Attribution of Ancestry Activity

Patterns of geographic variation of the human skeleton are used to identify the probable race or ancestry of an individual. Most forensic anthropologists use a three-ancestry model that includes Asian, Black/African, and Caucasoid races. Native Americans are typically included in the Asian race.

Compared to sex, age, and stature estimation, race or ancestry determination is not absolute, because race itself is not clear-cut. While variation in physical and genetic traits forms broad patterns among humans, some characteristics may be emphasized more than others, depending on the culture doing the classification. In addition, race determination is “more difficult, less precise, and less reliable” because “no human skeletal markers … correspond perfectly to geographic origin” (White 1991:328-329). Often, a skeleton exhibits characteristics of more than one racial group and does not fit neatly into the three- ancestry model. And, finally, in forensic analysis, many skeletal indicators used to estimate race are non-
metric traits, whose documentation through anthroposcopic methods can be somewhat subjective, varying from researcher to researcher.
Yet, given these problems, ancestry estimation is a critical endeavor in forensic identification, as sex, age, and stature vary considerably depending on the race of the individual. Indeed, knowing the sex of the subject is crucial to making an accurate assessment of ancestry because some of the features that may be attributed to one ancestral group may be characteristic of one sex or the other.

Skeletal indicators of race focus primarily on skull and dental traits. Ancestry indicators on the skull are both non-metric and metric traits and include robusticity, lengths and widths of skull features, shapes of skull features, and unique population-specific dental features.

For the assignment outlined below, we will explore a selection of these measurements, as introduced and discussed in your text (Byers, 2011).

Note: This is not a timed exercise and you can use your book or other materials to assist you. The assessment is due September 27 (at 11:59pm CT). Submit the completed assessment in the Ancestry Assessment Dropbox.

Assignment: Determination of Ancestry or Racial Affiliation

Compare the skulls (and/or measurements) in the activities below to the known skulls and figures in the reference materials. Part 1 involves metric traits; Part 2 involves non-metric traits. Using the “three-race model”, determine the most likely racial affiliation for each specimen.
All measurements should be recorded in mm.

Important note:

You may find that some remains exhibit characteristics that can be attributed to two groups. In these cases, assign the ancestry to the group that is considered the minority in the geographical area, as this is how the person would be perceived in life. Thus, if the skeleton exhibits part White and part Black features in a predominantly White area, place it in the Black category. Ancestry is attributable only to adults, as a majority of characteristics that help assess this trait are only found in adult remains.

Part I. Metric Traits – Cranial measurements

The three ancestral groups are separated here by applying discriminant function analysis to the measurements of the skull. We will measure two skulls: one female, and one male.

Measurement Description
BaPr Basion to prosthion
ML Maximum length: from the glabella to the occipital bone (measuring the greatest distance)
MB Maximum Breadth: from highest points on squamosal suture (measuring the greatest
distance)
BaBr Basion to bregma
BaNa Basion to nasion
BB Bi-zygomatic breadth: perpendicular to the sagittal plane
PrNa Prosthion to nasion
NB Nasal breadth: measurement within the nasal cavity (measuring the widest distance)

Figure 1 Female Cranium (Anterior View)

Cranium 1 – Female

Step 1: Using the Discriminant Functions table above, calculate the values for Whites versus Blacks in
Table 1a and enter the results in the appropriate box.

Step 2: Using the Discriminant Functions table above, calculate the values for Whites versus Native Americans (Asians) in Table 1b and enter the results in the appropriate box.

Step 3: After calculating the discriminant function values, select (using highlight tool) the probable race at the bottom of each table by determining whether the total is greater or lesser than the stated value (in red).
Table 1a
Measurement Value Coefficient Calculation
BaPr 80 X 1.74 =
ML 168 X 1.28 =
MB 136 X -1.18 =
BaBr 127 X -0.14 =
BaNa 88 X -2.34 =
BB 118 X 0.38 =
PrNa 58 X -0.01 =
Nb 19 X 2.45 =
Total

White < 92.20 < Black

Table 1b
Measurement Value Coefficient Calculation
BaPr 80 X 3.05 =
ML 168 X -1.04 =
MB 136 X -5.41 =
BaBr 127 X 4.29 =
BaNa 88 X -4.02 =
BB 118 X 5.62 =
PrNa 58 X -1.00 =
Nb 19 X -2.19 =
Total

White < 130.10 < Asian

Step 4: Go to Table 1c and highlight the appropriate row in the Function Results column (e.g. if the results of both discriminant functions indicate White, then highlight the White-White row) and enter the results in the box below Table 1c.

Note: If the discriminant fuction results indicate Black-Asian, you must perform an extra step.

Step 5: At the bottom of Table 1c, enter the White-Black function total above W-B Total. Now place the White-Asian function total above W-A Total. Then, multiply the W-A Total by the cofficient (0.709) and place the result in the preceding space. Compare the two values – if the W-B Total is greater than the W-A multiplication result, then the individual is Black (highlight the “>” sign); if the W-B Total is less than
the W-A calculation, then the individual is Asian (highlight the “<” sign). Use highlight tool to select Group.

Enter your final assessment in the space below Table 1c.

Table 1c
Function Results Ancestral Group
White-White White
White-Asian Asian
Black-White Black
Black-Asian < Asian > =0.709 *

Black
W-B Total W-A Total

Cranium 1 Results:

Cranium 2 – Male

For this section, in Step 1, examine the male cranium photographs (below) for the relevant measurements instead of using a table of values as your primary data, as you did above. Then, follow the same procedure as for the female cranium, this time, entering the values in the appropriate columns in the tables 2a, 2b and 2c, below.

135

142

30

Figure 2 Anterior View

Figure 3 Lateral (Left) View

Table 2a
Measurement Value Coefficient Calculation
BaPr X 3.06 =
ML X 1.60 =
MB X -1.90 =
BaBr X -1.79 =
BaNa X -4.41 =
BB X -0.10 =
PrNa X 2.59 =
Nb X 10.56 =
Total

White < 62.89 < Black

Table 2b
Measurement Value Coefficient Calculation
BaPr X 0.10 =
ML X -0.25 =
MB X -1.56 =
BaBr X 0.73 =
BaNa X -0.29 =
BB X 1.75 =
PrNa X -0.16 =
Nb X -0.88 =
Total

White < 22.28 < Asian

Table 2c
Function Results Ancestral Group
White-White White
White-Asian Asian
Black-White Black
Black-Asian < Asian > =3.99*

Black
W-B Total W-A Total

Cranium 2 Results:

Part II. Non-Metric Traits

Anthroposcopy, or the study of non-metric traits, is also used in attributing ancestry. In this part, you will be looking at several different characteristics of a skull to estimate ancestral affiliation.

On the answer sheet, use the highlight function to highlight all the skull characteristics that you observe on Cranium 3 (below) and make a final count at the end. Then identify racial affinity (and explain why) in the space following Table 3.

Note: If a specimen has a significant number of traits of more than one race, select the “Minority” race.

Zoom in the document (in Word: select the View tab, then Zoom) if you want a closer look at a particular feature.

Refer to the charactersitics in the Actvity Reference Materials and your textbook for help.

Figure 4 Inferior View

Figure 5 Anterior View

Figure 6 Lateral (Right) View

Figure 7 Posterior View

Figure 8 Superior View

Table 3
Feature White Black Asian
Nose
Root High, narrow Low, rounded Low, edged
Bridge High Low Low
Spine Pronounced Small Small
Lower Border Sharp (sill) Guttered Flat, sharp
Width Narrow Wide Intermediate
Face
Profile (alveolar prognathism) Straight Projecting Intermediate
Shape Narrow Narrow Wide
Inter-orbital breadth Narrow Wide Intermediate
Eye Orbits Angular Rectangular Rounded
Lower eye border Receding Receding Projecting
Vault
Browridges Heavy Small Small
Muscle marks Rugged Smooth Smooth
Vault sutures Simple Simple Complex
Post-bregma Straight Depressed Straight
Jaws and Teeth
Jaws Small Large Medium
Palatal shape Parabolic Hyperbolic Elliptical
Upper Incisors Spatulate Spatulate Shoveled
Other
Wormian Bones Absent Absent Present
Metopic suture (retained) Trace None None
Zygomaticomaxillary sutures S-shaped S-shaped Angled
Total count

Cranium 3 Results:

Part III. Final Assessment

Briefly write your conclusion (minimum 250 words) on the two methods used to attribute ancestry (metric vs.
non-metric). Which method did you think was more accurate? And why? What are some drawbacks? Offer examples.

REFERENCES

Byers, Steven (2011) Introduction to Forensic Anthropology (4th ed). Prentice Hall.

France, D. L. (2003) Lab Manual and Workbook for Physical Anthropology (5th ed.). West / Wadsworth.

White, T. D. (1991) Human Osteology. Academic Press.