Re: Microwear afarensis = gorilla. Pioneering work by Puech.

On Sep 23, 9:11 am, Marc Verhaegen <m_verhae...@xxxxxxxxx> wrote:

Dental microwear and paleoanthropology: cautions and possibilities


[web.pdx.edu]

"Usewear must be considered a probabilistic science, and as in other
realms of anthropological and archaeological inquiry, it is necessary
always to use multiple, independent lines of evidence to make the best
case for a given argument."




M Teaford

Center for Functional Anatomy and Evolution, John Hopkins University School
of Medicine, Baltimore, MD (USA)

Fifty years ago, investigators realized they could gain insights into jaw
movement and tooth-use through light-microscope analyses of wear patterns on
teeth. Subsequent work rekindled interest in the topic, as many workers
shifted to using the scanning electron microscope. Since then, numerous
analyses of modern and fossil material have yielded insights into dietary-
variations within and between species, and new perspectives on the evolution
of tooth use and diet in animals ranging from dinosaurs to human ancestors.

However, these analyses are not without their problems. Specifically, sample
sizes are small, and SEM images are so complicated that analyses are
difficult and time-consuming. Thus, we are only beginning to get a clearer
picture of the dental microwear of the early hominids.

Pioneering work by Walker and Puech suggested qualitative differences in
dental microwear between early hominids, but it wasn¹t until Grine¹s
analyses of the South African australopithecines that we began to see
quantitative, statistical evidence of such differences ­ with the robust
australopithecines showing evidence of a harder, more abrasive diet than the
gracile australopithecines. Subsequent work on the anterior teeth, by Ryan
and Johanson, and by Ungar and Grine, gave further insights into tooth use
in the early hominids, with, for example, the gracile australopithecines
showing evidence of heavier incisor use than the robust australopithecines.
Recent quantitative analyses have (1) reaffirmed Ryan and Johanson¹s
suggestions that Australopithecus afarensis shows microwear patterns
indistinguishable from those of the modern gorilla,

What foolishness, Verhaegin and Puech (2002) could not distinguish
microwear between a semi-aquatic mammal (capybara) and a land mammal
(mountain beaver). So much for distinguishing tooth wear between
species. Like tooth wear can be obtained from different diets.


and (2) shown that the
earliest members of our genus may also be distinguishable from each other on
the basis of their molar microwear patterns.

While this work is promising, and hints at the possibilities of moving
beyond standard evolutionary-morphological inferences, into inferences of
differences in tooth use between known individuals, there is still a great
deal of work to be done.

Right, first doughboy needs to lean which animals are aquatic and
which are terrestrial.

For instance, we still know far too little about
the causes of specific microwear patterns, either through laboratory studies
or fieldwork. Similarly, we still know surprisingly little about variations
in dental microwear patterns (e.g., between sexes, populations, and
species). In the face of such challenges, SEM-analyses may be reaching the
limits of their usefulness, as researchers strive for quicker, more
objective analyses of larger samples. As a result, two methods are beginning
to catch attention as possible ³next steps² in the evolution of dental
microwear analyses.

Solounias and Semprebon have advocated a return to lower magnification
analyses, using qualitative assessments of microwear patterns viewed under a
light microscope. The advantages of these analyses are that they¹re cheap
and fast, and may easily distinguish animals with extremely different diets.
The disadvantages are that they¹re also subjective, they can only detect
extreme dietary differences, and they may not be able to detect artifacts on
tooth surfaces.

Ungar et al. have begun scale-sensitive fractal analyses of data from a
confocal microscope. Advantages include the ability to quickly, objectively
and repeatedly characterize wear surfaces in 3D over entire wear facets, at
a wide range of magnifications. The main disadvantage lies in the newness of
the technique and challenges imposed by developing such cutting edge
technology. Also, it remains to be seen how results compare with those from
more traditional SEM analyses.With such new approaches, however, we may
finally have the tools to take dental microwear analyses to new levels of
inference.


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