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Anthropology: Taphonomy in the Forensic Context
Anthropology: Taphonomy in the Forensic Context S Blau, Monash University, Melbourne, VIC, Australia and Victorian Institute of Forensic Medicine, Southbank, VIC, Australia S Forbes, University of Technology, Sydney, NSW, Australia r 2016 Elsevier Ltd. All rights reserved. This article is a revision of the previous edition article by W.D. Haglund, M.H. Sorg, volume 1, pp 94–100, © 2005, Elsevier Ltd.
Abstract This chapter defines the term ‘taphonomy’ and summarizes the history of the study as pursued in various disciplines. Intrinsic and extrinsic variables that affect preservation of human remains are summarized. This is followed by an examination of the questions that forensic taphonomy can potentially address, including: what is the estimated time since death/postmortem interval or time since deposition/post-burial interval?; how did the remains come to be where they were located or discovered?; what actions may have taken place to conceal the victim’s identity or the crime?; and which factors effect injury interpretation, specifically, differentiating perimortem trauma from postmortem changes?
Glossary Adipocere formation The chemical conversion of adipose tissue into a solid substance comprising predominantly saturated fatty acids. Autolysis Enzymatic degradation of cells or tissues. Biomass Biological material derived from living or recently living organisms. Biostratinomy The sedimentary history of a fossil from death to the final burial. Diagenesis Chemical and physical alteration of sediments during rock formation.
Introduction The term taphonomy originates from the Greek taphos – τάφος (meaning burial), and nomos – νόμος (meaning law), and is defined as the study of the transition of plant and animal organisms after death from the biosphere (living surfaces) to the lithosphere (underground) (Blau, 2014). Taphonomists study environmental and anthropogenic actions and processes (both cultural and individual) that affect the remains of biological organisms from the time of death to discovery (Nawrocki, 2009). Taphonomy was first defined by the Russian paleontologist, Efremov (1940), although the science of taphonomy had been practiced for centuries preceding this definition (Cadee, 1991). Taphonomic studies were traditionally the focus of paleontologists who were interested in understanding the processes of fossilization from death to diagenesis (Martin, 1999). Weigelt (1927; translated in 1989) provided one of the most thorough descriptions of decomposition, including transport of remains, and burial of carcasses on the edge of a lake in
Encyclopedia of Forensic and Legal Medicine, Volume 1
Disarticulation A separation at the joints. Microorganisms A microscopic organism such as bacteria or fungus. Mummification The rapid loss of moisture from soft tissue through the process of desiccation. pH It is a measure of the acidity of an aqueous solution. Soil pH is measured on a logarithmic scale and is determined by the concentration of hydrogen ions. Putrefaction Microbial degradation of cells or tissues.
the US Gulf Coast following a massive mortality of cattle due to severe climatic conditions. His study was the first investigation to thoroughly document the sedimentary history of fossils from death to decomposition (necrolysis) through to the final burial; these processes are referred to as biostratinomy. During the 1970s, paleoanthropologists and archeologists “began to study taphonomy in order to determine how and why floral and faunal remains accumulated and differentially preserved within the archeological record” (Forbes, 2014a). Archeologists examine both natural and human induced (cultural) processes. Studies include bone modification by scavenger species, and butchering modification by modern hunter–gatherer people in order to differentiate the taphonomic signatures of nonhuman scavengers from that of human cultural food preparation. Models of bone weathering have been developed and experiments devised to simulate the effects of transportation by rivers on different types of bones (e.g., Behrensmeyer, 1978). Some scientists have observed particular species or environmental processes as they occur in nature while
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others have performed actualistic or experimental research. These efforts produced models that could be applied to archeological and forensic cases (see Beary and Lyman, 2012 for a history of taphonomy research). In the 1980s, taphonomic approaches were adopted by several of the forensic sciences because of the value the discipline added to understanding what happens to a body from the time immediately after death to the point of recovery. This included excavation, post-recovery transport (Beary and Lyman, 2012: 517–518), autopsy examination and other forensic analyses (Dirkmaat and Passacalcqua, 2012). Specifically, researchers were most interested in estimating time since death, reconstructing the events surrounding death and pre- and post-burial, and discriminating between bone modifications resulting from human behavior and those caused by taphonomic factors (Haglund and Sorg, 1997a; Ubelaker, 1997). The term ‘forensic taphonomy’ was defined by Haglund and Sorg as “the study of postmortem processes which affect (1) the preservation, observation, or recovery of dead organisms, (2) the reconstruction of their biology or ecology, or (3) the reconstruction of the circumstances of their death (Haglund and Sorg, 1997b: 13). Because of the number of variables that potentially impact on human remains following death forensic taphonomy requires a multidisciplinary approach involving anthropology, pathology, entomology, botany, geology (including soil science), and/or marine biology (Sorg et al., 2012). While paleontology, archeology, and various forensic sciences have all incorporated taphonomic studies, one of the key differences is in timescale. In a forensic setting, the timescale between death and discovery is relatively short. Consequently, the study of taphonomy in a forensic setting includes a focus on both soft and hard tissue decomposition rates and patterns in addition to bone modification, disarticulation, and dispersal (Haglund and Sorg, 1997a).
Postmortem Processes Taphonomic processes begin at the point of death, as the body begins a series of physical, chemical, and biological processes termed decomposition. Generally, a body that is not preserved by freezing can reach one or a combination of three endpoints: (1) skeletonization; (2) mummification; or (3) adipocere formation. Autolysis involves the dynamic chemical breakdown of cellular functions and structures due to the loss of homeostasis (e.g., absence of oxygen, loss of thermoregulation, and pH control). The concomitant process of putrefaction includes the action of internal and external microorganisms, which utilize the body's nutrients to fuel their own physiology and reproduction. Both autolysis and putrefaction are profoundly influenced by temperature; freezing slows, or inhibits decomposition,
although it may itself produce cellular damage and degradation. As soft tissue decomposes and the chemical constituents are released into the environment, the body will skeletonize, exposing cartilage and bone tissue. The subsequent loss of organic substances within the bone has a much longer time frame, on average, than soft tissue loss. Bone in the living organism is composed of both organic and inorganic substances, and tends to retain its shape after death due to the underlying inorganic or mineral matrix (unless the environment is acidic). Minerals in the bones may be replaced chemically by minerals in the sediments, while maintaining the original shape of the bones, a process termed diagenesis. This occurs over long time periods (hundreds, potentially thousands of years), and leads to fossilization.
Variables That Affect the Preservation of Human Remains The factors affecting the preservation of human remains are numerous and variable, and the condition (and hence decomposition phase) may differ throughout the body, for example, the head versus the pelvic region, may show differential decomposition within the same individual. Intrinsic factors include:
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Body build (individual size and weight): thin bodies skeletonize more rapidly than more fleshy ones in the same conditions. Cadaver mass also plays a critical role in scavenging activity in an outdoor environment. Small cadavers (i.e., juveniles) can be carried away from the deposition site in their entirety to be consumed ex situ. Larger cadavers (i.e., adults) will typically be consumed in situ by one or more scavengers and it will take longer for the soft tissue to be removed from the bone. Age of the individual: Children's bones are smaller and less dense, and are, therefore, more prone to decay and faunal destruction (Manifold, 2012). In contrast, older people's bones may be affected by loss of bone density, thus making them more susceptible to decay. Additionally, the soft tissues of children contain a higher fat content, which may be conducive to adipocere formation under the appropriate taphonomic conditions (Mant, 1987). Elderly individuals often have significantly less fat content and body mass and soft tissue decomposition will, therefore, occur more rapidly compared to a healthy adult of average weight. Bone type and size (Henderson, 1987: 44–45): The variation in the morphology of bones mean that skeletal elements, such as the skull, as well as flat bones, such as the scapula and pelvis, are more prone
Anthropology: Taphonomy in the Forensic Context
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to warping and crushing in the burial environment. In contrast, tubular bones (such as the femur, fibula, tibia, humerus, radius, and ulna) are more resistant to soil pressure. Smaller bones, such as ear ossicles, the hyoid, and hand and foot phalanges are often missed during the recovery of human remains (Waldron, 1987), which means that there are limited data on their preservation characteristics. Disease and/or trauma: The degree of skeletal degradation and preservation can also be affected by antemortem diseases and perimortem trauma (Nawrocki, 1995). While it has been suggested that wounds can make the body more susceptible to invasion by extracorporeal organisms, Cross and Simmons (2010) found that trauma was not a major factor in the decomposition rate of pig carcasses, and that trauma sites on carcasses were not preferentially selected for oviposition by blow flies when compared with non-traumatized pig carcasses. Their study suggested that insects lay eggs preferentially in the natural orifices, regardless of trauma. However, there is yet to be a study conducted on the effect of major perimortem trauma (including fragmentation) on decomposition rate. Enteric microorganisms: Animals host a great diversity of microorganisms in most regions of the body during life including the skin, mouth, and gut. The microbial biomass in the gut has the greatest intrinsic impact on decomposition. It is responsible for the majority of putrefaction which transforms the body's macromolecules – carbohydrates, proteins, and lipids – into simpler compounds (Forbes, 2008). These microorganisms can alter the appearance, odor, and chemistry of decomposition. Extrinsic factors include:
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Time: between death and burial/disposal will affect how numerous other variables (see below) impact on preservation. Compared to paleontologists, forensic specialists deal with a much narrower time range. However, the length of time either buried in the ground or lying on the surface does not always directly correlate with better or worse survival of skeletal remains. Environment (geography and geology): ○ Topography: the presence of hills or valleys may create shade as well as slope (and therefore the potential for erosion and exposure of remains), water runoff or accumulation, which in turn impacts on temperature (see below). ○ Soil/sediment type: In the short term the soil type does not directly influence cadaveric decay. However, over a longer time period, soil type and pH significantly affects soft tissue and bone preservation Janaway, 1996. It is generally accepted that sandy soils with low moisture content
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will promote rapid loss of moisture from the body (known as desiccation) which promotes mummification in hot, arid climates. Heavy clay soils are also associated with an inhibition of decomposition resulting from the reducing conditions and retention of water which promote adipocere formation (Carter and Tibbett, 2008). In neutral (pH ¼7) or slightly alkaline (pH47) environments such as calcareous soils, skeletal preservation is relatively good. In more acidic environments (pHo7), the destruction of bone increases. However, preservation can differ considerably from one place to another. For example, many peat environments, although highly acidic, contain tannins and humic acid which cause tanning of soft tissue and lead to bone mineralization. Those tissues containing high levels of collagen and keratin are typically better preserved than the internal muscles and organs while the skeleton of the carcass will become extensively decalcified causing the dissolution and loss of bone structure (Micozzi, 1997; Janaway, 1996). Collagen fibers of the skin and other connective tissues are preserved through the process of tanning by polysaccharide sphagnan present in the peat. Keratinaceous materials, on the other hand, are likely preserved due to the exclusion of the microorganisms required to degrade keratin. ○ Water: humidity (or aridity), mean annual precipitation, groundwater (drainage) as well as aquatic environments (seas, lakes, rivers, and tidal zones) all have an impact on preservation (Beary and Lyman, 2012: 513–514). The presence of excess moisture facilitates saponification and the formation of adipocere. This is a waxy solidification of tissues that occurs with the build up of saturated fatty acids, and is a byproduct of autolysis and putrefaction. The formation of adipocere is, however, not restricted to water-logged locations (Forbes, 2008). Water is necessary for the survival of microorganisms that attack skeletal remains. Groundwater may also play a significant role in the chemical degradation of skeletal remains (Nielsen-Marsh, 2000). Bodies fully immersed in water may reduce to a skeleton within a week as a result of feeding activity of fish, crabs, and other aquatic animals (Petrik et al., 2004; Figure 1). In marine contexts, the presence of barnacles on human remains or associated clothing (e.g., shoes) can potentially be used by marine biologists to indicate a minimum postmortem interval (PMI) (Sorg et al., 1997). This requires knowledge about the specific species of barnacle in conjunction with information about the marine ecological context. Temperature: Differences in temperature may result from geographical environment (latitude), season
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and/or depth of burial. Temperature has been observed as “the most important driver for decomposition” (Sorg et al., 2012: 482; see also Megyesi et al., 2005) as it affects the rates of most chemical reactions, as well as the proliferation or retardation of microorganisms both within the body and the soil environment. For example, microorganisms are active in warmer soils because microbial activity doubles with each increase of 10 1C (up to 35–40 1C) (Carter and Tibbett, 2008). In contrast, dry sands aid preservation of soft tissue and bone because bacterial decomposition is retarded. Hot, dry climatic environments may result in desiccation of soft tissue, eventually resulting in mummification. The restriction of postmortem decomposition, resulting in mummification may occur in desert environments, as well as
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Figure 1 Drowning victim showing evidence of prolonged immersion, focal skeletonization, and evidence of postmortem marine feeding activity. Two days between last seen alive and autopsy (Image courtesy of the Victorian Institute of Forensic Medicine (VIFM)).
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in enclosed locations such as apartments or houses whereby the continuous heating during winter months can produce a hot, dry internal environment (Forbes, 2014b). Temperature also affects the extent of other biological activity. Enhanced enzymatic and microbial degradation promotes the accumulation and release of decomposition gases which attracts invertebrate and vertebrate scavengers to the remains. Flora and fauna: ○ Soil dwelling organisms: may include microorganisms such as fungi, bacteria, and algae that typically influence the chemical changes during decomposition. Microbes can invade bone, thus breaking down the collagen and producing acidic by-products which start to dissolve the bones mineral content. Meso-organisms, such as small worms, may also impact on the bone (Henderson, 1987). ○ Insects: play a significant role in the decomposition process through the consumption and dissolution of soft tissue (carrion eating), which results in skeletonization. Soft tissue decomposition is significantly faster in the presence of insects when compared to environments which restrict their access (e.g., buried, concealed, indoor, etc.) (Payne et al., 1968). ○ Macro fauna: including birds, fish, mammals, and invertebrate (especially insects and aquatic crustaceans) may all participate in scavenging and can influence the rate of decomposition (Sorg et al., 2012). This action may result in postdepositional movement of remains and/or scattering of bones, and in some cases significant destruction (carnivore chewing and/or rodent gnawing) of the remains. There are examples where scavenging and insect activity mimics changes resulting from true
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Figure 2 Parietal from Tomb E1, Jericho. (a) Section of human parietal fragment and (b) ectocranial view of same parietal fragment showing circular defects probably a result of insect activity (Images: S. Blau).
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pathology and/or trauma both in the soft tissue (Byard et al., 2006) and skeleton (e.g., Huchet et al., 2013; Figure 2). Vegetation: plant and root activity may damage skeletal remains by marking (staining) (Figure 3), warping (distorting), and physically and/or chemically degrading the surface of bones (exfoliation, etching, and/or staining) and/or integrity of the bone. However, it is also possible for there to be extensive vegetation present but no morphological change (Figure 4). Fire: The effects of heat on human remains include the destruction of soft tissue and may include changes in bone color, size (shrinkage), and cracking and warping (Beary and Lyman, 2012: 514–515) (Figure 5). The extent of macro and microscopic changes resulting from heat will depend on the length of time the remains were exposed to the heat and the temperatures reached during the burning period (Fairgrieve, 2014).
Other variables that affect the preservation of human remains are activities undertaken by humans. These may include:
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Figure 3 Superior view of human cranium showing differential staining as a result of partial submersion in water reeds. The lighter area was exposed (Image courtesy of VIFM).
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Body treatment: such as dismemberment through saw or knife cuts, embalming for burial or funeral purposes, wrapping (in plastic, carpet, sleeping bag, etc.), and/or burning prior to burial or disposal will also affect preservation (Sledzik and Micozzi, 1997). Clothing: may partially negate effects of general soil environment and delay decomposition, for example, by impeding access to scavengers. Clothing also retains moisture (depending on the fiber and soil type), which can promote preservation of the remains by adipocere formation. The presence of footwear or gloves can protect soft tissue for long periods, and following skeletonization, result in all bones of the feet or hands being recovered. Mode of disposal: inhumation, coffin burial, or cremation – in general, interred bodies decay slower than those on the surface because surface bodies are exposed to weathering and insect and scavenger activity. Coffins can prevent meso- and microorganisms from participating in cadaver decomposition, thus slowing the rate of soft tissue degradation. Type of coffin: wood, stone, lead, etc. also has an effect on preservation. For example, wood coffins often collapse and decay over time and retain water (Manifold, 2012: 59) (see above for effects), whereas lead coffins may lead to excellent preservation of the remains (Janaway, 1996). Burial depth: typically, the deeper the burial, the better preserved a body will be. This is because there are stable, low temperatures, reduced oxygen (which slows down the decomposition process), poor gas diffusion, and inaccessibility to floral and faunal agents of decay. This is in contrast to shallow graves where the body is covered with loosely compacted
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Figure 4 Anterior and left lateral view of human skull showing extensive root activity through the left orbit (eye socket) and maxilla (upper jaw) but no obvious distortion in morphology (shape) (Images: S. Blau).
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Figure 5 Differentially burnt human skeletal fragments juxtaposed to anatomical unburnt skeletal elements: (a) partial burnt right parietal, (b) complete unburnt right parietal, (c) partial burnt left glenoid, scapula, (d) complete unburnt left scapula, (e) partial burnt left mandibular ramus, and (f) complete unburnt mandible, left lateral view. (Images courtesy of the VIFM).
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soils that contain rocks or pebbles that can heat up. The temperature in such contexts is likely to fluctuate with the ambient temperature. Additionally, shallow burials may allow exposure of the remains through cracks that form on the soil surface as a result of bloating of the cadaver and subsequent depression of the grave soil. However, in deep burials soil pressure may distort bone, which has implications for aspects of forensic anthropology, such as skeletal measurements. Stewart (1979: 74) examined the remains of American war-dead which were recovered from shallow graves following the Korean War. He noted that they were virtually indistinguishable from prehistoric skeletons. Numbers of individuals buried: in cases of mass graves, differential preservation of bodies with the same PMI within the one grave has been observed. Mass graves may become anaerobic and the higher/ peripheral bodies will be skeletonized while the lower bodies retain soft tissue preservation. Bodies in close contact tend to be better preserved (Mant, 1987). Materials added to the burial: materials such as straw, wood shavings, vegetable matter, and lime
have been added to burials with the intention of either accelerating or delaying decomposition. Plant material is believed to accelerate decomposition through the introduction of additional bacteria into the decomposition environment (Carter and Tibbett, 2008). The intentional addition of lime (or lime-like substances, such as gypsum) to the burial environment also has a long history, with evidence of lime in burials recorded in many countries around the world, supposedly with the idea of preserving remains. In the forensic context, however, there are examples of cases where perpetrators have added lime to clandestine graves in the hope of accelerating decomposition and ultimately removing the remains altogether (Blau, 2008; Thew and Nawrocki, 2002). The confusion has occurred because there are, in fact, two types of lime: quicklime (CaO) and slaked lime (Ca(OH)2). The addition of slaked lime to a burial is thought to increase the pH to the extent that bacteria flora is destroyed and decomposition stops (Anonymous, 2008). Quicklime may also help preservation. It is well known that quicklime can be used to “to remove water from semisolid wastes” (Malone and May,
Anthropology: Taphonomy in the Forensic Context
1987: 42) and therefore may potentially dehydrate a body, resulting in some degree of preservation. Recent field studies using pig carcasses have demonstrated that both quicklime and slaked lime only slow decomposition in a burial, and that skeletonization is typically still the endpoint if sufficient time (in this study 42 months) passes (Schotsmans et al., 2012; Schotsmans, 2013).
Forensic Taphonomy In a forensic context, an understanding of taphonomy is important because of the potential impact preservation has on the investigative process. The main goals of forensic taphonomy are to:
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Estimate the time since death/PMI or time since deposition/post-burial interval. This estimation allows practitioners to determine whether human remains are of forensic or historical significance; Determine how the remains came to be where they were located or discovered; Determine what actions may have taken place to conceal the victim's identity or the entire crime; and Establish which factors have impacted on the remains, which in turn influence information that can be obtained from analyses (Beary and Lyman, 2012: 510), including injury interpretation. Specifically, the main interest is in differentiating perimortem trauma from postmortem changes (Ubelaker and Adams, 1995).
One of the main challenges in forensic taphonomy today is in understanding how postmortem changes to human remains will affect the estimation of time since death (Forbes, 2014a). Establishing the time since death (PMI) initially provides information about whether or not the case is actually of forensic significance. It is not uncommon for archeological human remains to be mistaken for forensically significant remains when first discovered due to their excellent preservation (e.g., in the case of the mummified remains of a man located on the Italian–Austrian border, the preservation of soft tissue was so good that it was at first believed the death was recent. It was only through dating the remains that it was demonstrated that the individual (referred to as ‘Ötzi – The Iceman’) was in fact among the oldest, and most well-preserved, natural mummies ever discovered (Forbes, 2014b). Obtaining information about the PMI can be gained through an analysis of the rates of soft tissue loss (e.g., Megyesi et al., 2005 who developed the first quantitative model of soft tissue decomposition). Insects, plants, fungi, and algae associated with human remains can also function as ‘biological clocks,’ and the chemical status of bones (e.g., loss of organic/inorganic phases, radiocarbon dating, bomb-pulse dating – Ubelaker et al.,
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2006), may also provide information on PMI (Sorg et al., 2012). Determining how the remains came to be where they were discovered requires a reconstruction of the circumstances before and after deposition based on a reconstruction of the scene itself (often referred to in taphonomic literature as site formation). Studies on selective preservation (i.e., the degree to which a sample of faunal remains represents the original population), and understanding transport and dispersal patterns are helpful for reconstructing the events. Discriminating between the products of human interaction and those created by physical, chemical, biological, and geological systems is also necessary (Haglund and Sorg, 1997a). Bone modification can result from numerous factors including perimortem trauma, scavenging, and diagenesis. Taphonomy is also vital for understanding preservation issues. In some cases poor preservation will impact the ability to identify a deceased person. Soft tissue decomposition may restrict a visual identification, thus resulting in the need for a scientific method of identification such as odontology, fingerprints, and/or DNA. In turn, an understanding of taphonomy is also important to attempt to predict DNA survival (e.g., Beary and Lyman, 2012: 512). Poor preservation may also restrict the anthropologist's ability to estimate variables such as the ancestry, sex, age, and stature (that is, a biological profile) (Ubelaker, 1997).
Research Trends in Taphonomy Experimental research both in laboratories and in the field continues to be undertaken on a wide range of subjects including: decomposition chemistry and its effects on the integrity of DNA; local microenvironmental features; forensic entomology; soil science; and mammalian and avian scavenging (see Sorg et al., 2012: 483–490 for an excellent summary).
Conclusion While attempts have been made to create ‘rules’ or models to predict and interpret preservation, the reality is that taphonomy is a complex process (Martin, 1999) and is influenced by the interaction of numerous intrinsic and extrinsic variables. Rather than one single factor, it is the interaction of the environment (geography and geology), water, soil, temperature and atmosphere, flora and fauna, and time and human activities that significantly impact on the preservation of human remains. For example, while a single variable such as clothing may impede decomposition, the condition of the body at the time of exhumation depends on the time between death and burial and length of
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deposition (Sorg et al., 2012). The complex nature of taphonomy is illustrated by cases where the PMI and burial type was the same, but there was variation in preservation between the different cases (Archer and Dodd, 2009: 391–392). Further, decomposition processes may vary at different locations within the same body, even within the same bone element, or among multiple bodies in the same depositional context. For example, soft tissue on extremities such as hands and feet may mummify, while the torso, having more soft tissue and moisture, skeletonizes. There are some basic processes associated with decomposition, but each forensic case will have its own unique characteristics, and therefore has to be assessed independently. In order to address important questions pertinent to a forensic investigation it is vital that both the death scene and the human remains themselves are examined. A description and assessment of the condition and preservation of the remains within the context of their deposition and/or discovery environment as well as microenvironmental variation provide a wealth of information necessary for a complete forensic investigation.
Acknowledgments The authors are grateful for comments provided by Melanie Archer.
See also: Animal Attacks and Injuries: Fatal. Animal Attacks and Injuries: Nonfatal. Anthropology: Ancestry Assessment. Anthropology: Bone Pathology and Antemortem Trauma. Anthropology: Cremated Bones − Anthropology. Anthropology: Forensic Anthropology and Childhood. Anthropology: Morphological Age Estimation. Anthropology: Overview. Anthropology: Role of DNA. Anthropology: Sex Determination. Anthropology: Stature Estimation from the Skeleton. Anthropology: Use of Forensic Archeology and Anthropology in the Search and Recovery of Buried Evidence. Death Investigation Systems: United States of America. Deaths: Trauma, Musculoskeletal System − Pathology. Healing and Repair of Wounds and Bones. Injury, Fatal and Nonfatal: Blunt Force Injury. Odontology: Overview. Postmortem Changes: Overview. War Crimes: Pathological Investigation. War Crimes: Site Investigation
References Anonymous, 2008. Carcass burial. Available at: http://www.netregs.gov.uk/netregs/ sectors/1447094/1447097/1727535/version=1Andlang=_e (accessed 08.07.08). Archer, M., Dodd, M., 2009. Medico-legal investigations of atrocities committed during the Solomon Islands “ethnic tensions”. In: Blau, S., Ubelaker, D.H. (Eds.), Handbook of Forensic Archeology and Anthropology. Walnut Creek, CA: Left Coast Press, pp. 388–396. Beary, M.O., Leary, R.L., 2012. The use of taphonomy in forensic anthropology: Past trends and future prospects. In: Dirkmaat, D.C. (Ed.), A Companion to Forensic Anthropology. Chichester: Wiley-Blackwell, pp. 499–527.
Behrensmeyer, A.K., 1978. Taphonomic and ecologic information from bone weathering. Paleobiology 4 (2), 150–162. Blau, S., 2008. In the limelight: A review of the use of lime in the disposal of bodies. Poster Presented at the 19th Australia and New Zealand Forensic Science Society Meeting, Melbourne. Blau, S., 2014. Taphonomy: Definition. In: Smith, C. (Ed.), Encyclopedia of Global Archeology. New York, NY: Springer, p. 7235. Byard, R.W., Gehl, A., Anders, S., Tsokos, M., 2006. Putrefaction and wound dehiscence: A potentially confusing postmortem phenomenon. American Journal of Forensic Medicine and Pathology 27 (1), 61–63. Cadee, G.C., 1991. The history of taphonomy. In: Donovan, S.K. (Ed.), The Processes of Fossilization. New York, NY: Columbia, pp. 3–12. Carter, D.O., Tibbett, M., 2008. Cadaver decomposition and soil. In: Tibbett, M., Carter, D.O. (Eds.), Soil Analysis in Forensic Taphonomy: Chemical and Biological Effects of Buried Human Remains. Boca Raton, FL: CRC Press, pp. 29–52. Cross, P., Simmons, T., 2010. The influence of penetrative trauma on the rate of decomposition. Journal of Forensic Sciences 55 (2), 295–301. Dirkmaat, D.C., Passacalcqua, N.V., 2012. Introduction to Part VI. In: Dirkmaat, D.C. (Ed.), A Companion to Forensic Anthropology. Chichester: Wiley-Blackwell, pp. 473–476. Efremov, I.A., 1940. Taphonomy: A new branch of paleontology. Pan-American Geologist 74, 81–93. Fairgrieve, S., 2014. Burned remains in forensic contexts. In: Smith, C. (Ed.), Encyclopedia of Global Archeology. New York, NY: Springer, pp. 1072–1077. Forbes, S., 2014a. Taphonomy in bioarchaeology and human osteology. In: Smith, C. (Ed.), Encyclopedia of Global Archeology. New York, NY: Springer, pp. 7219–7225. Forbes, S., 2014b. Time since death in bioarchaeology and human osteology. In: Smith, C. (Ed.), Encyclopedia of Global Archeology. New York, NY: Springer, pp. 7308–7312. Forbes, S.L., 2008. Decomposition chemistry in a burial environment. In: Tibbett, M., Carter, D.O. (Eds.), Soil Analysis in Forensic Taphonomy: Chemical and Biological Effects of Buried Human Remains. Boca Raton, FL: CRC Press, pp. 203–224. Haglund, W.D., Sorg, M.H., 1997a. Introduction to forensic taphonomy. In: Haglund, W.D., Sorg, M.H. (Eds.), Forensic Taphonomy: The Postmortem Fate of Human Remains. Boca Raton, FL: CRC Press, pp. 77–90. Haglund, W.D., Sorg, M.H., 1997b. Method and theory of forensic taphonomy research. In: Haglund, W.D., Sorg, M.H. (Eds.), Forensic Taphonomy: The Postmortem Fate of Human Remains. Boca Raton, FL: CRC Press, pp. 13–26. Henderson, J., 1987. Factors determining the state of preservation of human remains. In: Boddington, A., Garland, A.N., Janaway, R.C. (Eds.), Death, Decay and Destruction: Approaches to Archeology and Forensic Science. London: Manchester University Press, pp. 43–54. Huchet, J.-B., Le Mort, F., Rabinovich, R., et al., 2013. Identification of dermestid pupal chambers on Southern Levant human bones: Inference for reconstruction of Middle Bronze Age mortuary practices. Journal of Archeological Science 40 (10), 3793–3803. Janaway, R.C., 1996. The decay of buried human remains and their associated materials. In: Hunter, J., Roberts, C., Martin, A. (Eds.), Studies in Crime: An Introduction to Forensic Archeology. London: B. T. Batsford Ltd., pp. 58–85. Malone, P.G., May, J.H., 1987. Use of lime in the design of landfills for waste disposal. In: Gutschick, K.A. (Ed.), Lime for Environmental Uses ASTM STP 931. Philadelphia, PA: American Society for Testing and Materials, pp. 42–51. Manifold, B.M., 2012. Intrinsic and extrinsic factors involved in the preservation of non-adult skeletal remains in archeology and forensic science. Bulletin of the International Association for Paleodontology 6 (2), 51–69. Mant, A.K., 1987. Knowledge acquired from post-war exhumations. In: Boddington, A., Garland, A.N., Janaway, R. (Eds.), Death, Decay and Reconstruction: Approaches to Archeology and Forensic Science. London: Manchester University Press, pp. 10–21. Martin, R.E., 1999. Taphonomy: A Process Approach (Cambridge Paleobiology Series). Cambridge: Cambridge University Press. Megyesi, M.S., Nawrocki, S.P., Haskell, N.H., 2005. Using accumulated degree-days to estimate the postmortem interval from decomposed human remains. Journal of Forensic Sciences 50 (3), 618–626. Micozzi, M.S., 1997. Frozen environments and soft tissue preservation. In: Haglund, W.D., Sorg, M.H. (Eds.), Forensic Taphonomy: The Postmortem Fate of Human Remains. Boca Raton, FL: CRC Press, pp. 171–180.
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Nawrocki, S.P., 1995. Taphonomic processes in historic cemeteries. In: Grauer, A.L. (Ed.), Bodies of Evidence: Reconstructing History through Skeletal Analysis. New York, NY: Wiley-Liss, pp. 49–66. Nawrocki, S.P., 2009. Forensic taphonomy. In: Blau, S., Ubelaker, D.H. (Eds.), Handbook of Forensic Archeology and Anthropology. Walnut Creek, CA: Left Coast Press, pp. 284–294. Nielsen-Marsh, C., 2000. The chemical degradation of bones. In: Cox, M., Mays, S. (Eds.), Human Osteology in Archeology and Forensic Science. London: Greenwich Medical Media, pp. 439–451. Payne, J.A., King, E.W., Beinhart, G., 1968. Arthropod succession and decomposition of buried pigs. Nature 219, 1180–1181. Petrik, M.S., Hobishchak, N.R., Anderson, G.S., 2004. Examination of factors surrounding human decomposition in freshwater. A review of body recoveries and Coroner cases in British Columbia. Canadian Society of Forensic Science 37 (1), 9–17. Schotsmans, E.M., Denton, J., Dekeirsschieter, J., et al., 2012. Effects of hydrated lime and quicklime on the decay of buried human remains using pig cadavers as human body analogues. Forensic Science International 217 (1−3), 50–59. Schotsmans, E.M.J., 2013. The Effects of Lime on the Decomposition of Buried Human Remains: A Field and Laboratory Based Study for Forensic and Archeological Application. (PhD Thesis). UK: University of Bradford (Unpublished). Sledzik, P.S., Micozzi., M.S., 1997. Autopsied, embalmed, and preserved human remains: Distinguishing features in forensic and historic contexts. In: Haglund, W.D., Sorg, M.H. (Eds.), Forensic Taphonomy: The Postmortem Fate of Human Remains. Boca Raton, FL: CRC Press, pp. 77–90. Sorg, M.H., Dearborn, J.H., Monahan, E.I., et al., 1997. Forensic taphonpmy in marine contexts. In: Haglund, W.D., Sorg, M.H. (Eds.), Forensic Taphonomy: The Postmortem Fate of Human Remains. Boca Raton, FL: CRC Press, pp. 567–604. Sorg, M.H., Haglund, W.D., Wren, J.A., 2012. Current research in forensic taphonomy. In: Dirkmaat, D.C. (Ed.), A Companion to Forensic Anthropology. Chichester: Wiley-Blackwell, pp. 477–498. Stewart, T.D., 1979. Essentials of Forensic Anthropology. Springfield, IL: Charles C. Thomas. Thew, H.A., Nawrocki, S.P., 2002. The effects of lime on the decomposition rate of buried remains (abstract). Proceedings of the 54th Annual Meeting of the
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American Academy of Forensic Sciences. February 11−16, Atlanta, GA, p. 237. Abstract H45. Ubelaker, D.H., 1997. Taphonomic applications in forensic anthropology. In: Haglund, W.D., Sorg, M.H. (Eds.), Forensic Taphonomy: The Postmortem Fate of Human Remains. Boca Raton, FL: CRC Press, pp. 77–90. Ubelaker, D.H., Adams, B.J., 1995. Differentiation of perimortem and postmortem trauma using taphonomic indictors. Journal of Forensic Sciences 40, 509–512. Ubelaker, D.H., Buchholz, B.A., Stewart, J.E.B., 2006. Analysis of artificial radiocarbon in different skeletal and dental tissue types to evaluate date of death. Journal of Forensic Sciences 51 (3), 484–488. Waldron, T., 1987. The relative survival of the human skeleton: Implications for paleopathology. In: Boddington, A., Garland, A.N., Janaway, R.C. (Eds.), Death, Decay and Reconstruction: Approaches to Archeology and Forensic Science. Manchester: Manchester University Press, pp. 55–64. Weigelt, J., 1989. Recent Vertebrate Carcasses and Their Paleobiological Implications (J. Schaefer, Trans.). Chicago, IL: University of Chicago Press. [Translation of Rezente Wirbeltierleichen und ihre Palaobiologische Bedeutung, 1927].
Further Reading Allison, P.A., Briggs, D.E.G., 1991. Taphonomy: Releasing the Data Locked in the Fossil Record, vol. 9. New York, NY: Plenum Press. Haglund, W.D., Sorg, M.H., 1997. Advances in Forensic Taphonomy: Method, Theory, and Archeological Perspectives. Boca Raton, FL: CRC Press. Lyman, R.L., 1994. Vertebrate Taphonomy. Cambridge: Cambridge University Press. Mann, R.W., Bass, W.M., Meadows, L., 1990. Time since death and decomposition of the human body: Variables and observations in case and experimental field studies. Journal of Forensic Sciences 35 (1), 103–111. Shipman, P., 1981. Life History of a Fossil: An Introduction to Taphonomy and Paleoecology. Cambridge: Harvard University Press. Wells, C., 1967. Pseudopathology. In: Brothwell, D., Sandison, A.T. (Eds.), Diseases in Antiquity. Springfield, IL: Thomas, pp. 5–19.
Abstract This chapter defines the term ‘taphonomy’ and summarizes the history of the study as pursued in various disciplines. Intrinsic and extrinsic variables that affect preservation of human remains are summarized. This is followed by an examination of the questions that forensic taphonomy can potentially address, including: what is the estimated time since death/postmortem interval or time since deposition/post-burial interval?; how did the remains come to be where they were located or discovered?; what actions may have taken place to conceal the victim’s identity or the crime?; and which factors effect injury interpretation, specifically, differentiating perimortem trauma from postmortem changes?
Glossary Adipocere formation The chemical conversion of adipose tissue into a solid substance comprising predominantly saturated fatty acids. Autolysis Enzymatic degradation of cells or tissues. Biomass Biological material derived from living or recently living organisms. Biostratinomy The sedimentary history of a fossil from death to the final burial. Diagenesis Chemical and physical alteration of sediments during rock formation.
Introduction The term taphonomy originates from the Greek taphos – τάφος (meaning burial), and nomos – νόμος (meaning law), and is defined as the study of the transition of plant and animal organisms after death from the biosphere (living surfaces) to the lithosphere (underground) (Blau, 2014). Taphonomists study environmental and anthropogenic actions and processes (both cultural and individual) that affect the remains of biological organisms from the time of death to discovery (Nawrocki, 2009). Taphonomy was first defined by the Russian paleontologist, Efremov (1940), although the science of taphonomy had been practiced for centuries preceding this definition (Cadee, 1991). Taphonomic studies were traditionally the focus of paleontologists who were interested in understanding the processes of fossilization from death to diagenesis (Martin, 1999). Weigelt (1927; translated in 1989) provided one of the most thorough descriptions of decomposition, including transport of remains, and burial of carcasses on the edge of a lake in
Encyclopedia of Forensic and Legal Medicine, Volume 1
Disarticulation A separation at the joints. Microorganisms A microscopic organism such as bacteria or fungus. Mummification The rapid loss of moisture from soft tissue through the process of desiccation. pH It is a measure of the acidity of an aqueous solution. Soil pH is measured on a logarithmic scale and is determined by the concentration of hydrogen ions. Putrefaction Microbial degradation of cells or tissues.
the US Gulf Coast following a massive mortality of cattle due to severe climatic conditions. His study was the first investigation to thoroughly document the sedimentary history of fossils from death to decomposition (necrolysis) through to the final burial; these processes are referred to as biostratinomy. During the 1970s, paleoanthropologists and archeologists “began to study taphonomy in order to determine how and why floral and faunal remains accumulated and differentially preserved within the archeological record” (Forbes, 2014a). Archeologists examine both natural and human induced (cultural) processes. Studies include bone modification by scavenger species, and butchering modification by modern hunter–gatherer people in order to differentiate the taphonomic signatures of nonhuman scavengers from that of human cultural food preparation. Models of bone weathering have been developed and experiments devised to simulate the effects of transportation by rivers on different types of bones (e.g., Behrensmeyer, 1978). Some scientists have observed particular species or environmental processes as they occur in nature while
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others have performed actualistic or experimental research. These efforts produced models that could be applied to archeological and forensic cases (see Beary and Lyman, 2012 for a history of taphonomy research). In the 1980s, taphonomic approaches were adopted by several of the forensic sciences because of the value the discipline added to understanding what happens to a body from the time immediately after death to the point of recovery. This included excavation, post-recovery transport (Beary and Lyman, 2012: 517–518), autopsy examination and other forensic analyses (Dirkmaat and Passacalcqua, 2012). Specifically, researchers were most interested in estimating time since death, reconstructing the events surrounding death and pre- and post-burial, and discriminating between bone modifications resulting from human behavior and those caused by taphonomic factors (Haglund and Sorg, 1997a; Ubelaker, 1997). The term ‘forensic taphonomy’ was defined by Haglund and Sorg as “the study of postmortem processes which affect (1) the preservation, observation, or recovery of dead organisms, (2) the reconstruction of their biology or ecology, or (3) the reconstruction of the circumstances of their death (Haglund and Sorg, 1997b: 13). Because of the number of variables that potentially impact on human remains following death forensic taphonomy requires a multidisciplinary approach involving anthropology, pathology, entomology, botany, geology (including soil science), and/or marine biology (Sorg et al., 2012). While paleontology, archeology, and various forensic sciences have all incorporated taphonomic studies, one of the key differences is in timescale. In a forensic setting, the timescale between death and discovery is relatively short. Consequently, the study of taphonomy in a forensic setting includes a focus on both soft and hard tissue decomposition rates and patterns in addition to bone modification, disarticulation, and dispersal (Haglund and Sorg, 1997a).
Postmortem Processes Taphonomic processes begin at the point of death, as the body begins a series of physical, chemical, and biological processes termed decomposition. Generally, a body that is not preserved by freezing can reach one or a combination of three endpoints: (1) skeletonization; (2) mummification; or (3) adipocere formation. Autolysis involves the dynamic chemical breakdown of cellular functions and structures due to the loss of homeostasis (e.g., absence of oxygen, loss of thermoregulation, and pH control). The concomitant process of putrefaction includes the action of internal and external microorganisms, which utilize the body's nutrients to fuel their own physiology and reproduction. Both autolysis and putrefaction are profoundly influenced by temperature; freezing slows, or inhibits decomposition,
although it may itself produce cellular damage and degradation. As soft tissue decomposes and the chemical constituents are released into the environment, the body will skeletonize, exposing cartilage and bone tissue. The subsequent loss of organic substances within the bone has a much longer time frame, on average, than soft tissue loss. Bone in the living organism is composed of both organic and inorganic substances, and tends to retain its shape after death due to the underlying inorganic or mineral matrix (unless the environment is acidic). Minerals in the bones may be replaced chemically by minerals in the sediments, while maintaining the original shape of the bones, a process termed diagenesis. This occurs over long time periods (hundreds, potentially thousands of years), and leads to fossilization.
Variables That Affect the Preservation of Human Remains The factors affecting the preservation of human remains are numerous and variable, and the condition (and hence decomposition phase) may differ throughout the body, for example, the head versus the pelvic region, may show differential decomposition within the same individual. Intrinsic factors include:
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Body build (individual size and weight): thin bodies skeletonize more rapidly than more fleshy ones in the same conditions. Cadaver mass also plays a critical role in scavenging activity in an outdoor environment. Small cadavers (i.e., juveniles) can be carried away from the deposition site in their entirety to be consumed ex situ. Larger cadavers (i.e., adults) will typically be consumed in situ by one or more scavengers and it will take longer for the soft tissue to be removed from the bone. Age of the individual: Children's bones are smaller and less dense, and are, therefore, more prone to decay and faunal destruction (Manifold, 2012). In contrast, older people's bones may be affected by loss of bone density, thus making them more susceptible to decay. Additionally, the soft tissues of children contain a higher fat content, which may be conducive to adipocere formation under the appropriate taphonomic conditions (Mant, 1987). Elderly individuals often have significantly less fat content and body mass and soft tissue decomposition will, therefore, occur more rapidly compared to a healthy adult of average weight. Bone type and size (Henderson, 1987: 44–45): The variation in the morphology of bones mean that skeletal elements, such as the skull, as well as flat bones, such as the scapula and pelvis, are more prone
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to warping and crushing in the burial environment. In contrast, tubular bones (such as the femur, fibula, tibia, humerus, radius, and ulna) are more resistant to soil pressure. Smaller bones, such as ear ossicles, the hyoid, and hand and foot phalanges are often missed during the recovery of human remains (Waldron, 1987), which means that there are limited data on their preservation characteristics. Disease and/or trauma: The degree of skeletal degradation and preservation can also be affected by antemortem diseases and perimortem trauma (Nawrocki, 1995). While it has been suggested that wounds can make the body more susceptible to invasion by extracorporeal organisms, Cross and Simmons (2010) found that trauma was not a major factor in the decomposition rate of pig carcasses, and that trauma sites on carcasses were not preferentially selected for oviposition by blow flies when compared with non-traumatized pig carcasses. Their study suggested that insects lay eggs preferentially in the natural orifices, regardless of trauma. However, there is yet to be a study conducted on the effect of major perimortem trauma (including fragmentation) on decomposition rate. Enteric microorganisms: Animals host a great diversity of microorganisms in most regions of the body during life including the skin, mouth, and gut. The microbial biomass in the gut has the greatest intrinsic impact on decomposition. It is responsible for the majority of putrefaction which transforms the body's macromolecules – carbohydrates, proteins, and lipids – into simpler compounds (Forbes, 2008). These microorganisms can alter the appearance, odor, and chemistry of decomposition. Extrinsic factors include:
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Time: between death and burial/disposal will affect how numerous other variables (see below) impact on preservation. Compared to paleontologists, forensic specialists deal with a much narrower time range. However, the length of time either buried in the ground or lying on the surface does not always directly correlate with better or worse survival of skeletal remains. Environment (geography and geology): ○ Topography: the presence of hills or valleys may create shade as well as slope (and therefore the potential for erosion and exposure of remains), water runoff or accumulation, which in turn impacts on temperature (see below). ○ Soil/sediment type: In the short term the soil type does not directly influence cadaveric decay. However, over a longer time period, soil type and pH significantly affects soft tissue and bone preservation Janaway, 1996. It is generally accepted that sandy soils with low moisture content
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will promote rapid loss of moisture from the body (known as desiccation) which promotes mummification in hot, arid climates. Heavy clay soils are also associated with an inhibition of decomposition resulting from the reducing conditions and retention of water which promote adipocere formation (Carter and Tibbett, 2008). In neutral (pH ¼7) or slightly alkaline (pH47) environments such as calcareous soils, skeletal preservation is relatively good. In more acidic environments (pHo7), the destruction of bone increases. However, preservation can differ considerably from one place to another. For example, many peat environments, although highly acidic, contain tannins and humic acid which cause tanning of soft tissue and lead to bone mineralization. Those tissues containing high levels of collagen and keratin are typically better preserved than the internal muscles and organs while the skeleton of the carcass will become extensively decalcified causing the dissolution and loss of bone structure (Micozzi, 1997; Janaway, 1996). Collagen fibers of the skin and other connective tissues are preserved through the process of tanning by polysaccharide sphagnan present in the peat. Keratinaceous materials, on the other hand, are likely preserved due to the exclusion of the microorganisms required to degrade keratin. ○ Water: humidity (or aridity), mean annual precipitation, groundwater (drainage) as well as aquatic environments (seas, lakes, rivers, and tidal zones) all have an impact on preservation (Beary and Lyman, 2012: 513–514). The presence of excess moisture facilitates saponification and the formation of adipocere. This is a waxy solidification of tissues that occurs with the build up of saturated fatty acids, and is a byproduct of autolysis and putrefaction. The formation of adipocere is, however, not restricted to water-logged locations (Forbes, 2008). Water is necessary for the survival of microorganisms that attack skeletal remains. Groundwater may also play a significant role in the chemical degradation of skeletal remains (Nielsen-Marsh, 2000). Bodies fully immersed in water may reduce to a skeleton within a week as a result of feeding activity of fish, crabs, and other aquatic animals (Petrik et al., 2004; Figure 1). In marine contexts, the presence of barnacles on human remains or associated clothing (e.g., shoes) can potentially be used by marine biologists to indicate a minimum postmortem interval (PMI) (Sorg et al., 1997). This requires knowledge about the specific species of barnacle in conjunction with information about the marine ecological context. Temperature: Differences in temperature may result from geographical environment (latitude), season
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and/or depth of burial. Temperature has been observed as “the most important driver for decomposition” (Sorg et al., 2012: 482; see also Megyesi et al., 2005) as it affects the rates of most chemical reactions, as well as the proliferation or retardation of microorganisms both within the body and the soil environment. For example, microorganisms are active in warmer soils because microbial activity doubles with each increase of 10 1C (up to 35–40 1C) (Carter and Tibbett, 2008). In contrast, dry sands aid preservation of soft tissue and bone because bacterial decomposition is retarded. Hot, dry climatic environments may result in desiccation of soft tissue, eventually resulting in mummification. The restriction of postmortem decomposition, resulting in mummification may occur in desert environments, as well as
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Figure 1 Drowning victim showing evidence of prolonged immersion, focal skeletonization, and evidence of postmortem marine feeding activity. Two days between last seen alive and autopsy (Image courtesy of the Victorian Institute of Forensic Medicine (VIFM)).
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in enclosed locations such as apartments or houses whereby the continuous heating during winter months can produce a hot, dry internal environment (Forbes, 2014b). Temperature also affects the extent of other biological activity. Enhanced enzymatic and microbial degradation promotes the accumulation and release of decomposition gases which attracts invertebrate and vertebrate scavengers to the remains. Flora and fauna: ○ Soil dwelling organisms: may include microorganisms such as fungi, bacteria, and algae that typically influence the chemical changes during decomposition. Microbes can invade bone, thus breaking down the collagen and producing acidic by-products which start to dissolve the bones mineral content. Meso-organisms, such as small worms, may also impact on the bone (Henderson, 1987). ○ Insects: play a significant role in the decomposition process through the consumption and dissolution of soft tissue (carrion eating), which results in skeletonization. Soft tissue decomposition is significantly faster in the presence of insects when compared to environments which restrict their access (e.g., buried, concealed, indoor, etc.) (Payne et al., 1968). ○ Macro fauna: including birds, fish, mammals, and invertebrate (especially insects and aquatic crustaceans) may all participate in scavenging and can influence the rate of decomposition (Sorg et al., 2012). This action may result in postdepositional movement of remains and/or scattering of bones, and in some cases significant destruction (carnivore chewing and/or rodent gnawing) of the remains. There are examples where scavenging and insect activity mimics changes resulting from true
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Figure 2 Parietal from Tomb E1, Jericho. (a) Section of human parietal fragment and (b) ectocranial view of same parietal fragment showing circular defects probably a result of insect activity (Images: S. Blau).
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pathology and/or trauma both in the soft tissue (Byard et al., 2006) and skeleton (e.g., Huchet et al., 2013; Figure 2). Vegetation: plant and root activity may damage skeletal remains by marking (staining) (Figure 3), warping (distorting), and physically and/or chemically degrading the surface of bones (exfoliation, etching, and/or staining) and/or integrity of the bone. However, it is also possible for there to be extensive vegetation present but no morphological change (Figure 4). Fire: The effects of heat on human remains include the destruction of soft tissue and may include changes in bone color, size (shrinkage), and cracking and warping (Beary and Lyman, 2012: 514–515) (Figure 5). The extent of macro and microscopic changes resulting from heat will depend on the length of time the remains were exposed to the heat and the temperatures reached during the burning period (Fairgrieve, 2014).
Other variables that affect the preservation of human remains are activities undertaken by humans. These may include:
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Figure 3 Superior view of human cranium showing differential staining as a result of partial submersion in water reeds. The lighter area was exposed (Image courtesy of VIFM).
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Body treatment: such as dismemberment through saw or knife cuts, embalming for burial or funeral purposes, wrapping (in plastic, carpet, sleeping bag, etc.), and/or burning prior to burial or disposal will also affect preservation (Sledzik and Micozzi, 1997). Clothing: may partially negate effects of general soil environment and delay decomposition, for example, by impeding access to scavengers. Clothing also retains moisture (depending on the fiber and soil type), which can promote preservation of the remains by adipocere formation. The presence of footwear or gloves can protect soft tissue for long periods, and following skeletonization, result in all bones of the feet or hands being recovered. Mode of disposal: inhumation, coffin burial, or cremation – in general, interred bodies decay slower than those on the surface because surface bodies are exposed to weathering and insect and scavenger activity. Coffins can prevent meso- and microorganisms from participating in cadaver decomposition, thus slowing the rate of soft tissue degradation. Type of coffin: wood, stone, lead, etc. also has an effect on preservation. For example, wood coffins often collapse and decay over time and retain water (Manifold, 2012: 59) (see above for effects), whereas lead coffins may lead to excellent preservation of the remains (Janaway, 1996). Burial depth: typically, the deeper the burial, the better preserved a body will be. This is because there are stable, low temperatures, reduced oxygen (which slows down the decomposition process), poor gas diffusion, and inaccessibility to floral and faunal agents of decay. This is in contrast to shallow graves where the body is covered with loosely compacted
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Figure 4 Anterior and left lateral view of human skull showing extensive root activity through the left orbit (eye socket) and maxilla (upper jaw) but no obvious distortion in morphology (shape) (Images: S. Blau).
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Figure 5 Differentially burnt human skeletal fragments juxtaposed to anatomical unburnt skeletal elements: (a) partial burnt right parietal, (b) complete unburnt right parietal, (c) partial burnt left glenoid, scapula, (d) complete unburnt left scapula, (e) partial burnt left mandibular ramus, and (f) complete unburnt mandible, left lateral view. (Images courtesy of the VIFM).
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soils that contain rocks or pebbles that can heat up. The temperature in such contexts is likely to fluctuate with the ambient temperature. Additionally, shallow burials may allow exposure of the remains through cracks that form on the soil surface as a result of bloating of the cadaver and subsequent depression of the grave soil. However, in deep burials soil pressure may distort bone, which has implications for aspects of forensic anthropology, such as skeletal measurements. Stewart (1979: 74) examined the remains of American war-dead which were recovered from shallow graves following the Korean War. He noted that they were virtually indistinguishable from prehistoric skeletons. Numbers of individuals buried: in cases of mass graves, differential preservation of bodies with the same PMI within the one grave has been observed. Mass graves may become anaerobic and the higher/ peripheral bodies will be skeletonized while the lower bodies retain soft tissue preservation. Bodies in close contact tend to be better preserved (Mant, 1987). Materials added to the burial: materials such as straw, wood shavings, vegetable matter, and lime
have been added to burials with the intention of either accelerating or delaying decomposition. Plant material is believed to accelerate decomposition through the introduction of additional bacteria into the decomposition environment (Carter and Tibbett, 2008). The intentional addition of lime (or lime-like substances, such as gypsum) to the burial environment also has a long history, with evidence of lime in burials recorded in many countries around the world, supposedly with the idea of preserving remains. In the forensic context, however, there are examples of cases where perpetrators have added lime to clandestine graves in the hope of accelerating decomposition and ultimately removing the remains altogether (Blau, 2008; Thew and Nawrocki, 2002). The confusion has occurred because there are, in fact, two types of lime: quicklime (CaO) and slaked lime (Ca(OH)2). The addition of slaked lime to a burial is thought to increase the pH to the extent that bacteria flora is destroyed and decomposition stops (Anonymous, 2008). Quicklime may also help preservation. It is well known that quicklime can be used to “to remove water from semisolid wastes” (Malone and May,
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1987: 42) and therefore may potentially dehydrate a body, resulting in some degree of preservation. Recent field studies using pig carcasses have demonstrated that both quicklime and slaked lime only slow decomposition in a burial, and that skeletonization is typically still the endpoint if sufficient time (in this study 42 months) passes (Schotsmans et al., 2012; Schotsmans, 2013).
Forensic Taphonomy In a forensic context, an understanding of taphonomy is important because of the potential impact preservation has on the investigative process. The main goals of forensic taphonomy are to:
•
• • •
Estimate the time since death/PMI or time since deposition/post-burial interval. This estimation allows practitioners to determine whether human remains are of forensic or historical significance; Determine how the remains came to be where they were located or discovered; Determine what actions may have taken place to conceal the victim's identity or the entire crime; and Establish which factors have impacted on the remains, which in turn influence information that can be obtained from analyses (Beary and Lyman, 2012: 510), including injury interpretation. Specifically, the main interest is in differentiating perimortem trauma from postmortem changes (Ubelaker and Adams, 1995).
One of the main challenges in forensic taphonomy today is in understanding how postmortem changes to human remains will affect the estimation of time since death (Forbes, 2014a). Establishing the time since death (PMI) initially provides information about whether or not the case is actually of forensic significance. It is not uncommon for archeological human remains to be mistaken for forensically significant remains when first discovered due to their excellent preservation (e.g., in the case of the mummified remains of a man located on the Italian–Austrian border, the preservation of soft tissue was so good that it was at first believed the death was recent. It was only through dating the remains that it was demonstrated that the individual (referred to as ‘Ötzi – The Iceman’) was in fact among the oldest, and most well-preserved, natural mummies ever discovered (Forbes, 2014b). Obtaining information about the PMI can be gained through an analysis of the rates of soft tissue loss (e.g., Megyesi et al., 2005 who developed the first quantitative model of soft tissue decomposition). Insects, plants, fungi, and algae associated with human remains can also function as ‘biological clocks,’ and the chemical status of bones (e.g., loss of organic/inorganic phases, radiocarbon dating, bomb-pulse dating – Ubelaker et al.,
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2006), may also provide information on PMI (Sorg et al., 2012). Determining how the remains came to be where they were discovered requires a reconstruction of the circumstances before and after deposition based on a reconstruction of the scene itself (often referred to in taphonomic literature as site formation). Studies on selective preservation (i.e., the degree to which a sample of faunal remains represents the original population), and understanding transport and dispersal patterns are helpful for reconstructing the events. Discriminating between the products of human interaction and those created by physical, chemical, biological, and geological systems is also necessary (Haglund and Sorg, 1997a). Bone modification can result from numerous factors including perimortem trauma, scavenging, and diagenesis. Taphonomy is also vital for understanding preservation issues. In some cases poor preservation will impact the ability to identify a deceased person. Soft tissue decomposition may restrict a visual identification, thus resulting in the need for a scientific method of identification such as odontology, fingerprints, and/or DNA. In turn, an understanding of taphonomy is also important to attempt to predict DNA survival (e.g., Beary and Lyman, 2012: 512). Poor preservation may also restrict the anthropologist's ability to estimate variables such as the ancestry, sex, age, and stature (that is, a biological profile) (Ubelaker, 1997).
Research Trends in Taphonomy Experimental research both in laboratories and in the field continues to be undertaken on a wide range of subjects including: decomposition chemistry and its effects on the integrity of DNA; local microenvironmental features; forensic entomology; soil science; and mammalian and avian scavenging (see Sorg et al., 2012: 483–490 for an excellent summary).
Conclusion While attempts have been made to create ‘rules’ or models to predict and interpret preservation, the reality is that taphonomy is a complex process (Martin, 1999) and is influenced by the interaction of numerous intrinsic and extrinsic variables. Rather than one single factor, it is the interaction of the environment (geography and geology), water, soil, temperature and atmosphere, flora and fauna, and time and human activities that significantly impact on the preservation of human remains. For example, while a single variable such as clothing may impede decomposition, the condition of the body at the time of exhumation depends on the time between death and burial and length of
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deposition (Sorg et al., 2012). The complex nature of taphonomy is illustrated by cases where the PMI and burial type was the same, but there was variation in preservation between the different cases (Archer and Dodd, 2009: 391–392). Further, decomposition processes may vary at different locations within the same body, even within the same bone element, or among multiple bodies in the same depositional context. For example, soft tissue on extremities such as hands and feet may mummify, while the torso, having more soft tissue and moisture, skeletonizes. There are some basic processes associated with decomposition, but each forensic case will have its own unique characteristics, and therefore has to be assessed independently. In order to address important questions pertinent to a forensic investigation it is vital that both the death scene and the human remains themselves are examined. A description and assessment of the condition and preservation of the remains within the context of their deposition and/or discovery environment as well as microenvironmental variation provide a wealth of information necessary for a complete forensic investigation.
Acknowledgments The authors are grateful for comments provided by Melanie Archer.
See also: Animal Attacks and Injuries: Fatal. Animal Attacks and Injuries: Nonfatal. Anthropology: Ancestry Assessment. Anthropology: Bone Pathology and Antemortem Trauma. Anthropology: Cremated Bones − Anthropology. Anthropology: Forensic Anthropology and Childhood. Anthropology: Morphological Age Estimation. Anthropology: Overview. Anthropology: Role of DNA. Anthropology: Sex Determination. Anthropology: Stature Estimation from the Skeleton. Anthropology: Use of Forensic Archeology and Anthropology in the Search and Recovery of Buried Evidence. Death Investigation Systems: United States of America. Deaths: Trauma, Musculoskeletal System − Pathology. Healing and Repair of Wounds and Bones. Injury, Fatal and Nonfatal: Blunt Force Injury. Odontology: Overview. Postmortem Changes: Overview. War Crimes: Pathological Investigation. War Crimes: Site Investigation
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Further Reading Allison, P.A., Briggs, D.E.G., 1991. Taphonomy: Releasing the Data Locked in the Fossil Record, vol. 9. New York, NY: Plenum Press. Haglund, W.D., Sorg, M.H., 1997. Advances in Forensic Taphonomy: Method, Theory, and Archeological Perspectives. Boca Raton, FL: CRC Press. Lyman, R.L., 1994. Vertebrate Taphonomy. Cambridge: Cambridge University Press. Mann, R.W., Bass, W.M., Meadows, L., 1990. Time since death and decomposition of the human body: Variables and observations in case and experimental field studies. Journal of Forensic Sciences 35 (1), 103–111. Shipman, P., 1981. Life History of a Fossil: An Introduction to Taphonomy and Paleoecology. Cambridge: Harvard University Press. Wells, C., 1967. Pseudopathology. In: Brothwell, D., Sandison, A.T. (Eds.), Diseases in Antiquity. Springfield, IL: Thomas, pp. 5–19.