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.
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 , 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.