This debate started after Deb described a physical anthropologist as
confused, because she had insisted on describing a human tooth as a
'deciduous molar'.
In my first comment I said that "Deb is following the evolutionary
position."
To my surprise Deb then denied this, but the more I read her arguments
the more convinced I am that this is the case.
I am an evolutionist, and would follow the terminology relevant thereto
if I was, for example, giving the human dental formula in the broader
context of comparative mammalian anatomy.
But there are two contexts in which we operate - the evolutionary and
the descriptive. We slip between one and the other in our thinking.
Terminology in the two contexts differs slightly.
At the descriptive level, as I previously pointed out, the use of the
term 'deciduous molars' goes back to Huxley. It is unambiguously correct
in the context of comparative anatomy within the genus Homo.
Likewise (to refer to a point Terry O'Connor made about consistency) the
terms 'first/second premolars' make perfect sense in the context of
descriptive comparative anatomy within the genus Homo. The evolutionary
terminology of 3rd and 4th premolars makes sense within the context of
comparative vertebrate anatomy and evolutionary studies.
However I contend that 3rd and 4th premolars is an evolutionary
terminology that is confusing when applied, at the descriptive level, to
the jaw of a member of the species Homo.
As an analogy, consider this example. Tetrapods have forelimbs and
hindlimbs, with each limb carrying a foot. In evolutionary terms, I am a
tetrapod. I have what can be readily recognised, in an evolutionary
sense, as forelimbs and hindlimbs. Should I therefore, at the level of
descriptive anatomy, decline to refer to my arms and hands - in the name
of consistency?
One thing I missed in your last reply, Deb, was when and why the use of
the word 'deciduous' (in the sense of shed) teeth was redefined to
exclude m1 and m2 in humans. You discussed some important evolutionary
anatomists, but I was wondering whether you had any citation.
One final point. You say "no mammal has more than 3 molar teeth". Should
I tell the next kangaroo I meet that it is confused if it thinks it has
a fourth molar? :)
Richard
On 9/10/2012 05:47, [log in to unmask] wrote:
> To reply to both Richard and Terry concerning the terminology for teeth --
> first, as to Richard's question as to 'how far back' does the correct
> usage of 'molar', 'premolar', and 'deciduous' go -- the answer is that
> among vertebrate paleontologists, it goes back to when the embryology of
> teeth was figured out in the middle of the 19th century, so that by the
> time of the publication of William King Gregory's comprehensive two-volume
> "Evolution Emerging" (1951, MacMillan & Co.), he could refer to the
> "Cope-Osborn theory of dental formation".
>
> This takes us back to all the works of Henry Fairfield Osborn, which span
> from about 1880 to about 1920, in which the terminology is used correctly
> along with discussion of the "tritubercular theory", which allows us to
> trace the identity not only of the various teeth but the cusps of the
> teeth. Their work was contemporary with that of another excellent
> paleontologist, William Berryman Scott, whose still-relevant textbook "A
> History of Land Mammals in the Western Hemisphere" (1913, MacMillan) also
> uses tooth terminology correctly. To take it the last step back, we have
> the brilliant (my hero) Edward Drinker Cope, and my fellow K.U. man Samuel
> Wendell Williston. Cope's prolific output came in the 1860's through
> 1880's, along with his famous rivalry -- the "bone wars" -- with Othniel
> C. Marsh. Williston was active a little later, during the 1880's and
> 1890's. All of these men used the tooth terminology correctly.
>
> Now, the correct usage of the term "molars" as meaning "teeth that are not
> replaced" or "teeth that come from an alveolus that only develops one
> tooth-bud" is crucial to our being able to "count" the teeth, in other
> words to write the correct tooth-formula, for any mammal. The really
> difficult ones are those that have reduced dentition, i.e. for example
> sloths or cats, and those that have more teeth than occur in a 'normal' or
> 'standard' placental, i.e. more than I3, C1, P4, M3. Thus in working with
> an opossum, for example, the safest thing to do is to count forward from
> the last molar, because no mammal has more than 3 molar teeth, so that any
> tooth that has more than one cusp that lies ahead of the 1st molar (that
> is the third one counting forward from the back) but behind the canine is
> likely a premolar. Of course, if we were working with a newly-discovered
> species rather than a well-known one like Didelphis virginianus, we would
> ideally like to get a series of juveniles in order to XRay their jaws in
> order to confirm which of the alveoli contain permanent premolars
> developing beneath the deciduous ones.
>
> Likewise, it is very helpful to know that across the whole of the
> Carnivora, the carnassial teeth are superior P4 over inferior M1 in the
> permanent dentition. Especially in cats, where most of the molars do not
> develop, this will assure correct identification of all the teeth. Of
> course, again, we know this because embryological and/or XRay studies
> prove which alveoli contain two tooth-buds and which contain only one.
>
> So well-established is this understanding of tooth terminology/tooth
> embryology, that for example on p. 363 of Scott's 1913 textbook there is
> an illustration of the dentition of the Collared Peccary in which only
> I3/3, C/C, P2/2, and M1/1 are labeled. Having done this, the rest of the
> teeth do not have to be labeled.
>
> Gregory's "Evolution Emerging" is contemporary with the old standard Vert.
> Paleo. textbook, which is Alfred Sherwood Romer's "Vertebrate
> Paleontology" (with the first edition in 1933, Romer continued to update
> it with new editions, reflecting new finds, until the mid-1970's). His
> "Vertebrate Body" that I have already cited in a previous memo in this
> thread contains an excellent explication of the development of the
> mammalian skull, tritubercular theory, and standard tooth terminology.
>
> The other branch of natural science which naturally concerns itself with
> this business is Mammalogy, and the best-used textbook there is the one by
> Terry A. Vaughan (1972 and later editions, W.B. Saunders & Co.). There is
> an excellent illustration on p. 17 of my 1972 edition showing skull parts
> and tooth identities, and the discussion of tooth and cusp evolution and
> identity (largely taken from Romer) spans pp. 18-21.
>
> Now, as to Terry's query about whether we can ever hope to get human
> dentists to refer to the human premolar teeth as P3/3 and P4/4, the answer
> to that is no -- because human dentists are in this game for quite
> different reasons than we zooarchaeologists are. There are numerous
> different systems for numbering teeth (look in Ash's "Wheeler's Dental
> Anatomy, Physiology, and Occlusion" 1993, W.B. Saunders if you want to see
> all of them). The reason for the existence of each of these systems is to
> facilitate communication between professionals working on the teeth.
>
> In human dentistry, the widely-used Palmer system of notation first thinks
> of a person's head facing toward the dentist. Then the system divides the
> tooth-bearing parts of the skull into four quadrants, which are numbered
> with Roman numerals, left upper I, right upper II, right lower III, left
> lower IV (going clockwise around the 'muzzle'). It then numbers the teeth
> beginning with the central incisors, 1 through 8 (or more). For example,
> the maxillary right first molar is designated II-6 (or sometimes just
> "6").
>
> Analogous to this we have the Williams system of notation in equine
> dentistry, which works the same way. By this system, a horse's right
> superior canine tooth is called II-4, its right inferior 2nd premolar
> III-6, and its left superior 2nd molar is I-10.
>
> Both of these systems completely ignore what we know about the evolution
> and embryology of teeth, and thus completely obscure it. I find that many
> equine dentists indeed know very little about how teeth got to be where
> they are or how they came to have the form they have in whatever species;
> and for this reason I find much confusion among them when there is an
> anomaly such as a supernumerary tooth, a dentigerous cyst (an 'ear
> tooth'), or a twinned tooth. Nor have they any knowledge of cusp
> nomenclature or the development of hypsodonty or lophodonty. But, you see
> that it does not really have to matter to them, because their job is not
> to explain teeth but to treat or extract them.
>
> Nonetheless I do consider the system that we use, i.e. where the basic
> placental tooth formula is dI1-3, dC/C, dP1-4 followed by I1-3, C/C, P1-4,
> M1-3 to be superior, and I would strongly advocate its continued use at
> least among mammalogists, vertebrate paleontologists, physical
> anthropologists and zooarchaeologists. The reason I consider it superior
> is that it does not preclude us from understanding the simpler
> 'functional' numbering systems used by dentists, while allowing us insight
> as to how teeth develop and what might go wrong with the normal
> developmental sequence.
>
> I want to close by highlighting something that Terry mentioned, that some
> wellknown, influential, and otherwise excellent teacher of physical
> anthro. consistently mis-used the term 'molar', i.e. he used it in the
> vernacular sense, which terms any tooth behind the canine a 'molar'
> because all such teeth are (more or less) 'grinders' in humans. This is
> the usage of the farmer, rancher, and countryman. As I mentioned in an
> earlier memo, I have seen this error or 'sloppy language' from some
> others, particularly in equine dentistry. Vernacular usage is not wrong
> any more than vernacular usage of other words is 'wrong'; but it becomes
> dangerous when the teacher himself does not know any better, because it
> will get students who want and need a perfectly clear understanding into
> trouble. One of my maxims is that "sloppy language implies muddy
> thinking". Even the human dentist does not refer to the premolar teeth as
> 'molars' except possibly in casual conversation with a patient whom he
> thinks cannot understand anything more technical. With the better-educated
> patient he may go into 'unicuspids', 'bicuspids', and 'tricuspids', which
> is also rather an undefined, and certainly an antique, terminology. I
> think that we are best off being careful to use the terms 'premolar' and
> 'molar' as correctly as our forebears Cope, Marsh, Williston, Osborn, and
> Romer have taught.-- Dr. Deb
>
>
>
>> Well, since you raise the subject....
>>
>> I am with Deb on this one. Granted the term 'molar' has taken quite a
>> range
>> of meanings over the years, both technical and vernacular, and yes,
>> Cornwall (who got me started in animal bones) used to talk about
>> 'deciduous
>> molars', but then he was always more at home with bones than with teeth.
>> We
>> accept that some terms that are in vernacular use may have a more
>> restricted technical definition: 'soil' is a good example. Defining molars
>> by their 'grinding' function has a sort of logic when applied to people
>> and
>> badgers, though less so when applied to horses (in which the premolars do
>> just as much grinding) or cats (in which the few molars do not grind at
>> all). So an ontogenic definition, by which premolars have a deciduous
>> precursor and molars *sensu stricto* are only present in the permanent
>> dentition, seems to me to make an important distinction and to be worth
>> maintaining.
>>
>> And while we are at it, can we persuade our human osteo colleagues (and
>> dentists) to stop referring to the human premolars as 'first/second
>> premolars'? We Old World primates have only 3rd and 4th premolars in each
>> quarter-jaw, having got rid of the 1st and 2nd long, long ago in an
>> evolutionary clade far away. Even the prosimians lack a 1st premolar, and
>> I
>> like to think that I am somewhat derived relative to an Eocene notharctine
>> primate.
>>
>> So what do you think are our chances or getting consistent dental
>> terminology into physical anthropology?
>>
>> Terry
>>
>>
>> Terry O'Connor
>> Professor of Archaeological Science
>> Department of Archaeology, University of York
>> Biology S Block, Heslington,
>> York YO10 5DD
>> +44-1943-328619
>> http://www.york.ac.uk/archaeology/staff/academic-staff/terry-oconnor/
>>
>> And see the blog at
>> http://zooarchatyork.wordpress.com/author/zooarchatyork/
>>
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