The majority of the skeletal analysis process revolves around the identity of the deceased individual. However, there is one last, very important question bioarchaeologists and forensic anthropologists should ask: What happened to the remains after death? Generally speaking, processes that alter the bone after death are referred to as taphonomic changes.
The term taphonomy was originally used to refer to the processes through which organic remains mineralize, also known as fossilization. Within the context of biological anthropology, the term taphonomy is better defined as the study of what happens to human remains after death. Initial factors affecting a body after death include processes such as decomposition and scavenging by animals. However, taphonomic processes encompass much more than the initial period after death. For example, plant root growth can leach minerals from bone, leaving a distinctive mark. Sunlight can bleach human remains, leaving exposed areas whiter than those which remained buried. Water can wear the surface of the bone until it becomes smooth.
Some taphonomic processes can help a forensic anthropologist estimate the relative amount of time human remains have been exposed to the elements. For example, root growth through a bone would certainly indicate a body was buried for more than a few days. Forensic anthropologists must be very careful when attempting to estimate time since death based on taphonomic processes as environmental conditions can greatly influence the rate at which taphonomic processes progress. For example, in cold environments, tissue may decay slower than in warm, moist environments.
The study of the decomposition and placement of an individual’s body in the grave can also help bioarchaeologists understand more about how the body was placed and treated, and if there were any rituals that took place during the burial. For example, ochre, a mineral used as a pigment in paintings and dyes throughout human history, can stain bone and be an indication of ceremonial practice related to burial. Likewise, corrosion of different kinds of metals placed as grave goods or used as material in coffins can stain bone. For example, in a sample of medieval and post-medieval Spanish and Basque skeletons from the Cathedral of Santa Maria, Kimberly Hopkinson and colleagues (2008) noted a bright green to turquoise staining in some of the skeletons’ teeth. The researchers believe that the staining was due to an ancient Greek practice of placing a coin in the mouth of the deceased to serve as the payment for the ferryman of Hades, Charon, who transported the deceased across the river that divided the world of the living from that of the dead. Hopkinson and colleagues determined that as the copper component of the bronze coins reacted with acid, it stained the teeth and surrounding bone, leaving evidence of the ancient Greek burial practice.
Both bioarchaeologists and forensic anthropologists must contend with taphonomic processes that affect the preservation of bones. For example, high acidity in the soil can break down human bone to the point of crumbling. In addition, when noting trauma, they must be very careful not to confuse postmortem (after death) bone damage with trauma.
A short description and photographic examples of several different types of taphonomic processes are shown below.
Figure \(\PageIndex{1}\): Rodent gnawing.
Rodent gnawing: When rodents, such as rats and mice, chew on bone, they leave sets of parallel grooves. The shallow grooves are etched by the rodent’s incisors (Figure 15.26).
Figure \(\PageIndex{2}\): Carnivore damage.
Carnivore damage: Like rodents, carnivores leave destructive dental marks on bone. Tooth marks may be visible be in form of pit marks or punctures from the canines, as well as extensive gnawing or chewing of the ends of the bones to retrieve marrow (Figure 15.27).
Figure \(\PageIndex{3}\): Burned bone.
Burned bone: Fire causes observable damage to bone. Temperature and the amount of time bone is heated affect the appearance of the bone. Very high temperatures can crack bone and result in white coloration. Color gradients are visible in between high and lower temperatures, with lower temperatures resulting in black coloration from charring. Cracking can also reveal information about the directionality of the burn (Figure 15.28).
Figure \(\PageIndex{4}\): Root etching.
Root etching: Plants can alter bone. Specifically, plant roots can etch the outer surface of the bone, leaving grooves where the roots attached as they leached nutrients. During this process, the plant’s roots secrete acid that breaks down the surface of the bone (Figure 15.29).
Figure \(\PageIndex{5}\): Weathering.
Weathering: Many different environmental conditions affect bone. River transport can smooth the surface of the bone due to water abrasion. Sunlight can bleach the exposed surface of bone. Dry and wet environments or the mixture of both types of environments can cause cracking and exfoliation of the surface. Burial in different types of soil can cause discoloration, and exposure can cause degreasing (Figure 15.30).
Figure \(\PageIndex{6}\): Cut marks.
Cut marks: Humans also alter bone by cutting, scraping, or sawing it directly or in the process of removing tissue. The groove pattern—that is, the depth and width of the cuts—can help identify the tool used in the cutting process (Figure 15.31).
Figure \(\PageIndex{1}\): Rodent gnawing.
Figure \(\PageIndex{2}\): Carnivore damage.
Figure \(\PageIndex{3}\): Burned bone.
Figure \(\PageIndex{5}\): Weathering.
Figure \(\PageIndex{6}\): Cut marks.