Deb,

No - nobody has been attacked. This is an interesting discussion to have emerged from a deformed cow's tooth!

The word 'deciduous', when applied to human molars, has a long history of use in anatomy and anthropology.

Its use goes back certainly to Andrew Fyfe, who in his 'A Compendium of the Anatomy of the Human Body' wrote in 1800 "Five deciduous teeth . . . in each side of each jaw." (p.30). Obviously he is including m1 and m2 in this itemisation.

Thomas Henry Huxley, in his 1870 'Lessons in Elementary Physiology' wrote more specifically: "The cutting of this first set of teeth, called *deciduous*, or *milk teeth*, commences at about six months, and ends with the second year. They are altogether twenty in number - eight being cutting teeth, or *incisors*; four, eye teeth, or *canines*; and eight, grinders, or *molars*."

Presumably these authors are using the term 'deciduous' by analogy with leaves shed from trees. Anyway, that's how I have always thought of the word.

'Deciduous molars' is a term that continues to the present day among anthropologists and anatomists - as Hillson points out - even though we recognise the likely evolutionary origin of m1 and m2 teeth as premolars.

You say that a human m2 can in no sense be deciduous, and that there is no such thing as a deciduous molar because it is impossible by definition.

OK. So I guess that somebody must have appropriated the general term 'deciduous', and reapplied it to a narrower definition.

Do you know where this narrower definition of 'deciduous' was originally published?

Richard


On 6/10/2012 17:07, [log in to unmask] wrote:

Ahh, well, Richard, it's gallant of you but of course you don't have to
come to the defense of anyone, because no one has been attacked.

I probably did fail to make myself clear, however. The tooth in question
was a human second lower molar or m2. In my conversation with the
'confused' person, I was not speaking from some old-fashioned theory of
the evolutionary origin of that tooth, or any tooth, but merely stating
the correct fact that this tooth is one of two in each rear quarter of the
human jawbone that are not replaced. It therefore can in no sense be
"deciduous". To repeat: there is no such thing as a "deciduous molar"; it
is impossible by definition, because the only deciduous teeth are by
definition premolar, canine, or incisor teeth. That the tooth in question
is not replaced -- in other words, it develops in and erupts from a
'one-tooth alveolus' -- is what defines this tooth as a molar in the
technical (as opposed to the vernacular) sense.

Your response prompted me, of course, to go back to my library to check a
reference or two, and the happy result is that I am able to report an
error on p. 46 of the otherwise very helpful book "Teeth" by Simon Hillson
(Cambridge Univ. Press). The error is in Fig. 1.25, which shows deciduous
and permanent teeth in Homo. The error is that the labels for the lower
teeth have been switched -- i.e. the label that says "permanent lower"
actually shows the deciduous lower arcade. The labels for the deciduous
and permanent upper arcades are correct.

The tooth formula given on p. 44 of this book for humans is correct:

di2/2, dc1/1, dp2/2 ----> i2/2, c1/1, p2/2, m3/3

....and this is what, as I said before, I was trying to help my physical
anthro colleague to understand. Also as I said before: I sympathize, it is
easy to get mixed up. -- Dr. Deb

This is off topic, but let me come to the defence of the  physical
anthropologist that Deb conversed with.

The anthropologist spoke of a human tooth as a 'deciduous molar'.

Deb says she told the "confused" anthropologist that there are no
deciduous molars.

In saying this, Deb is following the evolutionary position that the two
human molariform teeth are adaptively evolved from premolars.

I want to make the point that the physical anthropologist, in terms of
nomenclature, was by no means confused. She is in step with functional
terminology widely used by English speaking physical anthropologists -
and dental anatomists, clinical dentists, orthodontists, etc..

The two deciduous grinding teeth are called 'molars', whatever the
evolutionary origin of these molariform teeth might be.

Richard


On 5/10/2012 05:58, [log in to unmask] wrote:

[snipped]

I go into this a little because it's a subject dear to my own heart; I
am
currently writing a textbook on equine dentistry, which I have been
researching for years. I have a great admiration for all
zooarchaeologists
but I also know, from talking with some anthro/archaeo graduates, that
they can be mixed up about some things. For example recently I had to
demur (for the sake of peace) in a conversation in which someone trained
in physical anthropology insisted to me that a certain human tooth
represented a 'deciduous molar'. She is confusing 'molar' in the sense
of
'cheek tooth' with 'molar' in its technical sense, i.e. molar vs.
premolar. When I told her there are no deciduous molars, that only the
premolar teeth are replaced, or again that there are 'one-tooth alveoli'
vs. 'two-tooth alveoli', she was surprised and confused because she also
has muddled the term 'pre' in 'premolar', confusing 'pre' meaning
anterior
in TIME with 'pre' meaning anterior in POSITION. I sympathize; it is
easy
for anyone to get mixed up when the information presented in most
existing
textbooks fails to convey an adequate mental picture. -- Dr. Deb

On 6/10/2012 17:07, [log in to unmask] wrote: