Taphonomy
Taphonomy is the scientific study that examines the postmortem changes that occur in organisms from the time of death until their discovery. This field of research is particularly significant in understanding how decomposing human remains can be altered by environmental factors, which may complicate forensic investigations by mimicking signs of trauma. The term was first coined in 1940 by Russian paleontologist Ivan Yefremov, originally referring to the "laws of burial." Since the 1980s, taphonomy has gained prominence in forensic science, leading to a specialization known as forensic taphonomy, which focuses on human decomposition and time since death (TSD) estimations.
Forensic taphonomists, including anthropologists and entomologists, study the stages of decomposition—fresh, bloat, active decay, advanced decay, and skeletal stages—to gather clues about the time elapsed since death. Various factors, such as temperature and humidity, significantly influence the rate of decay, and the process is impacted by biological agents like insects and scavengers. Understanding these changes is essential, as postmortem alterations can sometimes be confused with perimortem trauma, necessitating a careful distinction between the two. Taphonomic studies often require interdisciplinary collaboration across fields like anthropology, pathology, and soil science, enhancing the understanding of how remains decompose and aiding in criminal investigations.
Subject Terms
Taphonomy
DEFINITION: Study of postmortem changes in organisms from the time of death to the point of discovery.
SIGNIFICANCE: Postmortem events alter the condition of human remains and may leave evidence that can potentially be confused with trauma. The study of human decomposition also provides important clues that aid in the estimation of the time since death.
The term “taphonomy” was coined in 1940 by the Russian paleontologist Ivan Yefremov to describe the “laws of burial.” Taphonomists attempt to understand events that occur to organisms after death, a period defined as the postmortem interval. Early research in the field of taphonomy focused on the study of fossils, especially the conditions that determine how and why certain organisms are preserved in the fossil record. Since the 1980s, taphonomy has become an important research area in forensic science, focusing on the study of postmortem changes in human remains and estimation of the time since death (TSD), also known as the postmortem interval. This emerging field, known as forensic taphonomy, applies the principles of taphonomy to the study of human decomposition. TSD studies are usually undertaken by anthropologists, entomologists, or pathologists who have forensic expertise, but the examination of postmortem changes in human remains is an interdisciplinary study and may involve a number of different specialists.
Goals of Forensic Taphonomy
Forensic taphonomy addresses several important medicolegal issues, including estimation of the TSD and the study of postmortem changes in human remains caused by decomposition, transport, weathering, or fire. TSD estimation can aid in narrowing down the search for a missing person or can be used to exclude potential suspects from consideration who have alibis for the time when an alleged occurred.
When a corpse is exposed to the environment for a long period of time, estimation of the TSD becomes increasingly difficult. Over time, insects, bacteria, plants, animal scavengers, and other aspects of the physical environment alter remains. Postmortem changes to remains can potentially be misinterpreted as perimortem wounds—that is, trauma inflicted at or around the time of death.
Different taphonomic processes also leave distinct signatures, so the ability to differentiate postmortem changes from perimortem trauma is critical. For example, tooth marks on bone from animal scavenging should not be misinterpreted as perimortem trauma. Taphonomic studies require close examination of the condition of the remains and any alterations caused by the environment. Humans are also considered taphonomic agents, as a perpetrator may be involved in transporting or altering (for example, mutilating or dismembering) remains after death.
Human remains are subject to numerous variables as they decompose; as a result, human taphonomy requires input from several different scientific fields, including anthropology, pathology, entomology, botany, soil science, and, in some cases, marine biology.
Stages of Decomposition
When human remains are discovered, one of the first questions asked is, How long has the victim been dead? Decomposition typically occurs in the following predictable sequence of stages: the fresh stage, the bloat stage, the active decay stage, the advanced decay stage, and the dry or skeletal stage. The rate of decay, however, is influenced by a number of factors in the immediate environment, such as temperature, humidity, moisture, availability of insects and animal scavengers, and soil conditions. Bodies that are found indoors or that are buried decompose at slower rates than remains that are deposited on the surface of the ground. In the case of a recent death, medicolegal investigators examine the body for early signs of decomposition.
Changes during the fresh stage of decomposition generally occur within the first few days postmortem. Immediately after death, the body cools until it reaches ambient temperature, a process known as algor mortis. Pooling of blood into the capillaries of the skin, or livor mortis, follows and is fixed by approximately twelve hours after death. Rigor mortis, the hardening of the muscles, begins about two hours after death but may last for up to twenty-four hours.
The bloat stage is marked by the buildup of gases within the body, which causes the abdomen to be distended. The skin also becomes discolored and marbled in appearance. This process may last for several days up to a month after death. Carrion-feeding insects such as blowflies and flesh flies also typically arrive at a corpse within minutes after death. The maggots from these flies use the body as a food source for several weeks to months.
During the active decay stage, maggots, beetles, and other insects reduce the mass of the corpse, and the chest cavity begins to collapse. In the advanced decay stage, remains are nearly skeletonized owing to insect and animal scavenger activity. Finally, in the dry or skeletal decay stage, the skeletonized remains are devoid of soft tissue and odor. Postmortem changes are somewhat predictable within a given region; however, the rate of decomposition is highly variable from region to region.
Taphonomic Studies
Although some taphonomic studies occur within laboratory settings, most research is conducted outdoors with the remains of nonhuman animals, such as pigs. In some locations, however, donated human cadavers are used to study decomposition rates; the Anthropological Research Facility at the University of Tennessee, Knoxville, popularly known as the Body Farm, is perhaps the most widely known example of this kind of research center.
With the establishment of increasing numbers of outdoor taphonomic research facilities in different locations, scientists have been able to gain reliable data on variations in decay rates. These studies, which contribute to an in-depth understanding of the process of human decomposition, provide law-enforcement investigators with information they need to make more accurate estimates of time since death.
Bibliography
Blau, S. "Anthropology: Taphonomy in the Forensic Context." Reference Module in Social Sciences, 2024, www.sciencedirect.com/topics/social-sciences/taphonomy. Accessed 19 Aug. 2024.
Galloway, Alison, et al. “Decay Rates of Human Remains in an Arid Environment: Retrospective Study of Decay Rates in the Southwestern United States.” Journal of Forensic Sciences 34 (May, 1989): 607–16.
Haglund, William D., and Marcella H. Sorg, eds. Advances in Forensic Taphonomy: Method, Theory, and Archaeological Perspectives. Boca Raton, Fla.: CRC Press, 2002.
Haglund, William D., et al., eds. Forensic Taphonomy: The Postmortem Fate of Human Remains, CRC Press, 2017.
Komar, Debra A. “Decay Rates in a Cold Climate Region: A Review of Cases Involving Advanced Decomposition from the Medical Examiner’s Office in Edmonton, Alberta.” Journal of Forensic Sciences 43 (January, 1998): 57–61.
Lyman, R. Lee. Vertebrate Taphonomy. New York: Cambridge University Press, 1994.