Taphonomy

Taphonomy, from the Greek, taphos, meaning tomb or grave, and nomy, meaning classification, is a field of paleontology, paleo-anthropology, and bioarcheology that studies human and animal remains in relation to the post-mortem (after death) transformations that occur in burial sites. In a broader sense, taphonomy is the study of the processes that leads to fossilization, as well as the stages of transformation of remains through the action of environmental factors. The knowledge gathered by this field is important to forensic science as a tool for the analysis of human remains at old crime scenes, mass graves, and mass disaster areas.

Osteology (or the study of bones), geochemistry, and entomology (the study of insects) are important aspects of taphonomy, as skeletons and skeletal fragments may yield information on the living conditions, availability of food, presence of infections, wear and tear of specific joints due to repetitive effort, size of muscles, and post-mortem events. Therefore, a scenario of living organism versus environmental characteristics may be inferred from such analysis as well as which forces and agents have acted over the remains after death. When the organism dies and is buried or covered by sedimentary layers of soil, such as clay, sand, volcanic ash, or ice, the taphonomic process of post-mortem transformations begins, which can lead to different types of mummification, decomposition , or skeletonization. If the conditions are right, skeletal fossilization will eventually occur. Bones can also be modified by animal scavenging, or be carried by rivers and scattered on riverbanks far from the original site of death before fossilization occurs.

Taphonomy studies three different stages of post-mortem transformation: necrology, biostratinomy, and diagenesis. Necrology refers to the factors present around the time of death or directly associated with the cause of death . Necrologic studies could include examination of bones or bodies for skull fractures, marks of fangs or claws in bones, signs of malnutrition, abscesses, infections, lesions by blunt instruments, bullets, or incineration, among other clues to the cause and events surrounding death. Biostratinomy identifies the changes that occurred after death such as decomposition and changes due to environmental forces acting in burial sites (tombs, graveyards, mass graves), or in places where remains were left or found, such as river or lake bottoms, sedimentary soils , or woods. Several events from this stage may leave their marks on the remains, such as animal scavenging, enzymatic and bacterial activity, insect activity, and transportation by water or landslides. Eventually, some bone fragments or entire skeletons may be buried under conditions that favor diagenesis, the process of lithification (compaction) of the sediments that envelop the remains, ultimately resulting in fossilized bones. Fossilization may occur in terrestrial (earth) and maritime (water) environments, and give clues to researchers about the environmental, geological, topographical, and climatic changes that occurred on Earth throughout the process of fossilization. The study of submarine layers of fossilized marine animals and crustaceans, for instance, allows the description of radical climate changes that occurred in different geological eras.

Forensic taphonomy focuses on the perimortem (at the time of death) and intermediate postmortem (days to weeks after death) biological and biochemical transformations in order to determine the cause of death, estimate the approximate time of death, and to identify humans remains including the sex, age, race, and, whenever possible, the individual's identity. The understanding of how different environments interfere with the biological and biochemical changes in human remains, affecting the process of decomposition, is crucial for the forensic interpretation of mass graves, mass disasters, war crimes, and cold cases of murder .

see also Animal evidence; Anthropology; Body Farm; Death, cause of; Decomposition; Entomology; Exhumation; Geology; Medical examiner; Mummies; Osteology and skeletal radiology; Pathology; Skeletal analysis; War forensics.

Taphonomy

Taphonomy is the study of how dead organisms are preserved in the fossil record. The term is derived from the Greek words taphos, which means grave, and nomos, which means law. Russian scientist and science fiction writer Ivan Antonovich Efremov (1907–72) is often credited with first using the word and concept of taphonomy in 1940 within the established field of paleontology. The field further developed during the late twentieth century when scientists applied patterns seen within taphonomy to such fields as behavioral paleobiology, biostratigraphy, and paleoceanography. More detailed scientific analysis of taphonomic data was then possible for scientists.

Taphonomists, those who work in the field of taphonomy, seek to understand how an organism died and what happened to its body before and during burial. Such scientists also try to determine what factors may have contributed to unequal representation of certain groups in the fossil record due to differences in their rates of preservation.

One of the challenges that taphonomists often face is the interpretation of fossilized broken bones. The scientists must determine if the damage occurred while the animal was alive, after it died, or even after the bone was buried. If the bone broke while the animal was alive, there may be new growth showing that the injury was healing. Bones broken after the animal died will not show any signs of healing. It is sometimes difficult to determine whether the damage occurred before burial, perhaps by gnawing or trampling, or afterward.

The study of preservation processes is central to taphonomy. There is much to be learned from the nature of a fossil’s preservation, but if a fossil is not well preserved, then there will be little evidence to study.

Rapid burial is crucial to good preservation for several reasons. For example, buried remains are much less likely to be disturbed by scavengers or swept away by rivers or other rapidly flowing bodies of liquid. Scavengers pull skeletons apart, scatter bones, and eat some parts preferentially to others. Rivers transport animal and plant remains far from the site of death. Indeed, most organisms are not buried where they die, but are first shuffled around either in part or in whole. This movement may be small, as in the sinking of a fish to the bottom of a lake, or extensive, as when an animal’s body floats hundreds of miles in ocean currents. A second reason is that burial, especially in fine-grained muds, may slow down bacterial decay so tissues are better preserved.

Of the organisms that eventually become fossilized, few are preserved intact. This is due to differences in the ability of various parts to resist decay. For instance, teeth and bones are very hard, and fossilized specimens are relatively common. However, it is quite a find to recover a fossilized heart or other soft part. Since soft parts nearly always decay, even if deeply buried, their pattern can only be preserved if minerals such as carbonate, pyrite, or phosphate replace the soft tissues. Such tissues will not decay if the organism happens to be buried in a sterile environment, such as amber or a peat bog.

The hard parts of an organism are held together by soft parts. When the soft parts decay, the organism’s anatomy often becomes jumbled and scattered. This condition may make it difficult to determine what type of organism a part came from, and sometimes different parts of the same organism are accidentally classified as different species. A case in point is Anomalocaris canadensis. Until intact specimens of this prehistoric animal were found, the body was thought to be a sea cucumber, the mouth a jellyfish, and the feeding appendages of shrimp like creatures. By helping to solve puzzles like this, taphonomists increase scientific understanding of the fossil record.

See also Fossil and fossilization.

Taphonomy

Taphonomy is the study of how organisms are preserved in the fossil record (the term is derived from the Greek word taphos, which means grave). Taphonomists seek to understand how an organism died and what happened to its body before and during burial. They also try to determine what factors may have contributed to unequal representation of certain groups in the fossil record due to differences in their rates of preservation.

One of the challenges taphonomists are often presented with is the interpretation of fossilized broken bones. The scientists must determine if the damage occurred while the animal was alive, after it died, or even after the bone was buried. If the bone broke while the animal was alive, there may be new growth showing that the injury was healing. Bones broken after the animal died will not show any signs of healing. Unfortunately, it is sometimes difficult to determine whether the damage occurred before burial, perhaps by gnawing or trampling, or afterwards.

The study of preservation processes is central to taphonomy. There is much to be learned from the nature of a fossil's preservation, but if a fossil is not well preserved, then there will be little evidence to study.

Rapid burial is crucial to good preservation. One reason is that buried remains are much less likely to be disturbed by scavengers or swept away by rivers . Scavengers pull skeletons apart, scatter bones, and eat some parts preferentially to others. Rivers transport animal and plant remains far from the site of death. Indeed, most organisms are not buried where they die, but are first shuffled around either in part or in whole. This movement may be small, as in the sinking of a fish to the bottom of a lake , or extensive, as when an animal's body floats hundreds of miles in ocean currents . A second reason is that burial, especially in fine-grained muds, may slow down bacterial decay so tissues are better preserved.

Of the organisms that eventually become fossilized, few are preserved intact. This is due to differences in the ability of various parts to resist decay. On the one hand, teeth and bones are very hard, and fossilized specimens are relatively common. On the other, it is quite a find indeed to recover a fossilized heart or other soft part. Since soft parts nearly always decay, even if deeply buried, their pattern can only be preserved if minerals such as carbonate, pyrite, or phosphate replace the soft tissues. Such tissues will not decay if the organism happens to be buried in a sterile environment such as amber or a peat bog.

The hard parts of an organism are held together by soft parts, and when these decay, the organism's anatomy often becomes jumbled and scattered. This may make it difficult to determine what type of organism a part came from, and sometimes different parts of the same organism are accidentally classified as different species . A case in point is Anomalocaris canadensis. Until intact specimens of this prehistoric animal were found, the body was thought to be a sea cucumber, the mouth a jellyfish , and the feeding appendages shrimp-like creatures. By helping to solve puzzles like this, taphonomists increase our understanding of the fossil record.

See also Fossil and fossilization.

taphonomy The study of the biological, chemical, and physical processes that change organisms after death, leading ultimately to their preservation as fossils in rock. The initial phase in this process is removal or decay of the organism's soft parts by scavengers or microbes. Thereafter the remaining hard parts, such as bones and shells, may undergo disarticulation and fragmentation, and are often moved from the site of death, for example by water currents or the wind. Exposure to such movements causes abrasion against other solid particles, and consequent erosion of sharp edges. Burial underneath sediment is common, resulting in flattening or collapse of shell or skeletal cavities, depending on their mechanical strength. The chemical components of the remains may also change; for example, the calcium carbonate of a shell may be converted from aragonite to calcite. Also, concretions of carbonates often form with shell cavities, sometimes protecting them from collapse. The physical and chemical processes occurring after burial of an organism's remains are termed diagenesis. Knowledge of all these processes, which may take thousands or millions of years, enables a fuller and more accurate interpretation of fossil remains.

taphonomy The study of the transition of all or part of an organism and its traces from the biosphere into the lithosphere (i.e. fossilization). The term was coined by J. A. Efremov in 1940.