Paleopathology, also spelled palaeopathology, is the study of ancient diseases. Studying pathologies, these abnormalities in biologic individuals and systems, may be intrinsic to the system itself (examples: autoimmune disorders or traumatic arthritis) or caused by an extrinsic factor (examples: viruses or lead poisoning from pipes). Any living organism can have a pathology. Studies have historically focused on humans, but there is no evidence that humans are more prone to pathologies than any other animal.
Paleopathology is an interdisciplinary science. The majority of the work has historically been done by anthropologists studying diseases in ancient cultures. Medically trained professionals have also made substantial contributions, especially in modern comparative studies. Paleontologists have sporadically contributed to the field, focusing on non-avian dinosaurs and Cenozoic mammals.
History of paleopathology
Humans have always been interested in deviations from health. Ancient texts that are thousands of years old record instances of diseases such as leprosy. Historically, disease has often been correlated with morality, but this view has gradually given way to modern disease theory.
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. The true genesis of the field of human palaeopathology is generally considered to have occurred between the mid nineteenth century and World War I. 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 clarification included a review of human paleopathology published by H.U. Williams in 1929 and a book published by Pales in 1930 on paleopathology and comparative pathology. 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 palaeopathology can truly be considered to have become a scientific discipline.
After World War II palaeopathology 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 melinnia old. DNA older than
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, show extreme traumatic lesions to the head, neck, ribs, knees and hands, including embedded stone projectiles, and represent the earliest evidence of inter-group conflict between hunter-gatherers in the past.
Infectious diseases in the archaeological record
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 analyize the condition of the bones to determine what sort of diseases the individual may have. 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. Some disease that are found based on 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 
Some diseases are difficult to evaluate in the archaeology, however, tuberculosis can be found and dates as far back as the Neolithic period. Tuberculosis is presumed to have been transmitted from domesticated cattle to humans through ingestion of contaminated meats and the drinking of contaminated milk. It is also possible to contract tuberculosis through contact with infected persons. When an infected person coughs, they eject infected mucus from their body which can possibly infect those close by. There are several types of tuberculosis, the kind that affect cold-blooded animals, the kind that affects birds and the bovine type that causes disease in humans. Because bovine tuberculosis is often found in children, it may be that the disease is spread through the consumption of contaminated milk.
Tuberculosis manifests itself in the archaeological record through DNA extraction from the skeletal remains of people. Tuberculosis rarely manifests itself in the skeleton of individuals and when it does, it is usually only in advanced stages of the disease. The tuberculosis bacteria stays in the growth centers and spongy areas of the bone. This disease has a very long period of maturation, or the time it takes the disease to reach its full destructive potential. Because of the long period of development in the body, tuberculosis damages the body and then the body has time to repair itself. The evidence of the disease in bones can be seen in the destruction and healing of the bone structures especially in joints. Tuberculosis therefore appears in the archaeology record in the knee and hip joints and also the spine.
It was thought that there was no tuberculosis infection in North America before the arrival of Europeans but recent findings from the 80's and 90's have overturned that idea. Through extraction of DNA within the bone tuberculosis was not only found, but also dated to have been present in the Americas since 800 BC. Tuberculosis is a disease that thrives in dense populations. So the implications of finding tuberculosis in pre-Columbian society indicates that there was a large thriving community at the time. The earliest evidence of tuberculosis has been found in Italy dating to the 4th millennium BC. Evidence of tuberculosis has also been found in mummies from ancient Egypt dating to the same period. There is however, a lack of medical texts from ancient European and Mediterranean regions describing diseases that are identifiable as Tuberculosis but the bones show that there was a disease of this type.
Syphilis is a disease classified in a category of Treponemal disease. This group includes diseases like pinta, yaws, endemic syphilis and venereal syphilis. These diseases have symptoms that include inflammatory changes in tissues throughout the body. Initially the infected person may notice an area of inflammation at the site where the bacteria entered the body. Then the individual can expect more widespread soft tissue changes and lastly the diseases start to affect the bones. However, Only 10-20 percent of people infected with venereal syphilis show bone changes. Venereal syphilis has more severe symptoms than the other types of treponemal disease. Nervous system and circulatory disruption are unique to venereal syphilis and are not seen in yaws, endemic syphilis or pinta.
Bone changes can be seen in the archaeological record through lesions on the surface on the bone. In venereal syphilis the bone change is characterized by damage to the knees and joints. The damaged joints could be the source of infection or they could be damaged because of disruption in the nervous systems and ability to feel. In the beginning stages of the disease, the bone forms small lesions on the skull and tibiae. These lesions are caused mostly by inflammation of the marrow. In the final stages of the disease the bones start to be destroyed. Lesions that are formed tend to look similar to "worm holes" in the bone and are seen in the skull as well as large bones in the body. Most of the bone that is destroyed is due to secondary infections.
Syphilis has been seen in the Americas and Europe alike but there is debate as to what the origin of the disease is. Columbus and his sailors were said to have brought it to the Americas, however, Europeans blame Columbus for bringing the disease to Europe. There has not been any evidence of bone lesions associated with the disease that Columbus and the Europeans describe. The debate on the origins of venereal syphilis has been the subject of scientific discussions for hundreds of years and has recently been discussed and debated. At the first International Congress on the Evolution and Paleoepidemiology the subject was examined and debated by scholars from all over the world. There was no conclusive decision made as to the origin of venereal syphilis. There is however, more archaeological evidence for the disease in the Americas than there is for the disease in Europe at the time of Columbus's expeditions.
Many diseases are also closely linked to animal domestication, making paleopathology an economically important factor. Many animals that have been domesticated by humans have limited genetic variation compared to wild cousins, making them particularly susceptible to disease both today and in the past. Good examples of this limited genetic variation today include cattle ranches, beekeeping, horse racing, and dog breeding.
Archaeologists often study pathologies in the animals preserved in a human context. This could mean a burial ground or buried village where animals were cut up for food or perhaps animal bones were used for religious purposes. Baker and Brothwell’s seminal work  was published in 1980 and is still considered a classic text, being frequently referred to within the discipline. However, this position of importance has largely come about, not because of its comprehensive coverage, but because there has been no real alternative. Most palaeopathological literature is to be found in periodicals or compiled publications of conference papers. No synthesis of the research in the field as a whole has been attempted for the last twenty-five years.
Paleontologists have often studied paleopathologies in individual specimens, often with the intent of inferring behavior. For example, many Theropod dinosaur individuals show healed fractures and puncture wounds in their bones, suggesting aggressive and/or territorial behavior. Mosasaurs show evidence of getting a version of the decompression syndrome while diving. Ancient rhinos show evidence of osteopathologies related to their weight and possibly activity level or environment. The extinct mammal Spinolestes displays the earliest possible evidence of dermatophytosis. Recent interest has also been given to the absence of disease. Both naked mole-rats and elephants exhibit extremely low cancer rates today. Ancient DNA from the ancestors of these two lineages might help us understand how cancer resistance evolved.
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