Forensic anthropology is the application of the anatomical science of anthropology and its various subfields, including forensic archaeology and forensic taphonomy, in a legal setting. A forensic anthropologist can assist in the identification of deceased individuals whose remains are decomposed, burned, mutilated or otherwise unrecognizable, as might happen in a plane crash. Forensic anthropologists are also instrumental to the investigation and documentation of genocide and mass graves. Along with forensic pathologists, forensic dentists, and homicide investigators, forensic anthropologists commonly testify in court as expert witnesses. Using physical markers present on a skeleton, a forensic anthropologist can potentially determine a victim's age, sex, stature, and ancestry. In addition to identifying physical characteristics of the individual, forensic anthropologists can use skeletal abnormalities to potentially determine cause of death, past trauma such as broken bones or medical procedures, as well as diseases such as bone cancer. The methods used to identify a person from a skeleton relies on the past contributions of various anthropologists and the study of human skeletal differences. Through the collection of thousands of specimens and the analysis of differences within a population, estimations can be made based on physical characteristics. Through these, a set of remains can potentially be identified. The field of forensic anthropology grew during the twentieth century into a fully recognized forensic specialty involving trained anthropologists as well as numerous research institutions gathering data on decomposition and the effects it can have on the skeleton. Today, forensic anthropology is a well established discipline within the forensic field. Anthropologists are called upon to investigate remains and to help identify individuals from bones when other physical characteristics which could be used to identify a body no longer exist. Forensic anthropologists work in conjunction with forensic pathologists to identify remains based on their skeletal characteristics. If the victim is not found for a lengthy period of time or has been eaten by scavengers, flesh markers used for identification would be destroyed, making normal identification difficult if not impossible. Forensic anthropologists can provide physical characteristics of the person to input into missing person databases such as that of the National Crime Information Center in the US or INTERPOL's yellow notice database. In addition to these duties, forensic anthropologists often assist in the investigation of war crimes and mass fatality investigations. Anthropologists have been tasked with helping to identify victims of the 9/11 terrorist attacks as well as plane crashes such as the Arrow Air Flight 1285 disaster and the USAir Flight 427 disaster where the flesh had been vaporized or so badly mangled that normal identification was impossible. Anthropologists have also helped identify victims of genocide in countries around the world, often long after the actual event. War crimes anthropologists have helped investigate include the Rwandan Genocide and the Srebrenica Genocide. Organizations such as the Forensic Anthropology Society of Europe, the British Association for Forensic Anthropology, and the American Society of Forensic Anthropologists continue to provide guidelines for the improvement of forensic anthropology and the development of standards within the discipline. The use of anthropology in the forensic investigation of remains grew out of the recognition of anthropology as a distinct scientific discipline and the growth of physical anthropology. The field of anthropology began in the United States and struggled to obtain recognition as a legitimate science during the early years of the twentieth century. Earnest Hooton pioneered the field of physical anthropology and became the first physical anthropologist to hold a full-time teaching position in the United States. He was an organizing committee member of the American Association of Physical Anthropologists along with its founder Aleš Hrdlička. Hooton's students created some of the first doctoral programs in physical anthropology during the early 20th century. In addition to physical anthropology, Hooton was a proponent of criminal anthropology. Now considered a pseudoscience, criminal anthropologists believed that phrenology and physiognomy could link a person's behavior to specific physical characteristics. The use of criminal anthropology to try to explain certain criminal behaviors arose out of the eugenics movement, popular at the time. It is because of these ideas that skeletal differences were measured in earnest eventually leading to the development of anthropometry and the Bertillon method of skeletal measurement by Alphonse Bertillon. The study of this information helped shape anthropologists' understanding of the human skeleton and the multiple skeletal differences that can occur. Another prominent early anthropologist, Thomas Wingate Todd, was primarily responsible for the creation of the first large collection of human skeletons in 1912. In total, Todd acquired 3,300 human skulls and skeletons, 600 anthropoid skulls and skeletons, and 3,000 mammalian skulls and skeletons. Todd's contributions to the field of anthropology remain in use in the modern era and include various studies regarding suture closures on the skull and timing of teeth eruption in the mandible. Todd also developed age estimates based on physical characteristics of the pubic symphysis. Though the standards have been updated, these estimates are still used by forensic anthropologists to narrow down an age range of skeletonized remains. These early pioneers legitimized the field of anthropology, but it was not until the 1940s, with the help of Todd's student, Wilton M. Krogman, that forensic anthropology gained recognition as a legitimate subdiscipline. During the 1940s, Krogman was the first anthropologist to actively publicize anthropologists' potential forensic value, going as far as placing advertisements in the FBI Law Enforcement Bulletin informing agencies of the ability of anthropologists to assist in the identification of skeletal remains. This period saw the first official use of anthropologists by federal agencies including the FBI. During the 1950s, the U.S. Army Quartermaster Corps employed forensic anthropologists in the identification of war casualties during the Korean War. It was at this time that forensic anthropology officially began. The sudden influx of available skeletons for anthropologists to study, whose identities were eventually confirmed, allowed for the creation of more accurate formulas for the identification of sex, age, and stature based solely on skeletal characteristics. These formulas, developed in the 1940s and refined by war, are still in use by modern forensic anthropologists. The professionalization of the field began soon after, during the 1950s and 1960s. This move coincided with the replacement of coroners with medical examiners in many locations around the country. It was during this time that the field of forensic anthropology gained recognition as a separate field within the American Academy of Forensic Sciences and the first forensic anthropology research facility and body farm was opened by William M. Bass. Public attention and interest in forensic anthropology began to increase around this time as forensic anthropologists started working on more high-profile cases. One of the major cases of the era involved anthropologist Charles Merbs who helped identify the victims murdered by Ed Gein.