Chapter 5: Processing and Examining Human Remains

SKELETAL PROCESSING AND PREPARATION

Osteological assessment of human remains forms an essential part of forensic work, especially during the examination of extensively decomposed, dismembered, or burnt bodies. However, if those bones are obscured by other materials the bones must be first processed before an analysis can be completed. ² Bone processing involves the removal of soft tissue and other adherent material.^1/2 This material may include debris from plants, dirt, and concrete. Before processing can begin the state in which the remains arrived to the lab must be documented, with photos and notes, and any non-osteological evidence, such as cloth, removed. A trauma analysis should be done both during this stage and once the bones are processed. This is necessary as certain indicators of when a fracture occurred could be removed through this process.²

There are different techniques or methods used in bone preparation which include insect consumption and cold or warm-water maceration. Boiling and subsequent mechanical cleaning of skeletal material is also used. Solutions of organic and inorganic chemicals have been used as well to remove soft tissue from bones. ¹ The state of preservation of the skeletal remains will dictate the optimum cleaning method but washing gently with tepid or cold water is the most commonly adopted approach.⁸

Maceration

Maceration involves soaking remains in either cold or warm water. Cold maceration involves placing the remains in room temperature water and sealing the container. This is less likely to damage the bones, but is a slow process. In warm maceration the remains are placed in water that sits just below boiling. This is a much faster process, however, there is higher potential that the bones will be damaged.² Standard maceration techniques requires between 2 days and 8 weeks depending on the amount of bacteria present, the size of material being macerated and the temperature of the environment during the maceration. Maceration techniques remove soft tissue by the destruction of biomolecules, but the applied techniques may also affect the morphology and the molecular integrity of the hard tissue itself. Meaning they may unwittingly eliminating valuable DNA evidence in the process.¹

The bones should not be immersed into deionized water to avoid dissolving the bone mineral, while the water should be changed regularly and soil remnants should be sieved to capture small bones or bone fragments. Bones should be left to dry naturally and not in direct sunlight. If washing is not an option, the alternative is dry brushing using a very soft brush over a sieve. When cleaning teeth, it is important not to create artificial microwear patterns or remove dental calculus deposits. Before the skeletal remains are stored, they should be fully dried, to prevent mold growth.⁸

Use of Insects

Carrion beetles has been shown to be an advantageous way to remove soft tissue from bone.² Dermestid beetles are the most useful of the carrion beetles for cleaning bones, especially for the parts of the skeleton which are difficult to dissect by hand.¹ As beetle larva do not alter the bones themselves there is far less chance that bone preservation will be compromised, however, dermestid beetles can take several weeks to remove soft tissues from the remains.²

Use of Chemicals

Inorganic chemicals used for cleaning bones include antiformin, ammonium hydroxide, sodium hydroxide and other alkaline solutions. Maceration with organic chemicals can also be performed with enzymes such as papain or pepsin or with washing powders containing enzymes.¹ This is a very fast way to processes remains, however, it has a high chance of damaging the bones themselves.² Cleaning treatments using bleach, hydrogen peroxide, ethylenediaminetetraacetic acid/papain, room temperature water and detergent/sodium carbonate followed by degreasing has additionally led to low DNA concentrations.¹

As forensic pathologist increasingly relies on the forensic anthropologist to be the consulting expert in human identification, especially if identification is not possible from visual inspection of skeletal remains, the forensic biologist may be called upon to conduct DNA analysis. The possibility of downstream DNA testing needs to be considered when skeletal preparation techniques are employed to deflesh human remains, as they have the potential to strongly impact genetic analyses and subsequent identification.¹

If the remains are particularly fragile, they may require conservation. However, the use of consolidants and reconstruction materials may compromise future biomolecular and chemical analyses, thus minimum intervention is recommended and only when important information can be gained, such as reconstructing long bone lengths or cross-sections.⁸

Commingling

The term commingled is applied to any burial assemblage in which individual skeletons are not separated into separate burials. Commingled assemblages occur in cases of familial burials (e.g., multiple family members buried in a single grave plot) and mass graves, possibly the result of genocide.³ Each assemblage reaching the lab will have specific properties depending on the depositional environment, the type of commingling and the extent to which articulated elements and elements belonging to the same skeleton which more generally has already been identified through careful excavation.⁹ However, if remains arrive at the lab and several bodies are still commingled.²

Bone/Tooth Inventory

Once the human skeletal remains have been separated from all other materials/remains in the assemblage, the first step in their analysis is the construction of a careful inventory. During inventorying, it is imperative to retain all contextual information (site number, inventory number given in the field etc.). The extent and nature of the inventory are problem-driven but any inventory should document in appropriate detail what bones or parts of bone are present per individual. ⁷ The bone and tooth inventory in cases of commingled remains will include each skeletal/dental element or bone/ tooth fragment as a separate entry. However, upon sorting the remains, elements belonging to the same individual must be noted as such in the database. Bone fragments too small to identify should be divided in broad categories (e.g. cortical bone/trabecular bone, cranial bone/post-cranial bone, axial skeleton/appendicular skeleton), sorted by size class based on maximum dimension, counted and weighted.⁹

Sorting Procedures

During sorting, the bones belonging to each individual are identified (individuation process). Depending on the nature of the commingled assemblage (state of bone preservation, sample size, degree of commingling), this step may take place before the inventory and, subsequently, the remains should be inventoried per skeleton rather than per element. The first step of the sorting process involves the conjoining of fragmentary remains to the greatest extent possible. Bones should then be sorted by element type, side, and size using the most appropriate among the available techniques: visual pairmatching, articulation, process of elimination, osteometric comparison, and taphonomy. Elements that were articulated at the time of recovery should be maintained as a unit. Components of the biological profile (e.g., age-at-death, sex, and stature) may also be useful in the sorting process. Sorting procedures should be used in conjunction with each other, as well as with contextual scene information. After all macroscopic techniques have been used, chemical analysis and DNA profile data may be employed.⁹

Visual Pair-Matching

Visual pair-matching refers to the association of left–right elements based on morphological similarities. Overall bone size and robusticity are the primary factors examined, while nonmetric traits (e.g., third trochanter) can offer additional help in identifying paired elements. If the elements under study preserve age or sex markers (e.g. unfused epiphyses, pubic symphysis etc.), these are also important to take into consideration in pairing.⁹

Articulation

The size and shape of adjoining bones is correlated as they form a functional joint. However, the strength of association varies depending on the elements considered, thus not all joints will be equally useful in sorting.9 The most accurate joints to use a larger congruent joints.²

Size (osteometric sorting)

Osteometric sorting tests the null hypothesis that the two bones under examination are similar enough in size and shape to have originated from the same individual. It may be used for pairing bilateral elements, matching articulated elements, or identifying bones belonging to the same individual based on their relative size. Nonetheless, this method is only applicable to well-preserved skeletal elements, and it will be of limited, if any, use to highly fragmented material.⁹

Pair-matching Method 1

There are some statistical software’s where different measurements are input, and the program considers all possible pairings. If the pairwise differences are below the acceptable user-defined threshold, the right and the left element under examination are given as a potential pair. This method is a way to “prescreen” possible pairs and minimizes the time required to visually match the bones. Among the advantages of this method is that it is simple in its implementation, the user can employ any measurement he/she wishes, and additionally to bone measurements, the calculations can incorporate the degree of expression of osteoarthritic changes.⁹

Par-matching Method 2

An alternative method for osteometric pair matching compares a calculated M-statistic, which expresses the metric similarity of bilateral elements, to a reference sample. ⁹ The M-statistic is calculated using the following equation, where L and R represent left and right bilateral measurements, respectively:⁹

M= [L-R] / ((L+R)/2) ²

The null hypothesis that two homologs are from the same individual can be tested by calculating the value of M for each measurement for the bones in question and comparing it to the 90th and 95th percentiles or the maximum value of M from a reference table (not pictured here). If the value of M is greater than that for the chosen percentile, the null hypothesis can be rejected, suggesting that the bones under examination are unlikely to have originated from the same individual.⁹

Taphonomy

Taphonomic patterns can be used for skeletal reassociation. Skeletal remains in different locations within a grave may be exposed to different taphonomic agents and the resulting bone alterations may be used to sort individuals exposed to different taphonomic processes during primary inhumation, who became commingled at a later stage. However, taphonomy must be used with caution in the sorting process as taphonomic differences can also be observed on the remains of a single individual, especially if they occurred post-disarticulation.⁹

Age

The size and maturity of the skeletal remains can be particularly helpful in discriminating the remains of adult from nonadult remains.⁹

Chemical Analysis

Recent research using X-ray fluorescence (XRF) spectrometry and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) have shown promise in determining whether a set of remains belongs to a single or multiple individuals by analyzing the elemental concentration in human bones. Note that the former technique is non-destructive, while the latter requires part of the bone to be destroyed during analysis. However, they both can be used to determine inter-skeletal differences in bone mineral composition which may be due to ingesting food and water, metabolic functions, chemical exposure or other means of absorption. A confounding factor is that trace elements are stored differently throughout the human skeleton, thus, within skeleton variability in elemental composition may exceed individual variability. Trace elemental signatures also vary throughout an individual’s lifespan due to age-related metabolic and physiological functions. Another confounding factor is postmortem contamination (diagenesis), which may alter the elemental concentrations in buried human bones. However, surface contamination should not be an issue as x-rays penetrate the bone surface by several millimeters during chemical analysis.⁹

DNA

DNA analysis is increasingly employed in commingling cases. In osteo-archaeological analysis, ancient DNA data mostly aim at addressing issues of kinship, migration patterns and genetic diseases, while in forensic contexts the aim of DNA analysis is the identification of the unknown individuals. Given its cost and destructive nature, DNA analysis should be best used in conjunction with the context of the remains and the results of the macroscopic skeletal analysis.⁹

ESTIMATION OF THE NUMBER OF INDIVIDUALS

Another assessment that an anthropologist can perform is the calculation of the number of individuals in a mixed burial assemblage. Because not all burials consist of a single individual, it is important to be able to estimate the number of individuals in both an archaeological and forensic context. Quantification of the number of individuals in a burial assemblage can be done through the application of a number of methods, including the following: the Minimum Number of Individuals (MNI) and the Most Likely Number of Individuals (MLNI). The most commonly used method in physical anthropology, and the focus of this section, is determination of the MNI.³

Minimum Number of Individuals (MNI)

The MNI expresses the least number of individuals required to account for the skeletal elements present in the assemblage that has been recovered. The most common way to estimate the MNI is by sorting the bones by side and element and then taking the most frequent element as the estimate. In other words, the MNI is equal to the most repeated element after sorting by element and side: Max (L, R). In cases of fragmentary remains, make sure that there is an overlap of anatomical features on the fragmented remains (e.g. greater trochanter) in order to avoid counting the same individuals more than once.⁹

In some contexts, MNI may be inferred from the biological profile of the elements. For example, the presence of some elements clearly suggestive of a male individual and others suggestive of a female, indicate that at least two individuals were buried together. Similarly, the observation of considerable differences in bone size, especially between bilateral or adjoining elements, also supports the presence of multiple individuals. Even though MNI can provide useful information on the smallest number of individuals that comprise the assemblage, they underestimate the true sample size whenever the recovery rates are less than 100%, which is often the case in archaeological assemblages.⁹

Most Likely Number of Individuals (MLNI)

MLNI estimates assess the initial number of individuals that comprised the assemblage under study by identifying the number of P (pairs) between R (right) and L (left) bones. When using the MLNI, it is important that probabilities of sampling the left and right sides within individuals are independent.⁹ An estimate of the original assemblage represented by the skeletal elements is determined by:

MLNI= [(L+1)(R+1)/ (P+1)]-1 ²

MNI versus MLNI

The MLNI estimates the original number of individuals that comprised the skeletal assemblage, whereas the MNI expresses only a minimum estimate. Furthermore, it is possible to provide confidence intervals with the MLNI, but not with the MNI. Thus, the MLNI should be preferred over the MNI, but in highly fragmented remains, estimation of the MNI may be the only viable option.⁹

Landmarks and Measurements of the Skull

Standardized landmarks and measurements of the skull and post-cranium are necessary in order to compare validity as part of the scientific method. These measurements can be used to determine sex, biological affinity, stature, modernity, and specific facial features in the remains of an unknown individual. Therefore, it is necessary to use agreed upon landmarks on the skull from which the measurements can be taken. To increase reliability, an individual researcher should take the same measurements on an individual(s) several times over the course of a few days to estimate intra-observer error. Research partners should undertake the same process to determine what the error rate may be between researchers, inter-observer error. The following list of landmarks and basic measurements will aid in learning standardized methodology used in osteological research.¹⁴

Landmarks

Alveolare– The bony crest located between the central maxillary incisors.¹⁴

Alare– Determined using sliding calipers placed on the most lateral margins of the nasal aperture.¹⁴

Basion– Point located on the anterior border of the foramen magnum.¹⁴

Bregma– The point where the sagittal suture meets the coronal suture anteriorly.¹⁴

Dacryon– Located in the medial aspect of the orbits, the point where the maxilla, lacrimal, and frontal meet.¹⁴

Ectoconchion– Located at the intersection of the frontal and zygomatic, on the medial aspect.¹⁴

Euryon– Determined using spreading calipers placed on the posterior parietals at the greatest breadth.¹⁴

Frontotemporale– Located on each of the temporal lines of the frontal in the area of greatest constriction.¹⁴

Glabella– The point superior to the nasal bones, between the supraorbital ridges.¹⁴

Gnathion– The central point on the inferior aspect of the mandibular body in the region of the mental eminence.¹⁴

Infradentale– The bony crest located between the mandibular central incisors.¹⁴

Lambda– The intersection point of the lambdoidal suture and the sagittal suture.¹⁴

Nasion– The point located most superiorly where the nasal bones meet.¹⁴

Nasiospinale– The point where the midsagittal plane intersects the inferior margin of the nasal aperture.¹⁴

Opisthion– The most medial point on the posterior aspect of the foramen magnum.¹⁴

Opisthocranion– Most posterior aspect of the skull, excluding the area around the external occipital protuberance.¹⁴

Orbitale– The most inferior point on the lower orbital margin.¹⁴

Prosthion– On the upper alveolar process, this is the most anterior point at midline.¹⁴

Zygion– Determined using spreading calipers placed on the most lateral aspects of the zygomatic arches.¹⁴

Measurements (These are only an example of some of the measurements that can be taken of the skull and there are many more measurements that can be taken of the postcranial skeleton.)

Basion-Bregma– Taken using the spreading calipers; one end of the calipers is placed on the medial aspect of the rim of the foramen magnum (basion) and the other end is placed at intersection of the coronal and sagittal sutures (bregma).¹⁴

Bizygomatic– Taken using the spreading calipers; one end of the calipers goes to the most lateral aspect of each of the zygomatic arches (zygoma to zygoma).¹⁴

Cranial breadth– Taken using the spreading calipers; one end of the calipers goes to the most lateral aspect of each of the parietals (euryon to euryon).¹⁴

Cranial length– Taken using the spreading calipers; one end of the calipers is placed just superior to the frontonasal suture on the most anterior aspect of the frontal (glabella), while the other is placed at the most posterior aspect of the skull (opisthocranion).¹⁴

Minimum frontal breadth– Taken using the spreading calipers; one end of the calipers is placed on each of the temporal lines of the frontal in the area of greatest constriction (frontotemporale to frontotemporale).¹⁴

Nasal breadth– Measurement is taken from alare to alare, to obtain the maximum breadth; use spreading calipers.¹⁴

Nasal height– Measurement is taken from nasion to nasiospinale; use sliding calipers.¹⁴

Orbital breadth– Measurement is taken from dacryon to ectoconchion; use spreading calipers.¹⁴

Orbital height– Measurement is taken perpendicular to the horizontal axis of the orbit; use spreading calipers.¹⁴

Total facial height– Measurement is taken from nasion to gnathion with teeth in occlusion; use sliding calipers.¹⁴

Upper facial height– Measurement is taken from nasion to alveolare (does not include height of the mandible); use sliding calipers.¹⁴

Statistics

The measurements listed in the section above can also be used in a statistical analysis to estimate sex and ancestry. In fact statistical analysis is becoming more and more important to the field of Forensic Anthropology. For this reason, is important to understand some basic statistical terminology.

Mean

The words mean and average are often used interchangeably. If you were to take three exams in your math classes and obtain scores of 86, 75, and 92, you would calculate your mean score by adding the three exam scores and dividing by three (your mean score would be 84.3 to one decimal place).⁴

Median

Median is a number that measures the “center” of the data. You can think of the median as the “middle value,” but it does not actually have to be one of the observed values. It is a number that separates ordered data into halves. Half the values are the same number or smaller than the median, and half the values are the same number or larger. For example, consider the following data.⁴

1; 11.5; 6; 7.2; 4; 8; 9; 10; 6.8; 8.3; 2; 2; 10; 1

Ordered from smallest to largest:

1; 1; 2; 2; 4; 6; 6.8; 7.2; 8; 8.3; 9; 10; 10; 11.5

Since there are 14 observations, the median is between the seventh value, 6.8, and the eighth value, 7.2. To find the median, add the two values together and divide by two.⁴

Mode

Another measure of the center is the mode. The mode is the most frequent value. There can be more than one mode in a data set as long as those values have the same frequency, and that frequency is the highest. A data set with two modes is called bimodal.⁴

Standard Deviation

The most common measure of variation, or spread, is the standard deviation. The standard deviation is a number that measures how far data values are from their mean. The standard deviation also provides a numerical measure of the overall amount of variation in a data set and can be used to determine whether a particular data value is close to or far from the mean. The standard deviation is always positive or zero. The standard deviation is small when the data are all concentrated close to the mean, exhibiting little variation or spread. The standard deviation is larger when the data values are more spread out from the mean, exhibiting more variation.⁴

Errors

When you analyze data, it is important to be aware of sampling errors and non-sampling errors. The actual process of sampling causes sampling errors. For example, the sample may not be large enough. Factors not related to the sampling process cause non-sampling error.⁵

Sampling Error

In reality, a sample will never be exactly representative of the population so there will always be some sampling error. As a rule, the larger the sample, the smaller the sampling error. In statistics, a sampling bias is created when a sample is collected from a population and some members of the population are not as likely to be chosen as others. Remember, each member of the population should have an equally likely chance of being chosen. When a sampling bias happens, there can be incorrect conclusions drawn about the population that is being studied. For instance, if a survey of all students is conducted only during noon lunchtime hours is biased. This is because the students who do not have a noon lunchtime would not be included.⁵

Non-Sampling Error

Non-sampling error is an issue that affects the reliability of sampling data other than natural variation; it includes a variety of human errors including poor study design, biased sampling methods, inaccurate information provided by study participants, data entry errors, and poor analysis.⁵ When an error occurs because of a mistake or intentional fraud it is called Practitioner error. When an error occurs because of a piece of technology than this is called Instrument error. The possibility of instrument error can be lessened if a machine is properly calibrated and maintained. Statistical errors are often a reflection of natural variability found within the sample but can still cause a deviation from the actual value. Finally, a methodologically error occurs because the method itself has limitations.²

Types of Statistical Analysis

There are two types of statistical analysis that are used in Forensic Anthropology. These are Discriminant Function and Regression analysis. Discriminant Function analysis is used when anthropologists are trying to estimate sex and ancestry in skeletal remains because it allows membership in a particular group to be predicted. Either with postcranial or cranial measurements. Regression analysis is used to estimate stature because this type of analysis analyzes the relationship between at least two variables. In the case of stature, the relationship being analyzed is between bone length and height.²

Fordisc

The computer program Fordisc is an anthropological tool used to estimate different components of the biological profile, including ancestry, sex, and stature. When using Fordisc, skeletal measurements are input into the computer software and the program employs multivariate statistical classification methods, including discriminant function analysis, to generate a statistically validated prediction for the geographic origin or sex of unknown remains. Fordisc will also tell the analyst the likelihood of the prediction being correct, as well as how typical the metric data is for the assigned group.³

The results from FORDISC will have several columns and look like the table below:

Group	Classified Into	Distance From	Posterior Probability	Type F Probability	Type Chi Probability	Type R Probability
AM	AM	4.3	.99	.92	.91	.89
HM		10.7	.01	.60	.29	.46
BM		16.3	.003	.34	.09	.14

                                                                  Table 1: Table layout of FORDISC results

The first column, Group, list the groups the analysis was limited to, as on FORDISC an analysis can be limited by sex and ancestry. In this case AM (Asian Male), HM (Hispanic Male), and BM (Black Male) were included. The next column, classified into, is which of the options the skeleton has been assigned to. In this case the skeleton has been classified as an Asian Male. The column distance from is a measure of how far the skeleton is from the different groups chosen. The skeleton will be classified into the group it is closest to. Posterior Probability determines how far the skeleton is from a particular group when compared to other groups. If this column list a group as being under .1 they can be excluded from the analyses. The final three columns assess how typical or similar a skeleton is to the chosen groups. If one of these columns list a group as being under .01 they can be excluded from the analyses.²

What Is An Isotope?

Neutrons and protons are the two fundamental particles that make up the nucleus of an atom. Those two particles, collectively called nucleons, make up the small interior portion of the atom. Both particles have nearly the same mass and each of the particles is significantly more massive than the electron.¹²

The atomic number represents the number of protons within a nucleus. That value determines the elemental quality of each atom. Every carbon atom, for instance, has atomic number of 6, whereas every oxygen atom has an atomic number of 8.¹²

When describing the mass of objects on the scale of atoms, it is most reasonable to measure their mass in terms of atoms. The atomic mass unit (u) was originally defined so that a neutral carbon atom would have a mass of exactly 12 u. Given that protons and neutrons are approximately the same mass, than there are six protons and six neutrons in an carbon atom.¹²

How does the mass number help to differentiate one atom from another? The intent of the mass number is to differentiate between various isotope of an atom. The term isotope refers to the variation of atoms based upon the number of neutrons within their nucleus. While it is most common for there to be six neutrons accompanying the six protons within a carbon atom, it is possible to find carbon atoms with seven neutrons or eight neutrons. Those carbon atoms are respectively referred to as carbon-13 and carbon-14 atoms, with their mass numbers being their primary distinction. The isotope distinction is an important one to make, as the number of neutrons within an atom can affect a number of its properties, not the least of which is nuclear stability.¹²

Isotope Analysis

Isotopes have gained popularity for reconstructing the mobility of now-dead individuals or extinct animals in archaeology and paleoecology. Isotopes are ubiquitous in organic tissues and vary predictably in the environment with biological and physical processes. For several isotopic systems such as hydrogen, carbon or oxygen, the variations in isotopic abundances vary spatially, and these patterns are transmitted from inorganic (e.g., water, carbon dioxide) into organic tissues with some isotopic loss. As human and animal eat and drink, their organic tissues inherit an isotopic fingerprint from the local ecosystems that relate to the geographic location where the tissue was grown. In tissue with slow turnover rate (e.g., teeth, bones), the isotopic fingerprint is preserved post-mortem and is used to infer where they grew up (the provenance) or mobility of individuals.⁶

However, to obtain precise and unbiased information, isotopes analyzed in a tissue of interest needs to be compared to an isotopic baseline. Without these baselines, isotope data from individuals can only be compared with each other or with existing databases. While these points-to-points comparisons can be useful, they are spatially biased, limited, and often ambiguous. A more quantitative approach to isotope provenancing is to use continuous-surface geographic assignment by comparing the measured isotope data in animal tissue to a map predicting isotope variations across the landscape, also called an isoscape. This approach incorporates uncertainty and produces continuous-probability surfaces to visualize potential location of origin over an entire study area. Once generated, the probability surfaces from multiple isotopic systems are combined to summarize all provenance data into a probabilistic visual.⁶

Two isotopic systems, hydrogen/oxygen isotopes and strontium isotopes, have well-calibrated isoscapes, allowing continuous-surface assignment approaches in archaeology, forensic anthropology, and paleoecology. The oxygen isotope composition (δ¹⁸O) of human and animal tissues that drink regularly (‘obligate drinkers’) mainly reflects the isotope composition of the local drinking water. Consequently, the isotopic composition measured in hard tissues (e.g., teeth enamel, bones) can be used to predict the isotopic composition of the water consumed by individuals using equations that account for metabolic isotopic loss. The oxygen isotope composition of the local precipitation, which controls the isotopic composition of local waters, is strongly influenced by climatic and geographic factors such as temperature, latitude, altitude and distance from the coast. These δ¹⁸O patterns in precipitation have been predicted at the global scale using existing isotopic data and geostatistical approaches.⁶

Strontium is predominantly transmitted to human tissues through ingested food. Strontium isotope ratios (⁸⁷Sr/⁸⁶Sr) are usually analyzed on teeth enamel because Sr is abundant in calcified tissues. ⁸⁷Sr/⁸⁶Sr variations on the landscape vary at high resolution and are strongly influenced by the local geology. The isotope ratios are influenced by the age of the bedrock, the type of bedrock, its initial content in rubidium and the initial ⁸⁷Sr/⁸⁶Sr ratio at the time of the rock formation.⁶

Spatially distributed isotope datasets can also be used to address the question of ancestry. Stable isotope analysis is an effective geolocation tool since isotopes provide a record of movement and eating habits of an individual throughout life. Isotope analysis can be especially useful with identification of likely migrants.¹⁰ 

Radiological Analysis

Radiology is the study of internal structures of the body as seen with the help of high energy radiation. The use of radiographs, the images created through the use of this technology, can be beneficial to a forensic anthropologist in several ways. Including diagnosis of pathologies, identification using features like the frontal sinus or dentition, aging, trauma analysis, and locating bullets or other foreign bodies. This is also a nondestructive method of study.²

On a radiograph bone looks lighter or more radiopaque than soft tissue. This occurs because bone is denser than soft tissue and blocks more of the radiation as it passes through the body. Denser still materials, like metal, will block even more of the beam and thus appear even lighter in a radiograph. This makes it possible to locate bullets even if they have fragmented as the metal chunks will be lighter than both the bones and soft tissues.² There are several types of radiographic analysis that can be used, including:

X-Rays

German physicist Wilhelm Röntgen (1845–1923) was experimenting with electrical current when he discovered that a mysterious and invisible “ray” would pass through his flesh but leave an outline of his bones on a screen coated with a metal compound. In 1895, Röntgen made the first durable record of the internal parts of a living human: an “X-ray” image (as it came to be called) of his wife’s hand. Scientists around the world quickly began their own experiments with X-rays, and by 1900, X-rays were widely used to detect a variety of injuries and diseases. In 1901, Röntgen was awarded the first Nobel Prize for physics for his work in this field.¹¹

The X-ray is a form of high energy electromagnetic radiation with a short wavelength capable of penetrating solids and ionizing gases. As they are used in medicine, X-rays are emitted from an X-ray machine and directed toward a specially treated metallic plate placed behind the patient’s body. The beam of radiation results in darkening of the X-ray plate. X-rays are slightly impeded by soft tissues, which show up as gray on the X-ray plate, whereas hard tissues, such as bone, largely block the rays, producing a light-toned “shadow.” Thus, X-rays are best used to visualize hard body structures such as teeth and bones. Like many forms of high energy radiation, however, X-rays are capable of damaging cells and initiating changes that can lead to cancer. This danger of excessive exposure to X-rays was not fully appreciated for many years after their widespread use.¹¹

Refinements and enhancements of X-ray techniques have continued throughout the twentieth and twenty-first centuries. Although often supplanted by more sophisticated imaging techniques, the X-ray remains a “workhorse” in medical imaging, especially for viewing fractures and for dentistry. The disadvantage of irradiation to the patient and the operator is now attenuated by proper shielding and by limiting exposure.11

Modern Medical Imaging

X-rays can depict a two-dimensional image of a body region, and only from a single angle. In contrast, more recent medical imaging technologies produce data that is integrated and analyzed by computers to produce three-dimensional images or images that reveal aspects of body functioning.¹¹

Computed Tomography

Tomography refers to imaging by sections. Computed tomography (CT) is a noninvasive imaging technique that uses computers to analyze several cross-sectional X-rays in order to reveal minute details about structures in the body. The technique was invented in the 1970s and is based on the principle that, as X-rays pass through the body, they are absorbed or reflected at different levels. In the technique, a patient lies on a motorized platform while a computerized axial tomography (CAT) scanner rotates 360 degrees around the patient, taking X-ray images. A computer combines these images into a two-dimensional view of the scanned area, or “slice.”¹¹

Since 1970, the development of more powerful computers and more sophisticated software has made CT scanning routine for many types of diagnostic evaluations. It is especially useful for soft tissue scanning, such as of the brain and the thoracic and abdominal viscera. Its level of detail is so precise that it can allow physicians to measure the size of a mass down to a millimeter. The main disadvantage of CT scanning is that it exposes patients to a dose of radiation many times higher than that of X-rays. In fact, children who undergo CT scans are at increased risk of developing cancer, as are adults who have multiple CT scans.¹¹

Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) is a noninvasive medical imaging technique based on a phenomenon of nuclear physics discovered in the 1930s, in which matter exposed to magnetic fields and radio waves was found to emit radio signals. In 1970, a physician and researcher named Raymond Damadian noticed that malignant (cancerous) tissue gave off different signals than normal body tissue. He applied for a patent for the first MRI scanning device, which was in use clinically by the early 1980s. The early MRI scanners were crude, but advances in digital computing and electronics led to their advancement over any other technique for precise imaging, especially to discover tumors. MRI also has the major advantage of not exposing patients to radiation. Drawbacks of MRI scans include their much higher cost, and patients with iron-containing metallic implants (internal sutures, some prosthetic devices, and so on) cannot undergo MRI scanning because it can dislodge these implants. 11

Ultrasonography

Ultrasonography is an imaging technique that uses the transmission of high-frequency sound waves into the body to generate an echo signal that is converted by a computer into a real-time image of anatomy and physiology. Ultrasonography is the least invasive of all imaging techniques, and it is therefore used more freely in sensitive situations such as pregnancy. The technology was first developed in the 1940s and 1950s. Ultrasonography is used to study heart function, blood flow in the neck or extremities, certain conditions such as gallbladder disease, and fetal growth and development. The main disadvantages of ultrasonography are that the image quality is heavily operator-dependent and that it is unable to penetrate bone and gas.11

X-Ray fluorescence (XRF): X-Ray fluorescence is used for the determining of mineral content of bone such as Zn, Pb, and Fe. The presence of these elements at different quantity helps in determination of diet of an individual and the abundance of these elements in the bones also helps in determining the area to which an individual belongs. The main advantage of this technique is that this technique takes less time for examination.¹³

 

References:

1. Abayomi Ajayi, Odiri Edjomariegwe, and Iselaiye O.T, “A Review of Bone Preparation Techniques for Anatomical Studies,” Malaya Journal of Biosciences 3 (2016):76-80. https://www.researchgate.net/publication/313841692_A_review_of_bone_preparation_techniques_for_anatomical_studies.

2. Angi M. Christensen, Nicholas V. Passalacqua, and Eric J. Bartelink, Forensic Anthropology: Current Methods and Practice, 2nd ed. (London: Academic Press, 2019): 38, 88-104 and 218-230.

3. Ashley Kendell, Alex Perrone, and Colleen Milligan, “Bioarcheology and Forensic Anthropology” In Explorations, ed. Beth Shook, Katie Nelson, Kelsie Aguilera and Lara Braff (Arlington: American Anthropological Association, 2019). https://pressbooksdev.oer.hawaii.edu/explorationsbioanth/chapter/osteology/.

4. Barbara Illowsky, Susan Dean, Daniel Birmajer, Bryan Blount, Sheri Boyd, Matthew Einsohn, James Helmreich, Lynette Kenyon, Sheldon Lee, and Jeff Taub, Introductory Statistics (Houston: Rice University, 2013). https://openstax.org/details/books/introductory-statistics.

5. Barbara Illowsky, Susan Dean, Daniel Birmajer, Bryan Blount, Sheri Boyd, Matthew Einsohn, James Helmreich, Lynette Kenyon, Sheldon Lee, and Jeff Taub, Statistics (Houston: Rice University, 2020). https://openstax.org/details/books/statistics.

6. Clément P. Bataille, Klervia Jaouen, Stefania Milano, Manuel Trost, Sven Steinbrenner, Éric Crubézy, Rozenn Colleter, “Triple sulfur-oxygen-strontium isotopes probabilistic geographic assignment of archaeological remains using a novel sulfur isoscape of western Europe,” PLoS One 16 (2021). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8099095/.

7. Efthymia Nikita, AN INTRODUCTION TO THE STUDY OF BURNED HUMAN SKELETAL REMAINS Guide No. 4 (The Cyprus Institute Science and Technology in Archaeology and Culture Research Center, 2021), 7-8. https://repository.cyi.ac.cy/bitstream/CyI/933/1/AN_INTRODUCTION_TO_THE_STUDY_OF_BURNED_H.pdf.

8. Efthymia Nikita, Anna Karligkioti & Hannah Lee, EXCAVATION AND STUDY OF COMMINGLED HUMAN SKELETAL REMAINS Guide No. 1 (The Cyprus Institute Science and Technology in Archaeology and Culture Research Center, 2019), 10, 14, and 21. file:///C:/Users/lbail/Downloads/BASIC_GUIDELINES_FOR_THE_EXCAVATION_AND_STUDY_OF_HUMAN_SKELETAL_REMAINS_GUIDE_1.pdf.

9. Efthymia Nikita, Anna Karligkioti & Hannah Lee, EXCAVATION AND STUDY OF COMMINGLED HUMAN SKELETAL REMAINS Guide No. 2 (The Cyprus Institute Science and Technology in Archaeology and Culture Research Center, 2019), 5-13, 17-20. https://www.researchgate.net/profile/Anna-Karligkioti/publication/338987251_EXCAVATION_AND_STUDY_OF_COMMINGLED_HUMAN_SKELETAL_REMAINS/links/60265b9a45851589399b5e77/EXCAVATION-AND-STUDY-OF-COMMINGLED-HUMAN-SKELETAL-REMAINS.pdf.

10. Eugénia Cunha and Douglas H. Ubelaker, “Evaluation of Ancestry from Human Skeletal Remains: A Concise Review,” Evaluation of Ancestry from Human Skeletal Remains: A Concise Review,” Forensic Sciences Research 5 (2020): 89–97. https://doi.org/10.1080/20961790.2019.1697060.

11. J. Gordon Betts, Kelly A. Young, James A. Wise, Eddie Johnson, Brandon Poe, Dean H. Kruse, Oksana Korol, Jody E. Johnson, Mark Womble, Peter DeSaix, William Blaker, Julie Bowers, Matthew Barlow, Michael Hortsch, Emily Bradshaw, Kathleen Tallman, Boyd Campbell, Rohinton Tarapore, Branko Jablanovic, Pamela Dobbins, Brian Shmaefsky, Barbara Christie-Pope, Douglas Sizemore, Maurice Culver, Debra McLaughlin, Bruce Maring, Peter Dukehart, Susan Dentel, Elizabeth Tattersall, Margaret Weck, Neil Westergaard, Marnie Chapman, William Kleinelp, Brenda Leady, Susanna Heinze, Julie May, Ann Caplea, Kim Aaronson, Lopamudra Agarwal, Gary Allen, Nishi Bryska, Susan Caley Opsal, Norman Johnson, Sarah Leupen, Robert Mallet, Kenneth Crane, Heather Cushman, Chaya Gopalan, Mark Hubley, Dale Horeth, Kathleen Weiss, Sharon Ellerton, Janis Thompson, Rita Thrasher, Nicholas Mitchell, David Van Wylen, Elisabeth Martin, Ivan Paul, Lihua Liang, David Wortham, Shobhana Natarajan, Betsy Ott, Sondra Dubowsky, Mary Jane Niles, Mark Thomas, Mike Pyle, Umesh Yadav, Ann Henninger, Elizabeth DuPriest, Timothy Ballard, Phillip Nicotera, Michael Giangrande, Natalie Maxwell, Cameron Perkins, Robert Rawding, Lynn Gargan, Jeff Keyte, Victor Greco, Robert Allison, Heather Armbruster, Lynn Wandrey, David Pfeiffer, Mark Jonasson, Susan Spencer, Leigh Kleinert, Jason Schreer, Thomas Pilat, Ikemefuna Nwosu, Patty Dolan, Ellen DuPré, John Lepri, Carla Endres, Eileen Preston, Eric Sun, Tom Swenson, Tony Yates, Justin York, Cheri Zao, Elena Zoubina, Noelle Cutter, Lynnette Danzl-Tauer, Myriam Feldman, Jane Davis, Rosemary Hubbard, Aaron Payette, Greg Fitch, Robert Sullivan, AnnMarie DelliPizzi, Cynthia Standley, Shobhana Natarajan, Scott Payne, Laird Sheldahl, and Pam Elf, Anatomy and Physiology (Houston: Rice University, 2013). https://openstax.org/details/books/anatomy-and-physiology

12. Paul Peter Urone, Roger Hinrichs, Fatih Gozuacik, Denise Pattison, and Catherine Tabor, Physics (Houston: Rice University, 2020). https://openstax.org/details/books/physics.

13. Purva Wagisha Upadhyay and Amarnath Mishra, “Forensic Anthropology” in Biological Anthropology – Applications and Case Studies, ed. Alessio Vovlas (London: IntechOpen, 2021). https://www.intechopen.com/chapters/73372.

14. Roberta Hall, Kenneth Beals, Holm Neumann, Georg Neumann, and Gwyn Madden, Introduction to Human Osteology (Michigan: Grand Valley State University, 2010). https://pressbooks.gvsu.edu/introhumanosteology/.