Paleopathology
Paleopathology, also spelled palaeopathology, is the study of ancient diseases and injuries in organisms through the examination of fossils, mummified tissue, skeletal remains, and analysis of coprolites. Specific sources in the study of ancient human diseases may include early documents, illustrations from early books, painting and sculpture from the past. All these objects provide information on the evolution of diseases as well as how past civilizations treated conditions. Studies have historically focused on humans, although there is no evidence that humans are more prone to pathologies than any other animal.
The word paleopathology is derived from the Ancient Greek roots of palaios meaning "old", pathos meaning "experience" or "suffering", and -logia, "study".
Paleopathology is an interdisciplinary science, meaning it involves knowledge from many sectors including "clinical pathology, human osteology, epidemiology, social anthropology, and archaeology". It is unlikely that one person can be fluent in all necessary sciences. Therefore, those trained in each are important and make up a collective study. Training in anthropology and archaeology is arguably most important, because the analysis of human remains and ancient artifacts are paramount to the discovery of early disease.
History
Historical evidence shows that deviations from good health have long been an interest to humans. Although the content that makes up this study can be traced through ancient texts, the term "paleopathology" did not have much traction until the 20th century. This time period saw an increase in case studies and "published reports on ancient diseases". Ancient texts that are thousands of years old record instances of diseases such as leprosy.From the Renaissance to the mid-nineteenth century, there was increasing reference to ancient disease, initially within prehistoric animals although later the importance of studying the antiquity of human disease began to be emphasized. Some historians and anthropologists theorize that "Johann Friederich Esper, a German naturalist...heralds the birth of paleopathology." Although it wasn't until between the mid nineteenth century and World War I that the field of human paleopathology is generally considered to have come about. During this period, a number of pioneering physicians and anthropologists, such as Marc Armand Ruffer, G. Elliot Smith, Frederic Wood Jones, Douglas E. Derry, and Samuel George Shattock, clarified the medical nature of ancient skeletal pathologies. This work was consolidated between the world wars with methods such as radiology, histology and serology being applied more frequently, improving diagnosis and accuracy with the introduction of statistical analysis. It was at this point that paleopathology can truly be considered to have become a scientific discipline. Today, the use of biomedical technology like DNA and isotopic analysis are major developments for pathological knowledge.
After World War II paleopathology began to be viewed in a different way: as an important tool for the understanding of past populations, and it was at this stage that the discipline began to be related to epidemiology and demography.
New techniques in molecular biology also began to add new information to what was already known about ancient disease, as it became possible to retrieve DNA from samples that were centuries or millennia old.
Methods and techniques
To analyze human remains of the past, different techniques are used depending on the type of remains that are found. For example, "the approach to palaeopathological samples depends on the nature of the sample itself, its size, the degree of preservation and, very importantly, the manipulation allowed." Much research done by archaeologists and paleopathologists is on bones. The basic nature of bones allows them to not degrade over time like other human remains would, making osteopathology important in studying ancient disease. Human osteopathology is classified into several general groups:Whilst traumatic injuries such as broken and malformed bones can be easy to spot, evidence of other conditions, for example infectious diseases such as tuberculosis and syphilis, can also be found in bones. Arthropathies, that is joint diseases such as osteoarthritis and gout, are also not uncommon.
The first exhaustive reference of human paleopathology evidence in skeletal tissue was published in 1976 by Ortner & Putschar. In identifying pathologies, physical anthropologists rely heavily on good archaeological documentation regarding location, age of site and other environmental factors. These provide the foundation on which further analysis is built and are required for accurate populations studies. From there, the paleopathology researcher determines a number of key biological indicators on the specimen including age and sex. These provide a foundation for further analysis of bone material and evaluation of lesions or other anomalies identified.
Archaeologists increasingly use paleopathology as an important main tool for understanding the lives of ancient peoples. For example, cranial deformation is evident in the skulls of the Maya, where a straight line between nose and forehead may have been preferred over an angle or slope. There is also evidence for trepanation, or drilling holes in the cranium, either singly or several times in a single individual. Partially or completely healed trepanations indicate that this procedure was often survived. The 10,000 year-old human remains discovered at the site of Nataruk in Turkana, Kenya, reportedly show extreme traumatic lesions to the head, neck, ribs, knees and hands, including embedded stone projectiles, and they may represent the earliest evidence of inter-group conflict between hunter-gatherers in the past.
Trauma analysis in paleopathology
Few diseases leave evidence on skeletal remains, however, osteological analysis of remains has the benefit of being able to describe and diagnose skeletal remains without the presence of soft tissue. Paleopathologies are divided into seven suggested categories for analysis:- Anomalies
- Trauma repair
- Inflammatory/Immune
- Circulatory
- Metabolic
- Neuromechanical
- Cancers
Skeletal trauma
- Partial or complete break
- Abnormal displacement or dislocation
- Disruption of blood supply
- Artificially induced abnormal shape or contouring
Fractures are the result of enough force being applied to bone to mechanically alter it. Tension, compression, torsion, and bending or shearing each leave its own characteristics on skeletal remains. The type, severity, number, timing and location of fractures are important for delineating between accidental and violent trauma and the data recovered from analysis reveal the meaning of that violence. Fractures present substantial problems for the skeletal areas located around the point of initial trauma and may leave accompanying secondary pathological evidence due to tissue death, deformity, and arthritis.
Types of trauma encountered during analysis might include blunt force trauma, sharp force trauma, projectile, heat, and chemical. Evidence of trauma in skeletal remains can vary depending on the type of bone affected; for example, blunt force trauma from a club will present differently than sharp force trauma inflicted by a sword.
During analysis, evidence of antemortem healing of a fracture allows it to be compared with both perimortem and postmortem trauma. Antemortem healing will present as a callus at the location of the fracture. As White notes, “The rate of fracture repair depends on alignment, amount of movement at the site of fracture and the health, age, diet, and blood supply of the individual.”
Violence
Differentiating skeletal trauma as the result of violence compared to that caused by accidental or other causes is achieved by integrating the skeletal analysis of mechanical injury to bone with the sociocultural context. Intertwining the biological analysis with the sociocultural factors presented by not just the individual but also the larger group context has allowed bioarchaeology to identify numerous types of violence including, as The Routledge Handbook of Paleopathology notes,“warfare, ritualized combat, hand to hand fighting, raids and ransacking, massacres, torture, executions, witchcraft, captive taking, slavery, anthropophagy, intimate partner and child abuse, scalping and human sacrifice." Without this synthesis of the biological analysis and social theory, Klaus notes that trauma studies are reduced to “simply descriptions of trauma found on bone.”Archaeological infectious diseases
Several diseases are present in the archaeological record. Through archaeological evaluation these diseases can be identified and sometimes can explain the cause of death for certain individuals. Aside from looking at sex, age, etc. of a skeleton, a paleopathologist may analyze the condition of the bones to determine what sort of diseases the individual may have had. The goal of a forensic anthropologist looking at the paleopathology of certain diseases is to determine if the disease they are researching are still present over time, with the occurrence of certain events, or if this disease still exists today and why this disease may not exist today. Diseases identifiable from changes in bone include:Apart from bones, molecular biology has also been used as a tool of paleopathology over the last few decades, as DNA can be recovered from human remains that are hundreds of years old. Since techniques such as PCR are highly sensitive to contamination, meticulous laboratory set-ups and protocols such as "suicide" PCR are necessary to ensure that false positive results from other materials in the laboratory do not occur.
For example, the long-held assumption that bubonic plague was the cause of the Justinian plague and the Black Death has been strongly supported by finding Yersinia pestis DNA in mass graves, whereas another proposed cause, anthrax, was not found.