NOTES for WEEK 1 Hillson Text pp 1-67

These notes are intended to assist you in reading the text. Chapter 1 is just as the title says, an introduction. You will get a more systematic introduction in handout section 1.5 Introduction to Dental Anthropology.

Chapter 2 will be familiar territory for the clinician. The author has a companion text devoted to comparative anatomy entitled Teeth that may be helpful to you in doing your term paper.

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I. Who are the Hominids?

References are made to hominids such as Australopithecus and Paranthropus. We have not yet discussed them in this course. What are they? This section is a brief introduction to them with an emphasis on dental characteristics.

Hominids are modern humans and their upright walking ancestors. The earliest of them date back to more than four million years ago. The naming can be bewildering; however, their diversity illustrates an important issue. There is no single evolutionary line leading 'from ape to man.' Instead. There have been many different hominids. At times, two or more subspecies lived contemporaneously. You should think of them as branches like those on a bushy tree. All of the others died out; we are the sole survivors of the hominid line.

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II. Hominid Dental Characteristics

We can divide the hominids into three groups:

(1) Australopithecines, African hominids which include the earliest in our line: anamensis, afarensis, and africanus. They appeared more than four million years ago and seemed to have died out about 2.4 million years ago.

The dentition of afarensis retains primitive apelike features. The jaws are comparatively large and prognathous. The dental arch in the upper is 'omega' shaped; in the lower it is V-shaped. The teeth are large, but do not present the extremes seen in Paranthropus. The canines project beyond the occlusal plane. Diastema distal to the maxillary lateral incisors is present. The mandibular first premolar is described in the literature as 'commonly

unicuspid.'

In africanus, the incisors are spatulate and vertically implanted in the jaws. The canines are short and barely project beyond the occlusal plane. There is no maxillary diastema between the incisors and canines. The dental arch is more curved, like the modern human arch. The mandibular first premolar is described as 'bicuspid.' The molars are larger than in later hominids, but morphologically are very similar to those of Homo.

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(2) Paranthropus, the 'robust' African hominids which branched off about 2.7 Mya. They are known for their large cheek teeth and well developed chewing musculature. The last of these have been extinct for a million years.

The skulls of Paranthropus have prominent sagittal and nuchal crests associated with maximizing attachment areas for masticatory musculature. The term robust applies to those exaggerated skeletal and dental characteristics. Mary Leakey described her find of a Paranthropus in east Africa as 'Nutcracker Man.'

Paranthropus dental characteristics are distinctive. The incisor teeth are similar to africanus; however, the cheek teeth of Paranthropus are much larger than the anteriors. The premolars are molariform. The cheek teeth also had a thick covering of enamel and were subjected to considerable wear, implying a tough vegetarian diet. The heavy reinforcement of the face and the large attachments for the masticatory muscles confirm the tough diet.

These 'robust' hominids have massively built skulls and remarkably large cheek (premolars and molars) teeth. In the ones from east Africa, bucco lingual diameters of 22 mm have been recorded for lower third molars. Their anterior teeth, in contrast, are within the size range of our own.

The molars and premolars are enormous when compared to the incisors and canines. They are broad when compared to those of the Australopithecines. Maxillary third molars display wrinkled enamel, a characteristic seen in the great apes.

(3) Homo evolved in Africa 2.5 Mya and subsequently spread out around the world. The species are discussed here in chronological order. No attempt is made here to resolve disputes involving taxonomy and classification.

Homo habilis is considered to have been a more efficient biped than the Australopithecines. Most significant is its manufacture and use of stone tools. It has a greater cranial capacity, less massive jaws, and a smaller, less projecting face.

It has parabolic dental arches, small canines, no diastema, and a feature peculiar to H. habilis specimens, the relatively narrower (bucco-lingually) human-like cheek teeth.

Homo erectus is the first hominid with a wide distribution out of Africa into much of the Old World. The dentition of H. erectus is essentially similar to that of modern man. Its dental arch is parabolic. Compared to our dentition, the teeth are seen as larger, the maxillary central incisors are shovel-shaped, the canines are more robust, cingula are seen around the cheek teeth, and there may be some wrinkling of the enamel.

The mandibular second and third molars tend to possess five cusps rather than four cusps.

There is some degree of taurodontism wherein the pulp chamber extends well into the roots.

Neandertals are also frequently identified as Archaic Homo sapiens.

Their teeth are positioned more anteriorly than our own so that there is retromolar space distal to the third molars and anterior to the anterior border of the ramus. Anterior teeth are comparatively large. The molars are often taurodont, with the pulp chambers extending well into the root area.

The apparent great emphasis on the use of the anterior dentition resulted in a substantial mid facial prognathism.

The anterior teeth in many specimens exhibit wear patterns consistent with use of those teeth in softening animal hides.

Homo sapiens present with jaws that are less robust and the teeth a little smaller. There is a well-documented trend of dental reduction in the last 40,000 years. We will discuss this topic in a later article.

..... CJ '99

Resources

Berkovitz, B., Holland, G, and Moxham, B. Color Atlas & Textbook of Oral Anatomy Histology and Embryology. New York: Mosby Year Book, 1992.

Larsen, C., Matter, R., and Gebo, D. Human Origins The Fossil Record 3rd ed Prospect Heights: Waveland Press, 1998.

Wolpoff, M. Paleoanthropology 2nd ed. New York: McGraw-Hill, 1999.