusing on
ecomorphological investigations of several large mammal species from
Langebaanweg. The ecomorphology of a fossil species is exemplified
by its overall body shape and size, skeletal and dental anatomy,
dental wear patterns and stable isotopic signals. This type of
information is used to deduce diet, locomotion, positional and
social behaviour, foraging strategies and preferred habitat.
Ecomorphological data gathered from individual fossil species may be
combined to recreate aspects of past ecologies. These are essential
to our understanding of the ecological contexts in which our
earliest ancestors evolved and provide biological information on the
animals that existed at the time.
This project follows on from and expands on previous
ecomorphological studies by employing a battery of methods (e.g. a
study of morphology, isotopes, microwear and mesowear) to all
studied species. It is hoped that this approach will provide precise
ecological data on each of the studied species. The study will not
only be limited to ungulates, as in many previous studies, but will
also include other groups such as carnivores. The eventual aim of
this study is to combine the data from individual species to
reconstruct aspects of the Langebaanweg large mammal paleoecology as
accurately as possible e.g. the niche separation between the
Langebaanweg hyaenid species.
Ungulate diets and environmental change
The Fynbos biome gets its name from the indigenous sclerophyllous
shrublands or “fynbos”, which occur throughout. Fynbos species are
characteristically hard, woody, tough shrubs, often with narrow,
leathery leaves. Although indigenous grasses are scarce, those
species that do occur are overwhelmingly of the cool growth season
C3 type. Fynbos did not always dominate the biome though. Fossil
evidence indicates that prior to the Holocene, grazing animals far
outnumbered browsers. This is specifically the case at sites such as
Elandsfontein and Duinefontein. The predominance of grazers suggests
that extensive grasslands dominated the region at the time. Although
Fynbos (as we know it) was probably present in the region since the
early Pliocene, it apparently only became dominant during the
Holocene, as suggested by the predominance of browsers over grazers
during this period.
The dietary determinations of Fynbos ungulate species have primarily
been based on taxonomic uniformitarianism, a method grounded in the
assumption that fossil taxa exhibited the same ecological
preferences as their nearest living relatives. This method has
several problems though. Firstly, it assumes that taxonomic groups
remained ecologically constant through time. This is not always the
case, as indicated by ecologically related temporal shifts in the
diets of some bovid taxa. Secondly, fossil occurrences from the
Miocene to Pliocene and Pliocene to Pleistocene are dominated by
extinct taxons, some of which do not have any historic descendents
on which to base dietary reconstructions. In order to generate taxon-independent
dietary evidence, I am in the process of setting up several projects
which employ more empirical methods of dietary determination
(isotopes, mesowear, microwear). This information will be used to
test previous palaeoenvironmental reconstructions.
Fieldwork
A new excavation at Langebaanweg is being planned in conjunction
with colleagues from the National Museum Bloemfontein for the 2008
field season. This excavation will focus on exposing an area which
previously produced remains of the famous Agriotherium africanum
skeleton. |
