Two of the most commonly used methods in forensic anthropology are the metric (anthropometry) and morphological (anthroposcopy) assessment of the characteristics of living and skeletal remains. The origins of these methods go back to the eighteenth century, when there was a great deal of interest in human diversity, especially of those who had just been ‘discovered’ by the colonizing European nations.
In the following century the methods were further developed for the purpose of tracing the ethnic origins of human populations. In the first half of the twentieth century, these methods (especially anthropometry) played an important role in understanding human variation and evolution. In the second half of the century, as the concept of race fell from the research paradigm of anthropology, anthropometry and anthroposcopy took on a new role, especially in the fields of human engineering and forensic anthropology.
In essence, anthropometry is a systematic study of human measurements. Dimensions taken are internationally agreed and standardized linear and angular measurements. If the dimensions are taken from a particular region of the human body, the technique may have a different name, such as cephalometry for the head, craniometry for the skull, odontometry for the teeth and osteometry for the skeletal system. There are many different data collection forms that list measurements to be taken from a living person and from a skeleton (skull and the postcranial skeleton, respectively). To these may be added others to suit the research interests of the investigator. The measurements now form the very foundation of the methodology used to study human growth, differences between populations, and health and disease-related problems.
Anthroposcopy is more complex and requires years of experience in assessing the variation of a feature in different populations. The assessment criteria used in this technique are also at the very root of anthropometry; that is, anything that has a morphological variation can be observed with the naked eye and can also be measured. Many anthropologists therefore rely heavily on first-hand observation of how large or small, short or long, rough or smooth, robust or gracile are the features being examined. Yet many observable characteristics cannot easily be quantified. These features should be recorded, as such, without any quantification. There are also blank forms for recording those anthroposcopic features that have traditionally been observed in both the living person and the skeleton. To these one must add many observable features of dentition.
Photographic comparison has provided lists of anthropometric landmarks and dimensions that can be modified for use in comparing two different facial images. The same approach can be applied to estimate the age of a living person from a photograph. This is commonly done if the picture or an Internet-based graphic file is thought to be that of a naked child. In this case, secondary sexual characteristics, such as breast development and axillary and pubic hair in a girl, and facial hair in a boy, may have to be assessed morphologically rather than metrically.
These metric and morphological characteristics can be assessed in both the living and in skeletons. Their use, however, is more common in skeletal remains. This article reviews the use of anthropometric and anthroposcopic characteristics in the study of the forensic anthropology of skeletal remains.
Anthropometric Analysis of Skeletal Remains
Forensic anthropology has benefited considerably from both anthropometric and anthroposcopic techniques. Many biological differences in terms of sex, race and stature depend largely upon human size and shape. To assess population variation, a set of measurements can be obtained from skeletal collections of known demographic characteristics. Studies have indicated that determination of sex or other demographic characteristics require population-specific studies. A sample of 50 or more individuals per subgroup (e.g. 50 males of a black sample) may fulfill the minimum requirements of the study, assuming that there are that many skeletons in the collection. Table 1 lists descriptive statistics of osteometric dimensions in males and females of different populations from dissection room collections in South Africa (Negroid and Caucasoid) and Japan (Mongoloid). The dimensions are from both the skull, including the mandible, and the long bones of the postcranial skeleton. The differences between the samples can be analyzed using Student’s Mtest or even analysis of variance statistics. Many dimensions show similarity between, for example, the Japanese and Whites, or between Whites and Blacks. It is clear that size plays an important role in population difference; however, most anthropometric analysis involves multiple dimensions. Anthropologists have relied heavily on this factor in determining sex and race and estimating stature. Anthropometric dimensions, as such, assume that any two or more groups can be analyzed in terms of their body size.
Sometimes differences in size between individuals, such as a male and a female, or populations may have to be assessed in terms of shape. Shape generally falls into anthroposcopic determination. For example, cranial (and cephalic) shapes alone can separate one group from another. Although this observation can be made with a naked eye, it is easier if the observation can be quantified. A traditional solution to assessing shape using anthropometry has been the creation of an index with two dimensions describing the structure. Therefore an index is the percent expression of the ratio (proportion) of a smaller dimension over a larger one; for example, the cranial index, which is calculated as 100 * cranial breadth/ cranial length. Table 2 lists several commonly used cranial indices for the same populations shown in Table 1. The advantage of an index is severalfold. It eliminates the size difference between individuals; that is, a tall person can be compared with a short one. Elimination of size difference also provides suggestions about the shape (morphology) of a structure. For example, a cranial index of 70.9 in Blacks describes the shape of that person as dolichocranic or longer skull (dolichocephalic if the dimensions are taken from a living person). The same index describes a Japanese skull as mesocranic, that is, rounder. Gnathic index is formed by the ratio of the basion-prosthion length divided by the basion-nasion length. The purpose of the index is to show which population has the most protruding chin. It is clear that Blacks have the largest value. The following is an example of how the cranial index has been classified:
|Cranial length (or length-breadth) index||Range|
Many indices exist and others can be created if the investigator deems it necessary. However, for population comparative purposes, only those that are used worldwide are reported in a study. It also reduces interobserver errors, unlike anthroposcopic assessment, which depends on the observer’s knowledge of the population.
Because anthropometry deals with body dimensions, statistics play an important role: in fact, many earlier statistical techniques were developed using anthropometric dimensions. Statistical techniques that are commonly employed in forensic anthro-pometric studies include discriminant function and regression analyses.
Table 1 Comparative osteometric dimensions in Japanese, Whites, and Blacks8
|Minimum frontal breadth||46||95.3||5.2||53||97.4||4.1||45||97.1||4.0|
|Minimum ramus breadth||44||32.3||3.4||46||31.3||3.5||45||35.4||3.3|
|Humeral head diameter||44||44.1||1.8||55||49.0||3.2||43||43.7||2.2|
|Humeral epicondylar breadth||44||59.8||2.3||55||64.3||3.9||43||61.5||6.0|
|Femoral maximum length||44||417.4||16.5||56||469.7||28.0||43||463.6||21.8|
|Femoral head diameter||45||46.0||2.0||56||48.5||2.7||42||45.5||2.3|
|Femoral midshaft circumference||45||85.4||4.6||56||93.2||6.1||44||89.7||5.6|
|Femoral distal breadth||42||80.7||3.1||56||84.6||4.6||43||79.5||4.1|
|Tibial proximal breadth||45||73.4||2.8||56||79.1||4.9||44||75.1||3.6|
|Tibial distal breadth||46||45.4||2.4||45||46.9||2.6||43||46.4||7.4|
|Tibial circumference at nutrient foramen||46||91.9||5.0||56||98.0||6.6||40||97.8||6.9|
|Minimum frontal breadth||35||91.3||5.2||53||93.5||4.5||45||93.4||4.4|
Table 1 Continued
|Minimum ramus breadth||29||31.3||3.2||49||28.6||2.7||45||32.9||3.1|
|Humeral head diameter||35||39.1||2.6||49||43.1||2.5||45||37.7||2.1|
|Humeral epicondylar breadth||35||52.1||3.8||48||55.9||2.8||45||53.4||3.6|
|Femoral maximum length||34||390.3||23.7||50||437.6||20.7||45||423.7||22.3|
|Femoral head diameter||34||40.7||2.5||50||43.0||2.4||44||39.2||2.6|
|Femoral midshaft circumference||34||78.1||6.3||49||84.7||5.5||45||78.8||4.7|
|Femoral distal breadth||34||72.2||4.3||49||75.1||3.3||45||69.5||4.8|
|Tibial proximal breadth||34||65.8||4.7||50||69.8||3.7||45||64.9||7.3|
|Tibial distal breadth||34||40.5||2.6||48||42.0||2.5||45||39.8||2.2|
|Tibial circumference at nutrient foremen||34||82.4||8.3||50||87.5||6.0||45||84.9||5.3|
Table 2 Comparative osteometric indices in Japanese, Whites, and Blacks
Anthroposcopic Analysis of Skeletal Remains
Anthroposcopic (or morphological) analysis has contributed considerably to the study of forensic anthropology. Comparison of photographic images with those of videotape can best be done by examining all facial features for morphological variation; published studies include tables of those features that play a role in assessing the similarities and differences between the images from a photograph and video recording. In osteological studies, morphological assessment of the skull and pelvis are the best known. Many forensic anthropologists rely on variation in, for example, the shape of the mastoid process or subpubic angle, as much as, if not more than, the metric features of these structures. As a matter of fact, anthroposcopic characteristics may go beyond population boundaries; for example, the subpubic angle is a better structure for determining sex than measurement of the entire pelvis.
There are two considerations in morphological analysis. A structure can be viewed as large or small with a scale in between. In some ways, this is similar to anthropometry because it can be measured with a numeric scale. Therefore, using the above example, the subpubic angle can be very wide or U-shaped or very narrow and V-shaped. The same applies to the size of the mastoid process. In this case anthropometry and anthroposcopy assess the same anatomic features. A morphological feature can also be non-metric or discrete (not measurable). There are hundreds of such features in the human skeleton. Some of these include intersutural or wormian bones. For example, the inca bone is a structure formed where the sagittal suture meets the lambdoid suture and is not present in every individual. The third trochanter of the femur is rarely seen in a skeleton These two are examples of features that are often assessed as ‘present’ or ‘absent’ when a skeleton is examined. Because of this simplicity, some anthropologists have thought such features might aid the study of genetics in skeletal remains.
There are also morphological features that are not as simple as these nonmetric traits but assessment of which may depend on shape alone. For example, accessory articular facets on the ilium and the corresponding side on the sacrum are morphological features and provide considerable information about an individual’s lifestyle, even though they are rarely measured linearly or otherwise.
Anthropometry and anthroposcopy have been the most important research tools in biological and forensic anthropology. These two methods of observation and data collection can be made both on the living and on skeletonized human remains. As research tools, they have contributed to the analysis of human variation in terms of race, sex and body dimensions, such as stature. These areas of research have explained those dimensions and morphological features that describe sexual dimorphism, and the differences between sexes that may have been caused by social and physical environmental factors or simply by evolutionary mechanisms, such as selection. Many growth studies of the musculoskeletal system have been based on anthropometry of children. Predictions can be made from such studies; for example, to determine whether a child has the chromosomal mutation that will cause the Down syndrome, or what the predicted height will be at a given age.
Forensic anthropological anthropometric (and osteometric) dimensions have been used to develop many discriminant function formulae to determine sex and race from the skeleton. They are also used to estimate stature from long bones. These and other uses assist the police in identifying both the unknown victim and the culprit who may have committed the crime. The same dimensions in the study of a video recording of a crime scene, facial size and proportions of facial features can be estimated: for example, the length of a person’s nose can be estimated from a video image and a photograph. Some anthropologists even attempt to estimate stature and the proportions of one part of the body to another in video surveillance images recorded during the commission of a crime.
Morphological analysis of unmeasurable features usually falls into the area of anthroposcopy. These features are assessed qualitatively (without using any measuring device) by an experienced person. While some anthropologists use models to compare morphological features, experience is extremely important because of the geographic diversity of the human species and resulting differences between them. Its use in forensic anthropology is mainly seen in the analysis of the skeletal remains rather than living individuals. An exception to this may be the evaluation of facial images in a photograph and video tapes. To these one may add the study of growth-related changes in the human body, especially when there is the question of age estimation from the picture of a person who was thought to be a child. Morphological assessment of osteological remains are important areas of observation in forensic osteology. It provides not only features of sex and race but also shows variation in the human skeleton that may be explained in terms of asymmetry, pathology or anomaly. Each of these features may provide information about age, pathology and trauma, time since death, effects of animals on the skeleton, and information as to whether a particular feature was caused ante mortem, peri-mortem or post mortem.