john hawks weblog

paleoanthropology, genetics and evolution

mesial

  • Canines

    Mon, 2011-10-17 23:27 -- John Hawks
    Synopsis: 
    Lab exercise introducing canines, including sizes of maxillary canines in hominoids.

    The canine teeth in humans range from pointy-shaped to incisor-like in shape. There is only one canine in each quadrant, and it is the third tooth just distal to the incisors.

    Upper canines are often denoted UC and lower canines are then LC (so that the left lower canine is LLC.

    In many other primates, the canine teeth project out far beyond the others. There is often a large space, or \term{diastema} between the upper canine and the lateral incisor. For many species, the canine teeth are the largest difference between male and female skulls.

    This station has the skulls of several kinds of primates. Measure the height of the right canine tooth in each maxillary dentition. This measurement is taken from the tip of the canine to the base of its enamel.

    Then measure the breadth of the first molar.

    Your assignment is to make a plot showing how canine height relates to molar breadth in this sample of primates. Are there any outliers in your plot?

    Are there any other features of the mandibles that seem to correlate with canine breadth?

    Study terms: 
    canine
    mesial
    distal
    buccal
    lingual
    labial
    Tags: 
    Anthropology 105
    explainer
    laboratory
    teeth

  • Molars

    Tue, 2011-10-11 08:01 -- John Hawks
    Synopsis: 
    Laboratory exercise to introduce the terminology and anatomy of the molars.

    The most distal teeth are molars. Most humans have three molars, but many — especially in America — have their third molars (called wisdom teeth) extracted. Some people do not develop third molars at all, or they never erupt into occlusion. Molars have three or more cusps, and are used as grinding teeth.

    The upper molars are typically labeled with superscript numbers M1, M2, and M3, the lowers with subscript numbers M1, M2 and M3. Hence, the left lower first molar becomes LM1.

    Teeth have different directional terminology, referring specifically to the tooth row and the mouth. The direction toward the center front of the tooth row is mesial, and toward the rear of the tooth row is distal. For molars and premolars, the direction toward the cheek is buccal, and in toward the tongue is lingual.

    The two incisors, one canine, two premolars and three molars on both top and bottom are called the human dental formula. We write a dental formula as follows:

    2 1 2 3
    ___________
    2 1 2 3
    Study terms: 
    molar
    distal
    mesial
    buccal
    lingual
    dental formula
    Tags: 
    Anthropology 105
    explainer
    laboratory
    anatomy
    teeth

  • Premolars

    Tue, 2011-10-11 07:37 -- John Hawks
    Synopsis: 
    Laboratory exercise to familiarize students with premolars in the dentition.

    The premolars are directly distal to (behind) the canines. Generally there are two premolars in each quadrant. Counting backward from the front of the jaw, there are normally two adult incisors, one canine, and then the two premolars, making them the fourth and fifth teeth in each row.

    In anthropology, we number these teeth differently from dentists, because the premolars in humans are homologous with the distal premolars in other mammals. So the human premolars are called the third and fourth premolars, even though we have only two of them! The lowers are numbered P3 and P4; the uppers P3 and P4.

    Premolars usually have two distinct points, or cusps, on their occlusal surface. In humans the lower third premolar is sometimes shaped very much like a canine tooth with only one cusp. In many primates, the P3 has only one large cusp that cuts against the distal edge of the upper canine, like a scissors.

    Examine the premolars at this station, both upper and lower. Learn to distinguish these from the other teeth.

    The two incisors, one canine, two premolars and three molars on both top and bottom are called the human dental formula. We write a dental formula as follows:

    2 1 2 3
    ___________
    2 1 2 3
    Study terms: 
    premolar
    distal
    mesial
    dental formula
    cusp
    Tags: 
    Anthropology 105
    explainer
    laboratory
    anatomy
    teeth
Subscribe to mesial

Neandertals

For years, I've worked on their bones. Now I'm working on their genes. Read more about the science studying these ancient people.

Denisova

From a finger bone of an ancient human came the record of a completely unexpected population. My lab is working on the science of the Denisova genome.

Acceleration

The advent of agriculture caused natural selection to speed up greatly in humans. We're uncovering some of the ways that populations have rapidly changed during the last 10,000 years.

Malapa

Just outside Johannesburg, the Malapa site is producing some of the most exciting finds in human evolution. This site is the headquarters of the Malapa Soft Tissue Project.