Lab 3: Mystery jawsAnt 274

IntroductionKNM-ER 62000 is the partial face of an adolescent hominin dating to between 1.9-1.95 mya. KNM-ER 60000 is a fairly complete mandible of an adult hominin dating to between 1.78-1.87 mya. Because the genus Homo and “robust” Australopithecus (A. boisei) are both known from this region and this time period, a preliminary research question we can ask about these fossils is whether they belong to Homo or A. boisei.

You will attempt to answer this question in this lab exercise, by collecting dental dimensions on a number of hominins. Before you can answer whether these two fossils belong to Australopithecus or Homo, you need to first demonstrate that these two genera can be distinguished from one another with dental metrics.

Your completed lab report must be uploaded to Moodle no later than12 November!

MaterialsYou will compare ER 62000 with other hominin maxillary teeth. As this specimen only preserves P4, M1 and M2, you will only collect data for these teeth in other fossils.

Similarly, you will compare ER 60000 with sets of mandibular teeth. This fossil preserves all adult teeth, from I1-M3: to reduce workload and avoid redundancy, measure only the left side of this specimen. For the other hominin fossils, try to measure all available teeth from only one side wherever possible; if teeth are present on one side but not the other, it is okay to switch sides in order to get data for each tooth type.

Only take measurements of buccolingual width, as mesiodistal lengths can be obscured by interproximal attrition (wear between adjacent teeth).

Instructions for opening files and collecting dental measurements (Methods)

Download each specimen listed in the accompanying data table. To open a file in MeshLab, make sure you have opened a new, empty project; a new empty project should be open when you start up MeshLab. Select “Import mesh” (either from the icon or the File menu) and find the specimen file you want to open.

When you select a file, MeshLab will ask if you want to “unify duplicated vertices” Select “OK.”

Once you can see the scan, you will need to orient it so that you can take the maximum buccolabial/labiolingual tooth diameter of each tooth. The specimen can

be rotated in 3D when the “Not Editing” icon is selected:

Lab 3: Mystery jawsAnt 274

You can zoom in and out with the mouse scroller. If you need move the specimen so that a different point is at the 3D spherical center, select the “Manipulator tool” icon and follow the instructions that appear in the top left corner to “translate” the specimen:

Once you have found a good view from which to take your measurement, select the “Measuring tool,” and click the two endpoints of the distance you wish to measure:

Be sure to check your measurement! Select the “not editing” icon to rotate the fossil but keeping your measurement. Be sure that you are measuring the two widest points on the tooth, and not elsewhere. You may need to take a few measurements before you get the best one:

Lab 3: Mystery jawsAnt 274

Note that for canines and incisors the measurement will look more “front-to-back” than “side-to-side”:

Once you are satisfied with your measurement, record it into the appropriate cell in the table and move on to the next tooth measurement. After you have entered all the data into your table, answer the following questions.

Lab report questionsFor your lab “report,” answer all of the following questions completely and using complete sentences.

1. Briefly state your research question.2. What data are you using to address this question? Explicitly state how they

address the question, and what observations you expect to make about the KNM ER 62000 and ER 60000 data (that is, what should they look like if a given scenario is true?).

3. For both the maxillary and mandibular dentition, briefly describe how Homo and Australopithecus boisei samples differ from one another.

4. Based on your data, do you think KNM ER 62000 represents A. boisei or Homo, and why? If you cannot distinguish, you must explain why.

5. Based on your data, do you think KNM ER 60000 represents A. boisei or Homo, and why? If you cannot distinguish, you must explain why.