Anthropology 110 Discussion Section Name ______________________

Pre-Lab Early Fossil Record Section 2 3 4 5 6 7 8 9 10 11

Submit this activity in the meeting of your “Early Fossils” lab.

Our study of the primates introduced us to the potential of teeth as an indicator of morphology and the behavior of those animals. Teeth are similarly important in the study of fossil specimens; given the high preservation of teeth in the fossil record they are often an integral part of scientific analyses. While teeth themselves are informative, it is also important to consider them as components of our craniofacial skeleton and chewing musculature.

The two major muscles of mastication (chewing) are the TEMPORALIS and the MASSETER. Observe the location of these two primary muscules in the image at left. Place your hands on the sides of your skull (just in front of your ear lobes) and open and close your jaw. You should feel the temporalis muscle move under your fingers. Now shift your hands to the sides of your jaw and clench your jaw. You should feel the masseter contract under your fingers. The size, shape, and form of muscles can influence the size shape and form of the skeletal elements to which they are attached.In this prelab we will once again focus on processing several classes of food. This time, our emphasis will be upon the muscles you use to chew to gain an appreciation for the way food types can provide selective pressures for the evolution of various features of our musculoskeleton.

Select a food that meets the criteria of each column (soft, medium, and hard). WHILE YOU CHEW CONSIDER WHICH MUSCLES ARE WORKING AND HOW HARD THEY ARE WORKING. TAKE YOUR TIME CHEWING-we are interested in the act of chewing.

Food types

MusclesSOFT MEDIUM HARD

e.g. strawberry or other soft food that requires little chewing

e.g. Cheerios or other crunchy cereal

e.g. Carrot pieces or other hard food

Temporalis

Masseter

1) In each cell above describe the amount and degree of activity of both muscles as you chew the foods.

2) Which teeth do you use the most while chewing? Identify one of the four types in the cell at right..

3) What do you think the association is between molar size and jaw muscle size?

4) If you were to observe a fossil with large teeth and large boney areas where temporalis and masseter muscles attach, what might you conclude about the diet of that fossil hominin?

5) What might you conclude about the environment of that fossil hominin?

Adapted from Walker-Pacheco, 2010 Devlin