The former curator of the Museum, Dr. Robert Broom, discovered a very
famous hominid fossil in the first part of the 20th century. The fossil came
from Sterkfontein Cave and was attributed to the genus Australopithecus
africanus (STS 5). The fossil was important because it signified that
an earlier discovery of a juvenile Australopithecus africanus at Taung was,
indeed, ancestral to the human line. The fossil is affectionately known
as 'Mrs. Ples' (a shortened version of the word Plesanthropus, the original
genus name of STS 5). Numerous other important fossil specimens can be found
at the Transvaal Museum. The Museum also has an important collection of
penecontemporary fossil fauna found among the hominid sites. The large collection
of baboon fossils (Parapapio broomi, Parapapio whitei, and Parapapio
robinsini) is one of the main reasons that I wanted to visit the Museum.
I first started working with the museum's Parapapio and hominid collection
as an undergraduate, when I began to examine the Sr/Ca ratios of australopithecines
and baboons from Sterkfontein. Organisms discriminate against strontium
in favor of calcium during metabolism. The basic notion is that their is
a trophic level effect in strontium discrimination as you move up the food
chain. Plants will have the highest Sr/Ca ratios and carnivores will have
the lowest. Therefore, it should theoretically be possible to distinguish
the amount of meat consumption in the diet of animals that are part of a
local food web (comparisons must be made within a food web because Sr/Ca
ratios fluctuate on various geological substrates). For a full review of
the principals and theoretical foundations of Sr/Ca research, please visit
my Sr/Ca research page. Previous studies by Sillen and colleagues (1992,
1995), investigated the Sr/Ca ratios of hominids from South Africa. My research
was intended to build on Sillen's earlier analysis and to address a number
of factors that may explain Sr/Ca variability between different animals and
animal groups, other than diet. Some of these factors that might explain
the variance in Sr/Ca ratios include differences in the types of plants consumed
(different plants have different Sr/Ca ratios), differences in the plant
parts consumed (leaves have lower Sr/Ca ratios than roots), differences in
geological substrates (animals may migrate from one substrate to another),
and differences in the discrimination of strontium by sex (males and females
discriminate against strontium at a different rate) and age (juveniles do
not discriminate against strontium as much as adults).
Sillen studied a group of nine individuals attributed to Australopithecus
robustus, along with two Homo sp. and found that the nine A. robustus samples
had lower Sr/Ca ratios than the Homo sp. Even after excluding one of the
Homo sp. (it was most likely a juvenile) the pattern seemed to remain. Theoretically,
this would imply that the earlier hominid group, Australopithecus robustus
(considered by many to have been a vegetarian (Robinson 1965), was actually
eating more meat than the Homo specimen. While stable carbon isotope ratios
do suggest that Australopithecus robustus was, indeed, eating some meat
and was most likely an omnivore, the suggestion that these individuals were
eating more meat than later Homo may be erroneous. Sillen suggested that
the reliance on tubers and underground plant products may have altered the
Sr/Ca ratios of the Homo specimens. Thackeray (1992) has also suggested
that sex differences may also explain the variation between the two groups.
It was this notion that I became interested in and with samples
obtained from the Transvaal Museum, I proceeded to test the relationship
of sex and Sr/Ca discrimination among a large sample of Parapapio broomi
fossils (baboons) from Swartkrans Cave. The samples had been morphologically
attributed into two groups, males and females, in C.K. Brain's 1981 monograph
on the site. Samples were analyzed in the Geology Department at the University
of South Florida, with the help of Professor Jeff Ryan. Currently, we are
still interpreting the results of this study.
The visit to the Transvaal Museum allowed me the opportunity to
further explore the sexual attributions of the P. broomi samples in my study
and to examine the sex of the Australopithecus robustus samples used in Sillen's
earlier analysis. At the museum I first examined all of the Parapapio broomi
specimens from which small samples had been taken for my study. I measured
all available teeth from these specimens and took notes regarding their morphology.
I then measured the teeth of every Parapapio broomi from Swartkrans that
is available at the Transvaal Museum in order to create a large comparison
sample. I then examined the hominids used in Sillen's earlier analysis, taking
tooth measurements and collecting data on other metric and non metric characters.
I then proceeded to collect additional data from other Swartkrans hominids.
I am now conducting statistical analysis to predict the probability that
each baboon is a male from my study and then to predict the probability that
the Australopithecus robustus samples in Sillen's study were male. The statistical
analysis and results from the DCP analysis, should clearly explain possible
sex differences in Sr/Ca discrimination.
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An Australopithecus family
group is depicted on the left, while a group is
depicted below scavenging animal remains (not the presence of the juvenile in the the tree, signifying that these hominids still spent some time on the ground and in the leaves. To the left (below), a hominid becomes the hunted, not the hunter. Early in the 20th century, Raymond Dart believed that groups of hominids hunted large carnivores, however, subsequent work dispelled that notion and C.K. Brain was in charge of creating this more appropriate representation. 
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