Last Supper Hypothesis
Dr. Marion
are atleast two ways to compare microwear in different species. One is
to compare features observed with the SEM, such as pits and striations,
for directionality and density. The problem with such an approach is
that repeated wear obliterates details f previous wear patterns. This is
often referred to as the "Last Supper Hypothesis." Many proponents to
this feel that wear observed on a tooth will only contain clear evidence
of the last meal that tooth participated in masticating.
What are your thoughts on this?
By the way the other method is to compare wear on homologous facets as
supported and utilized in studies by Teaford and Walker.
wa...@mfs.duke.edu
expensive machine. None of the studies I have seen and read really show
anything with SEM. oooh, what a nice picture of a tooth -- neato!
I think the future lies in microbiology, histology,without the SEM.
w
wa...@mfs.duke.edu
Gerrit Hanenburg
>My posting concerns research involving dental mirowear. In general there
>are atleast two ways to compare microwear in different species. One is
>to compare features observed with the SEM, such as pits and striations,
>for directionality and density. The problem with such an approach is
>that repeated wear obliterates details f previous wear patterns. This is
>often referred to as the "Last Supper Hypothesis." Many proponents to
>this feel that wear observed on a tooth will only contain clear evidence
>of the last meal that tooth participated in masticating.
>What are your thoughts on this?
My thoughts:
The last meal will obliterate some of the wear patterns caused by previous
ones.The result will be overprojection leading to a complex mixture of
patterns caused by several consecutive meals.(comparable to the
overprojection of cutmarks on bone caused by carnivore teeth and stone
artifacts which have led to the conclusion that hominids were scavengers)
I don't think the information of previous meals is completely lost (up to a
certain limit of course) but it maybe more difficult to interpret.
If the species had a rather stable diet the different patterns will resemble
each other and so some loss of information of part of the previous patterns
will be less of a problem. But if it had a rather variable diet the problem
will be a bias towards wear caused by tough gritty material,leading to the
conclusion the it ate tough gritty food while in fact it also may have used
large quantities of softer material,as might have been the case in
Paranthropus.I think part of the solution is to compare the wear pattern on
the teeth of different individuals of the same species.This should give you a
reasonably accurate image of the overall diet of the species.(Assuming that
the chances of the last meal being the same in all individuals is rather
small)
Gerrit.
Gerrit Hanenburg
I wonder what studies you refer to.
Do you have any alternative method of extracting 3D information on microwear
patterns from fossil teeth that is superior to SEM?
Gerrit.
wa...@mfs.duke.edu
>The last meal will obliterate some of the wear patterns caused by >previous
>ones.The result will be overprojection leading to a complex mixture of
>patterns caused by several consecutive meals.
o interpret.
>If the species had a rather stable diet the different patterns will >resemble each other and so some loss of information of part of=
the >previous patterns will be less of a problem. But if it had a rather >variable diet the problem will be a bias towards wear cau=
sed by tough >gritty material,leading to the
>conclusion the it ate tough gritty food while in fact it also may have >used
>large quantities of softer material,as might have been the case in
>Paranthropus.I think part of the solution is to compare the wear pattern >on
>the teeth of different individuals of the same species.This should give you a
>reasonably accurate image of the overall diet of the species.(Assuming that
>the chances of the last meal being the same in all individuals is rather
>small)
>
>Gerrit.
I think these SEMs are still simply showing neat grooves and pits from
ages ago. I still cannot agree with you that dental microwear will "give
a resonably accurate image of the overall diet." Especially, when, as
you put it, teeth exhibiting a "tough gritty surface, will lead to a
conclusion that the diet was tough and gritty." What about
parafunctional habits, sand incorporated into foodstuffs, etc.? Don't
you think there is more to it?
w
Dr. Marion
>species.(Assuming that the chances of the last meal being the same in >all individuals is rather small)
>
>Gerrit.
>
Good point. Thanks for your input.
LRM
Gerrit Hanenburg
>I think these SEMs are still simply showing neat grooves and pits from
>ages ago. I still cannot agree with you that dental microwear will "give
>a resonably accurate image of the overall diet." Especially, when, as
>you put it, teeth exhibiting a "tough gritty surface, will lead to a
>conclusion that the diet was tough and gritty." What about
>parafunctional habits, sand incorporated into foodstuffs, etc.? Don't
>you think there is more to it?
The choice seems to be between:the microwearpattern will give you no
information about the diet of fossil species (your position?) and it will
give some information about the diet (my position).
Since teeth are mainly used in foodprocessing I think it's reasonable to
assume that most of the wearpattern is caused by the diet.After an animal
dies there will be no more occlusal events and since enamel is very resistant
to decay the pattern on the fossilized tooth acquired during life will be
preserved.(unless the tooth is badly eroded).So what you have is a
wearpattern caused by occlusal events during the animals life.
I agree with you that some wear may be caused by activities and processes
that are not directly related to diet (e.g.dental caries) but SEM can be
helpfull in distinguishing between patterns caused by these different
activities.Without the SEM you've got no image at all and you cannot even
begin to make inferences.
With SEM you can correlate microwear and diet in extant species with a known
diet so you have a basis of comparison for use with fossil species.
Thus I think the SEM image together with knowledge of the anatomy of the
masticatory apparatus,the mechanics of chewing and microwearpatterns in
extant species can give you a fairly accurate impression of what happened in
the occlusal plane of fossil species and,by inference,of their diet.
Even if there is no correlation between diet and wear you will need SEM to
arrive at that conclusion.
SEM is as valuable a scientific tool in trying to figure out what caused a
certain microwearpattern in fossil teeth as it is in inferring what caused a
certain pattern of microwear in extant species (with less certainty because
of the historical character of the fossil;you can't actually see what it ate)
The pits and scratches caused by sand incorporated into foodstuffs is
informative about diet.They tell you that the hominid in question possibly
ate sandy food like tubers and roots.But it would be wrong to jump to this
conclusion on the basis of only one specimen.If the same pattern recurs in
other specimens of the same species the conclusion is reasonably justified.
See also:
F.E.Grine,Dental evidence for dietary differences in Australopithecus and
Paranthropus;a quantative analysis of permanent molar microwear.
Journal of Human Evolution 15 (1986),p 783-822.
Gerrit.
Mrdubious
patterns on the teeth of living organisms, ensured you had a good idea of
(a) their overall diet and (b) their last meal, you might be able to
settle this debate. If you could find enough money.
Stuart Dubois
AskCambrix
a few scientifc basics are being taken for granted. The population is the
smallest sample size, not the individual. While microwear on one
individual may display certain patterns, it is preferable to have
concomitant evidence from at least the same dig, if not from all subjects
of the species, before making a reliable observation, which I believe Mr.
Grine et al have shown. Variation within the population is also of great
significance, and certainly leads to more questions.
SEM is simply a tool, as is a laent fingerprint in forensics. It is the
observations and interpretations of the investigator which decide what the
markings mean. SEM of its own accord is nothing but allows for greater
breadth by allotting a more indepth and concise picture. When all is said
and done, it is humans, not machines, studying humans.
Ronald E. Armstrong
R. & J. Vera
TESTING 1, 2, 3, THANK YOU, THIS WAS ONLY A TEST. I'll be back.
Joy
wally
>SEM of its own accord is nothing but allows for greater
>breadth by allotting a more indepth and concise picture.
>When all is said and done, it is humans, not machines,
>studying humans.
>
I couldn't agree with you more! I mean we have researchers counting pits
and scratches but there is more to it to that! Orientation of the
scratches for instance is very very important. Then their cusp location
(or fossa).
loum...@dolphin.upenn.edu
They have actually begun qualitative analyses of SEM features. See JDR
72: Abstract #1903, 1993. I am sure they are more but I know of this one
because it was done here at PENN.
Zenjackal
archaeological reseach sources such as electronic journals (so far all I
have found are web pages). If you have suggestions please e-mail me a
zenjackal.aol.com.
Thanks,
Dave