FRS653 LAB 7 Bones - Lab report on analysis of skeletal remains PDF

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Lab report on analysis of skeletal remains...

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LABORATORY REPORT

SUBJECT: FORENSIC BIOLOGY COURSE CODE : FRS653 GROUP: AS2535A1 EXPERIMENT: EXPERIMENT 7 – ANALYSIS OF SKELETON REMAINS

EXPERIMENT 5: ANALYSIS OF SKELETON REMAINS

OBJECTIVES: Students will be evaluated as to whether or not they correctly identified the gender, age and race of the individual. In this activity, skeletons will be examined for how they vary according to the following: 

Gender

(based on the pelvis & skull)



Race

(based on the maxilla, and other characteristics of the skull)



Age

(based on general characteristics)



Height

(calculated based on the length of individual bones)

GENDER One of the issues of concern to the forensic anthropologist is the gender of the human remains. There are several ways to more accurately determine the gender of a skeleton. One of them is by examining the pelvic bone, which can be identified accurately 95% of the time.

Images from http://www.clipart.com, and adapted by Mr. Lazaroff

Original images from http://www.boneclones.com

Circle the Appropriate Answer Angle: > 90 degrees or < 90 degrees Angle: > 90 degrees or < 90 degrees Sacrum: Forward or Backward Sacrum: Forward or Backward Pelvic Outlet: Small or Large Pelvic Outlet: Small or Large Ilia: Close or Spread Ilia: Close or Spread Female or Male Female or Male

Another way is to examine the skull. This is still fairly accurate, but not as accurate as the pelvis. Forensic anthropologists can accurately identify the skull somewhere between 85% and 90% of the times. This can be complicated by

several factors. If a skull is incomplete, then, of course, there is less to work from. Some of the distinguishing characteristics, such as larger bone landmarks for muscle attachments in males, can be easily confused with the landmarks of more athletic females. To put it simply, since the landmarks are often for the attachment of muscles, the larger the muscles, or the more one uses the muscles, the larger the landmarks.

Landmarks Chin Mastoid Process (Behind Ear) External Occipital Protuberance (Back of Skull) General Anatomy Forehead

Vertical

Brow Ridges (Location of Eyebrows) Muscle Lines Orbital Margins (Edge of Eye Socket) Angle of Ascending Ramus (Back Corner of the Jaw)

Female Rounded

Male Square

Small

Large

Small (Not Prominent)

Large (Prominent)

Gracile (i.e., Graceful)

Robust Receding (Careful with the comments . . .)

Slightly Developed

Prominent

Slightly Developed

Prominent

Sharp

Rounded

Obtuse

Close to 90 degrees

Now try to identify the skulls below by gender:

Original images from http://www.boneclones.com Chin Mastoid Process

Occipital Protuberance General Anatomy Forehead Brow Ridges Muscle Lines Orbital Margin Angle of Ramus Gender

Circle the Appropriate Answer Rounded or Square Rounded or Square Small or Large Small or Large Small or Large

Small or Large

Gracile or Robust

Gracile or Robust

Vertical or Receding Slight or Prominent Slight or Prominent s Sharp or Rounded 90 degrees or Obtuse Female or Male

Vertical or Receding Slight or Prominent Slight or Prominent Sharp or Rounded 90 degrees or Obtuse Female or Male

Now that you have had some practice, what about this lone skull?

Circle the Appropriate Answer Chin Rounded or Square Mastoid Small or Process Large Occipital Small or Protuberance Large General Gracile or Anatomy Robust Forehead Vertical or Receding Brow Ridges Slight or Prominent Muscle Lines Slight or Prominent Orbital Margins Sharp or Rounded Angle of 90 degrees or Ramus Obtuse Gender

Female or Male

Original image from http://www.boneclones.com

RACE There are several features that can be used to determine the race of an individual. In terms of the skull, a great place to start is the maxillary bone. The left and right maxillary bones from the roof of the mouth, contain the upper 16 teeth in the adult (the upper 10 teeth in the child), and form the outline of the nasal cavity (the nasal cavity itself involves several other bones: ethmoid, inferior nasal conchae, lacrimal, nasal, sphenoid, and vomer).

The arch of the maxilla can be found in three basic shapes: hyperbolic, parabolic, and rounded. Each of the following three races has their own shape: (1) African = hyperbolic, (2) European = parabolic, (3) Asian = rounded.

Images from http://cseligman.com/text/history/ellipses.htm

The incisors, as well, differ in their basic shape. The incisors fall into two basic categories, based on the shape of the lingual (tongue) surface of the tooth. These two categories are: (1) shovel-shaped, and (2) spatulate, or spatula-shaped. As there is more than one race with spatulate incisors, other indicators are necessary to positively identify race, although this single feature can be used to eliminate one of the possibilities. Each of the the following three races have their own shape: (1) African = spatulate , (2) European = spatulate , and (3) Asian = shovel-shaped.

Based upon both criteria, label the following maxilla according to race:

Original image from http://www.boneclones.com

Arch Shape Incisor RACE

Circle the Appropriate Answer Hyperbola, Hyperbola, Parabola, Hyperbola, Parabola, Parabola, or or Rounded or Rounded Rounded Spatulate or Spatulate or ShovelSpatulate or Shovelshaped shaped Shovel-shaped African, Asian or African, Asian or African, Asian or Caucasian Caucasian Caucasian

In addition to determining gender, there are characteristics of the skull that can be used to determine the race of an individual. Many of these features are quite subtle, and require detailed examination of the skull. A couple of features, however, are more easily seen. For example, in people of African ancestry, the nasal opening is more flared. Another example is that of the zygomatic arch (or

cheek bone), which is angled more forward in people of Asian ancestry, thus giving the person a slightly more flattened face. Unfortunately, a true examination of racial characteristics is not possible on a worksheet. AGE The idea of age being represented by the skeleton was introduced in the Skeletons as Forensic Evidence website we looked

at earlier. One way we could tell

was by looking at the condition of the bones themselves, with the older bones being more likely to be arthritic. Examine the bones below, and label which is arthritic (and therefore older), and which is the younger:

Original image from http://www.boneclones.com

Arthritic Age

Circle the Appropriate Answer Yes or No Yes or No Younger or Older Younger or Older

Another way to determine age is by looking at the development of the sutures:

Images from http://www.clipart.com, and adapted by Mr. Lazaroff

Note, for example, that the adult skull has no remaining suture (called the frontal suture) in the middle of the Frontal bone. Remember, also, that all the sutures ultimately become more filled-in ("closed") as we age.

Compare the two

skulls below to determine which skull is from an adult, and which is from an adolescent:

Original images from http://www.boneclones.com

Circle the Appropriate Answer Frontal Suture Present or Absent Present or Absent Other Sutures "Open" or "Closed" "Open" or "Closed" Age Adolescent or Adult Adolescent or Adult

DISCUSSION: 1. What is the easiest way to determine the gender (using the skeleton) of an individual, and why? The easiest way is probably by examining the pelvic bone caused by obvious differences that can be detected between male pelvic bone and the female’s one.

2. What is the easiest way to tell (using the skeleton) whether a teenager is lying about her/his age, and why? By observing the condition of the bones, we can determine the age range of a person, where older people’s bones are more likely to be arthritic.

3. Why can determining gender from a skull be difficult? Determining gender from a skull can be difficult because comparison of the skull’s gender are mainly based on size, and sizing is very subjective. For example, a skull of an athletic female can be confused for a male because larger bone usually indicates to a male.

4. Why should a forensic anthropologist use more than one bone (if possible) to determine the height of an individual? One bone only is not sufficient to indicate the range of height of a person, other long bones are also required to determine the height.

5. What other issue is important to question four, especially if there is only one bone from which to work? If there is only one bone to work with, then the range of height determined will most likely not be accurate

CONCLUSION: To conclude, forensic anthropologist decided that to determine the gender of an individual, the observation of pelvic bone and skull must be done because there are physical differences between male’s and female’s bones. Besides, a person’s age can be determined by observing the condition of the bones, whether it is arthritic, which is older, or not. Finally, in order to determine the race of an individual, the arch of maxilla and shape of the lingual can be observed and compared....