Forensic Anthropology and Ancestry Identification from Skeletal Remains

Introduction to Forensic Anthropology

Forensic anthropology is a relatively new field within anthropology. When it was first recognized as a forensic science about thirty years ago, there were only six forensic anthropologists, all of whom knew each other (Guntzel, 2004). The role of forensic anthropology in police work is to give investigators specific information about an unknown individual that they can use to assist with identification. When investigators have such information as age, sex, height, and ancestry, they can compare it to records of known missing persons and perhaps identify the body (Byers, 2001).

One such forensic anthropologist is Clyde Snow, who has worked both on individual cases and on scenes of political massacres around the world, including Guatemala, El Salvador, Argentina, Iraq, Zaire, Ethiopia, Zimbabwe, and Yugoslavia (Guntzel, 2004). He has also gathered forensic evidence from victims of serial killers such as the Green River Killer and Jeffrey Dahmer, as well as from man-made and natural disasters including the Oklahoma City bombing (Guntzel, 2004). Other cases he worked on include identifying the remains of Butch Cassidy and the Sundance Kid, and bones found at the site of the Battle of Little Bighorn, where Custer and Union soldiers were defeated in battle with Native Americans.

Another forensic anthropologist, Norm Sauer, received a call from the Michigan State Police reporting that they had found a body in some woods. There was no identifying information, and visual inspection could determine neither race nor sex. He evaluated the entire skeleton but focused on the pelvis and skull. The pelvis confirmed the sex, and he also took measurements of the distance between the eye orbits and the length and breadth of the skull. After performing calculations, he told the state police that the remains were those of a Black female. He estimated her height at between 5'2" and 5'6" and placed her age between 18 and 23 years. He also determined that she had been dead for more than six weeks but less than six months. Investigators compared this information to known missing-person cases and found a match from the area: a Black woman, 5'3" tall, and 19 years old (Shreeve, 1994).

While history may be enriched by investigations into sites such as Little Bighorn, the most immediately useful work of forensic anthropology is identifying the remains of unknown individuals to assist police investigations. Of all the information generated by Sauer's work, the most difficult to establish was the race, or ancestry, of the unknown woman. Nevertheless, that information was crucial to determining who the missing woman might be.

One obvious difficulty is that opinions abound on what race actually is. It is a complicated topic, in part because in our not-so-distant past, race was used to justify vile actions by one group against another. For forensic anthropologists to attempt to identify race based on an individual's skeletal remains, however, race in some form must exist in a physical sense. While many people might wish to erase the notion of race from our culture, as demonstrated by Sauer's example above, determining whether a person is of European, Asian, or African ancestry can be an important clue for police investigators.

Nevertheless, the issue of race is so complicated that our own government has struggled to define what it means by "race." The Office of Management and Budget, which oversees the decennial census, wrestled with racial categories throughout the 1990s. The categories originally planned for the 2000 Census included White, Black, American Indian (often called Native American), Eskimo and Aleut (also Native American), Asian or Pacific Islander, and "other." Noticeably absent were Hispanic and any category for those who consider themselves multicultural. The difficulties with labels based on ancestry mirror the difficulties faced by forensic anthropologists when they analyze skeletal remains.

There are essentially two schools of thought on this issue within anthropology. First, there are those who feel that only individual traits should be considered and who resist any temptation to cluster people by physical characteristics such as skin color or nose structure. Those anthropologists prefer the term "cultural affiliation" over "race." Other researchers recognize that the groupings some call "race" exist, have commonalities, and that those commonalities reflect biological fact. They prefer the term "race" to describe such groups (Byers, 2001).

What Is Race?

All agree that all human beings belong to the same biological species, Homo sapiens, meaning that all are capable of reproducing without barriers. In reality, however, people tend to choose reproductive partners from among those known to them. As a result, in some areas, people with similar physical characteristics cluster together. Over time, geographic areas can develop distinct trait frequencies even when the people who live there appear to share common ancestry. The issue of race also carries important cultural and moral weight. In the past, human variation divided into "races" was treated as a given, with each race considered distinct from others (Shreeve, 1994). Although anthropologists as a group did not support using these differences to rank people, the framework assisted those who wished to assert racial superiority, demand racial segregation, and commit social abominations in the name of racial purity. As Shreeve (1994) notes:

"Asians are typically supposed to have 'yellow' skin, wide flat cheekbones, epicanthic folds (those little webs of skin over the corners of the eyes), straight black hair, sparse body hair, and 'shovel-shaped' incisor teeth, to name just a few such distinctive traits. And sure enough, if you were to walk down a street in Beijing, stopping every once in a while to peer into people's mouths, you would find a high frequency of these features. But try the same test in Manila, Tehran, or Irkutsk — all cities in Asia — and your Asian bushel basket begins to fall apart."

One solution is to increase the number of categories and sort people into groups in a more refined way. For instance, one could subdivide the "Asian" group multiple times, but it still would not serve the purpose well. While most Asians have epicanthic folds, so do the Khoisan of southern Africa. Shovel-shaped incisors — a slightly concave back surface — are present in many Native American and Asian teeth, but the trait is also very common in Sweden (Shreeve, 1994).

A more neutral term that can serve the needs of forensic anthropologists is "ancestry." Forensic anthropologists work closely with law enforcement, and the physical appearance of a deceased person can greatly assist in determining who that person was. Their ancestry is an important piece of information under these circumstances, one that transcends the need for cultural sensitivity while recognizing that superficial appearance tells us nothing about a person's character. For practical reasons, this paper will follow the textbook convention and refer to those whose ancestors originated in the Orient as Asian; use "Native American" in place of "American Indian"; and define "Hispanic" as people whose ancestry is a mix of European and Native American. Forensic anthropologists must also recognize that people cross ancestry lines regularly when choosing reproductive partners, and that many people possess ancestry representing more than one group (Byers, 2001).

This reality makes the task of the forensic anthropologist difficult when it comes to determining race. Shreeve (1994) makes the point that while ancestry groups vary, there is more variability within each group than between groups. Dog breeders work hard to pair males and females in order to produce offspring conforming to rigid breed standards. Those breeds might be compared to the concept of race, but the truth is that the great majority of humans do not value conformity to arbitrary physical standards based on ancestry, and human physical traits vary significantly.

Certain practicalities exist when identifying the ancestry of skeletal remains. Because many remains will reflect the fact that many people have more than one ancestry in their family tree, the person should be assigned a minority ancestry if one is present. This is because, as a practical matter, this is how such individuals were most likely classified by their contemporaries in society (Byers, 2001). Since the goal is to help law enforcement identify the remains of an unknown person, societal factors must be taken into consideration.

As forensic anthropologists assess the physical characteristics that help them evaluate ancestry, it is important to keep in mind that these characteristics are only reliable for adults and not for children who have not yet reached sexual maturity (Byers, 2001). The one exception is the formation of teeth.

In the United States, the Census provides information regarding the ancestry of the population. According to the 1990 census, approximately 71% of the population was White and non-Hispanic; 13% was Black; 9% Hispanic; about 3% Asian; and slightly less than 1% Native American. About 4% were classified as "other" (Byers, 2001) — a significant figure for forensic anthropologists, as it illustrates how difficult the task can be when 4% of the population claims no specific ancestry. This suggests their skulls might not follow any clear ancestral pattern.

Very often, the identification of the characteristics discussed below is performed visually, which makes them somewhat subjective. Many traits cannot be easily defined in terms of measurement. For instance, the nasal bridge is frequently used as an important factor in determining ancestry because it varies by group. However, using this trait dependably requires that the anthropologist be precise about where the nasal bridge begins and ends (Byers, 2001). Despite best efforts at precision, all these features exist on a continuum. It may be difficult to determine whether a given bridge most closely reflects White, Black, or Asian characteristics.

Forensic anthropologists have established specific ways to measure the bone structure of the skull to identify ancestry. They examine nose structure, specific shapes of the face, the cranial vault, and the jaws and teeth. For the nose, they look at the root, bridge, border, spine, and width. Facial features of interest include the profile, shape, eye orbits, and lower eye border. On the cranial vault, the browridges, muscle marks, vault sutures, and postbregma are evaluated. Finally, they examine the lower jaw, palatal shape, and upper incisors (Byers, 2001).

These features are assessed as precisely as possible using specialized tools. The anthropometer measures the long bones of the leg. A sliding caliper takes various measurements on the skull. A Boley gauge measures teeth. A spreading caliper measures head length and width, and a tape measure records the diameter of the head (Guntzel, 2004). The need for such measurements is illustrated by the case of a doctor who found a skull on a Native American reservation. He concluded it was Native American, unduly influenced by where the skull was found. Careful analysis showed that the skull actually belonged to a person of European ancestry (Byers, 2001).

The nose is the most useful facial feature in determining ancestral group, because it has five specific characteristics that tend to vary fairly clearly among the three ancestral groups. The root is the spot where the nasals meet the frontal bones. Sometimes it projects outward from the facial plane, while other times it is quite flat — so flat that when viewing the skull from the side, an observer can see both eye orbits (Byers, 2001).

Basics of Ancestry Identification

The bridge is a bony ridge formed by the nasals. Typically this ridge is high in Whites and resembles an A-frame house. By comparison, the bridge of a typical Black person resembles a Quonset hut, and in those of Asian ancestry it looks more like a "sagging tent" (Byers, 2001).

The nasal spine, when present, appears as if it were pinched into a pointy protrusion. In Whites it is often pronounced, but it is smaller in people of Asian ancestry and almost entirely absent in Blacks (Byers, 2001).

The lower border of the nose may be flat or raised significantly, depending on ancestry (Byers, 2001). The width of the nasal opening also varies significantly across ancestral groups. In Whites it tends to be narrow and shaped somewhat like an isosceles triangle. In Blacks it is more like an equilateral triangle. In Asians, the nasal opening does not aid in identification (Byers, 2001). The table below summarizes these characteristics.

Primary Distinguishing Features

Nasal Structure by Ancestry (Byers, 2001)

Root — Whites: high, narrow; Blacks: low, rounded; Asians: low, ridged
Bridge — Whites: high; Blacks: low; Asians: low
Lower border — Whites: sharp; Blacks: —; Asians: flat, sharp
Spine — Whites: pronounced; Blacks: small; Asians: small
Width — Whites: narrow; Blacks: wide; Asians: medium

The face is also useful, especially in profile, because it reveals the structure of the lower jaw. Blacks have larger jaws than Whites and Asians, and the jaw tends to protrude more in profile. By comparison, the face of Whites tends to be flatter, or may even show a receding jaw, whereas in Asians the degree of projection falls between the other two groups. The shape of the face also varies; Blacks and Whites tend to have narrower faces than Asians (Byers, 2001). Eye orbits differ as well: Whites tend to have angular eye orbits, while those of Asians tend to be round and those of Blacks somewhat rectangular (Byers, 2001). Finally, looking at the lower eye border in profile, it tends to push forward in Asians but not in Whites or Blacks (Byers, 2001).

Facial Structure by Ancestry (Byers, 2001)

Profile — Whites: straight; Blacks: projecting; Asians: intermediate
Shape — Whites: narrow; Blacks: narrow; Asians: wide
Eye orbits — Whites: angular; Blacks: rectangular; Asians: rounded
Lower eye border — Whites: receding; Blacks: receding; Asians: projecting

Evaluation of the cranial vault includes the browridges, muscle marks, vault sutures, and postbregma. Whites tend to have both the most pronounced browridges and the most pronounced muscle marks (Byers, 2001).

The vault sutures of Asians are distinct, with significantly zigzagged edges, while the sutures in Whites and Blacks do not show such extreme undulations (Byers, 2001). Additionally, at the cranial suture known as the bregma, Black skulls are typically slightly concave, where in Whites and Asians the same spot — easily observed in profile — will be flat or slightly convex (Byers, 2001).

Cranial Vault Structure by Ancestry (Byers, 2001)

Browridges — Whites: heavy; Blacks: small; Asians: small
Muscle marks — Whites: rugged; Blacks: smooth; Asians: smooth
Vault sutures — Whites: simple; Blacks: simple; Asians: complex
Postbregma — Whites: straight; Blacks: depressed; Asians: straight

The jaws and teeth can also be useful in determining ancestry. Those of White ancestry often have crowded teeth due to insufficient jaw space, a problem uncommon among both Blacks and Asians because they have larger jaws. This is particularly marked in Blacks, whose lower jaw is large enough to allow room for a tooth behind the third molar (Byers, 2001). In addition, the dental arch varies by ancestry. The dental arch in Whites is parabolic, or more pronounced, compared to Blacks, where it is hyperbolic, or less pronounced. In Asians it is flatter still, more rounded than arched (Byers, 2001). The teeth of Asians, particularly the incisors, have a specific shape sometimes called "shoveling" — they are scooped out on the anterior side. This trait occurs in about 90% of Asians, including Native Americans, but also in slightly less than 15% of Blacks and Whites (Byers, 2001), demonstrating that all of these traits have significant limitations.

Jaw and Teeth Structure by Ancestry (Byers, 2001)

Palatal shape — Whites: small; Blacks: large; Asians: large
Upper incisors — Whites: spatulate; Blacks: spatulate; Asians: shoveled

While the indicators discussed so far are both somewhat imprecise and not entirely consistent within ancestry groups, using the post-cranial skeleton for ancestral identification is even more problematic. Although some bones have been studied, others have not, and even where bones such as the pelvis have been evaluated, whole groups of people have been omitted (Byers, 2001), making the post-cranial bones of limited use.

Some differences can be identified, however. For instance, the femur, or thighbone, typically curves somewhat. Blacks and some Native Americans from South America, however, have relatively straight femurs (Byers, 2001). Other structural differences exist as well, including the shape of the head and neck of the femur. In Blacks, the head and neck tend to lie horizontal when the bone is placed with its posterior side down. Among Whites, the head and neck are angled when placed in the same position (Byers, 2001).

In addition, Blacks tend to have lighter bones with lighter muscle markings. The bones tend to be more slender than those of Whites, and the pelvis tends to be higher and less wide (Byers, 2001). However, these traits alone do not definitively distinguish the two groups.