CASE TEACHING NOTES
for
"Dem Bones: Forensic Resurrection of a Skeleton"

by
Alease Bruce
Department of Health and Clinical Sciences
University of Massachusetts Lowell

INTRODUCTION / BACKGROUND

This case is based on actual investigative procedures in The Use of Forensic Anthropology (Pickering and Bachman 1997). The case was developed for use in a freshman-level human anatomy and physiology course, It could also be used in biology, anatomy, and anthropology courses.

The student activities that accompany the case simulate some of the actual procedures that are conducted in a forensic anthropologist's lab. Students learn to identify bones, landmarks, and anatomical features associated with sex, age, height, and pathology. The activities are distributed with the case and can be completed within a two- to three-hour lab. The entire case and related activities can be completed within two three-hour labs, but I always expect students to devote additional out-of-class time to master the objectives.

Objectives

• To analyze the individual bones of the skeleton and their landmarks.
• To determine the sex of a skeleton from pelvic morphological distinctions.
• To determine the sex of a skeleton from skull morphological distinctions.
• To analyze bones to determine height estimations.
• To estimate the age of bones of individuals based on morphological changes.
• To evaluate bones for pathological and physiological changes.

Activities

• Activity 1: Bony Landmark Analysis

The markings included in this activity can be modified to include those that you require your students to learn. The complete list I use for this activity covers just about every disarticulated bone of the body, including the humerus, thoraic vertebrae, tibia, sacrum, scapula, femur, fibula, ulna, clavicle, lumbar vertebrae, patella, radius, cervical, sternum, ribs, carpals, phalanges, tarsals, sphenoid, temporal, mandible, and ethnoid. Although the skull is usually found intact, I include the disarticulated skull bones so that students acquire practice identifying them.


In completeing this activity, the students in effect generate a practice exam (a set of labeled bones for their out-of-class review). While the students work on this activity in groups, I circulate around the room checking their progress to verify that they have correctly identified the bones and landmarks.

Go to Activity 1 Handout

• Activity 2: Sex Determination from Pelvic Morphology

This activity asks students to help the anthropologist determine the sex of the skeleton. Morphological characteristics of the pelvis and skull are used in determining the sex of a skeleton. Pelvic differences are associated with adaptations for child bearing and the size of muscles. This activity also helps students to realize that pelvic girdles will not necessarily exhibit all female or all male characteristics. Based on their assessment, students must make a determination.

For this activity I gather the labeled male and female pelvic girdles and a number of unlabeled X-rays of pelvic girdles and place them together for the students to examine. If you have good representative bones in your collection, you could include one labeled, "The one found in the case by Tom McCune." By including a list of some of the sexual characteristic of the pelvis, students can circle the features that they see.

Go to Activity 2 Handout

• Activity 3: Sex Determination from Skull Morphology

For this activity, you will need two adult skulls labled "male" and "female" for comparison. If you have purchased plastic skulls, they will most likely be male since the markings are more prominent; therefore, you may have to order a few female skulls. Assemble several practice skulls for the students to examine and one labeled, "The one found in the case by Tom McCune." Make sure it is the same sex as the pelvis. Students verify the sex of the skeleton by identifying specific features of the skull and circling the characteristics that match their observations. Encourage the students to examine many skulls during this acivity Determinations cannot be made easily by observing one skull.


Go to Activity 3 Handout

• Activity 4: Height Estimation

Another key question that the anthropologist tries to answer is, "What was the height of the individual?" The height is determined by measuring specific bones and comparing their length to chart measurements based on regression formulae. Because lab bones are usually commingled, students will not have exact information about age, sex, and race of the individual for precise determinations, but this activity will enlighten students about how height assessments are made. I do not discuss regression analysis since these are introductory-level students, but if your students are more advanced you may want to include that information in the discussion. Select a femur from the same sex skeleton as the pelvis and skull and have the students measure its length and calculate the estimated stature range. Students can also take estimated measurements of their own femurs for comparison. Try palpating and measuring from the greater trochanter to the lateral condyle of the femur.

Go to Activity 4 Handout

• Activity 5: Age Estimation

Only estimated ranges are possible in determining the age of a skeleton (Pickering and Bachman 1997). Have the students make age estimates in the 0-5, 18-23, 30-40, and 60+ year ranges. Clues are derived from the fusion of the epiphyses of long bones, closure of endocranial sutures, and ossification of the sutures. In preadult individuals, the epiphyses and diaphysis union will be incomplete. In old age, the cranial sutures are less distinct, and the mandible height and thickness diminish and begin to appear more infantile. Sample X-rays can be used to illustrate epiphyseal plates. Hinged bones that open may be used to demonstrate epiphyseal lines. Closure of ecto- and endocranial sutures provide additional clues. In the 0-5 year range, sutures will be open with fontanels between the cranial bones. The 18-23 year range skulls will have rough suture lines compared to the 60+ age range, which will begin to display fading of sutures. Try to have a fetal skull and representative adult skulls for students to examine. The jawbones and analysis of tooth eruption can be compared using the fetal and adult skulls.

If you have an abundance of natural skulls, try to exhibit one with diminished height and thickness of the mandible for the 60+ range. Evidence of aged skeletons is often determined by degenerative changes. Many vertebrae exhibit evidence of lipping and signs of porosity. You can also select scapulae with atrophic or translucent spots.


Set up some bones as examples and some to challenge the students, including one to accompany the case. Ask students to estimate the age of the bones and record observations that supports their analysis.

Go to Activity 5 Handout

• Activity 6: Analysis of Pathological and Physiological Changes

Ask the students to look for evidence of pathological and physiological changes in bones. If you have no pathologic bones in your collection, students can make observations of bones that are broken or that have been damaged during handling. X-rays showing fractures can also be used to supplement this activity. Students should list any observable signs of trauma or pathology. For example, in forensic pathology, a broken hyoid bone suggests strangulation. If there is a crack in the calvaria, did it occur as a result of a fall off the lab bench or is it evidence of a fatal blow? The cracks of a deadly blow will look like a cracked hard-boiled eggshell while that post-mortem fall from the lab bench will yield a linear line. Create a display of three or four bones exhibiting some of these pathologic examples. Add one to complete the case and challenge students to find others in their bone boxes.


Go to Activity 6 Handout

Follow-up Exam Questions

To reinforce the value of this type of investigative activity and reward the students' efforts, I include practical exam questions that require analytical judgement. Some of my favorites are:

• These bones were found at a burial site. Are they most likely from one or more than one individual? [Students evaluate five or six bones including two from the same side of the body.]
• These X-rays were from a patient Pat Smith. Was Pat male or female? [Students analyze the X-rays of the pelvic bones, make a determination, and support their answers by describing two features using anatomical names and descriptions.]

CLASSROOM MANAGEMENT

The study of bones requires several lab sessions and outside class time. Students usually have some prior knowledge of the skeletal system before they begin this lab. I try to start with an orientation that builds on this prior knowledge. The first two orientation activities described below are done before the case is distributed. The class needs to be divided into groups of four to complete these avtivities.

• As an introduction to the bone case, students review the names of the bones and the relationship of the disarticulated bones to the articulated skeleton. An exercise that I have used for elementary students that complements the case involves having one of the students in each group lie down on a large sheet of paper. The other group members trace an outline of the body. The outline is used in arranging the disarticulated bones as they are examined. I encourage students to attempt this activity first without referring to their text or the articulated skeleton. After they have placed each bone, they are asked to compare their arrangements with the articulated skeleton and rearrange any bones they have misplaced. This activity takes approximately 15 minutes depending on the prior knowledge of the students.
• As an orientation to the bony landmarks, begin with the appendicular skeleton and have students each select a different bone and observe it for as many landmarks (bumps and holes) as they can find. Next, have the students draw what they see on 5" by 7" index cards and create names for all of their findings. The students are not allowed to use their textbooks but should rely on their imaginations instead. Ask some of the students to share a few of their names with the entire class. Question if students have identified any markings that they found difficult to describe and ask if they could use some help. At this point, I distribute a sheet of the anatomical names of the bony landmarks and ask students to see if they can find places where they could substitute some of the anatomical names. Afterward, I encourage students to look up the actual names of the markings and write them on the cards as well. The questioning strategies here are to help the students see commonalities among the anatomical names of the markings. Allow about 15 minutes for this activity.

These two orientation activities replace the customary instructor-focused pre-laboratory lecture spent pointing out and naming individual bones for students.

If you have a three-hour lab, the case can be distributed at this point. Have labeling tape available along with sets of disarticulated bones. Have the groups read the case and the first activity and begin identifying the landmarks of each bone. You will want to check their labeling to ensure that landmarks are correctly identified. The groups should also record a description that will help reinforce what they know about each bone. If your lab is two hours long, or students have had limited exposure to the skeletal system, you may want to give them the rest of the lab period to study and explore on their own. By beginning some of the labeling during the first lab, the groups can review the bones with each other prior to the second lab and be assured that they are studying the correct locations of the markings.

After working through the activities that lead up to the case, students are encouraged to work on the case as they study the bones. The motivation that I provide is a 10-point bonus toward their bone exam. I award five points for the bony landmark analysis activity and one point for each of the other activties described above. The case is turned in just before the bone exam.

REFERENCES

Acknowledgements: Publication of this case study on the website of the National Center for Case Study Teaching in Science was made possible with support from The Pew Charitable Trusts .