Bioarchaeology is the study of human skeletons in archaeological sites, which can answer many questions concerning human behavior and ways of life of groups that occupied a site. Bioarchaeologists have extensive training in forensics, osteology (study of bones), and archaeological field methods. They typically study bones, bone fragments, hair, and depressions left by bodies in places like Pompeii, where volcanic ash entombed residents.
Archaeologists’ methods for analyzing human skeletons are similar to methods used for animal remains. First, it is important to determine if bones recovered from a site are, in fact, human rather than some other kind of animal. Archaeologists can often determine that from the context of the artifacts, including other materials associated with the bones. It is also important to determine whether the bones are part of a complete skeleton and whether they are isolated or are part of a burial population—a group of human burials in a limited area and from a relatively small period of time.
Much can be determined from complete skeletons and from certain “diagnostic” bones. Biological sex, for example, can be determined relatively easily from a complete skeleton that still has soft tissue. If the remains are strictly skeletal, determining biological sex requires training in osteology. The bones most commonly used to identify biological sex are in the pelvis. Adult male pelvic bones tend to be markedly smaller than adult female pelvic bones because of changes that occur during pregnancy and childbirth. The pelvic bones of females can also be marked by parturition scars that develop as a result of childbirth. The skull is the second most reliable bone used to determine biological sex. Male skulls are typically larger than female skulls, and there are other features that vary consistently by sex, including the size of the chin and the degree of protrusion of the bone between the eyes, which is called the glabella.
Once biological sex has been determined, archaeologists consider the age of the individual at death. In general, it is difficult to determine exact ages, but archaeologists can assign age ranges to skeletons: fetal refers to before birth, infant to 0 to 3 years, child to 3 to 12 years, adolescent to 12 to 20 years, young adult to 20 to 35 years, middle adult to 35 to 50 years, and older adult to older than 50 years. However, ancient and poorly preserved bones often can be reliably identified only as infant, child, or adult, which can be quite frustrating!
Dental eruption and wear are other common methods used to determine age at death. Dental eruption is quite reliable when evaluating younger individuals and is most reliable for individuals who were younger than 15 when they died. The timing of eruption of permanent teeth and loss of deciduous (baby) teeth varies somewhat but is fairly predictable (most of the children in one of the author’s daughter’s first grade class are missing front teeth!). Dental eruption cannot be used for adult skeletons since no eruptions occur after the third molars (wisdom teeth) come through. Dental wear, on the other hand, is useful only when analyzing older individuals. When using dental wear to assess age, archaeologists must consider the person’s likely diet since some foods, such as acorn meal, are abrasive and wear the teeth down relatively quickly.
Archaeologists can also use long bones such as leg and arm bones to estimate the age of children and young adults. When you are born, you have 300 bones; in your late twenties, you have only 206 bones. Where do the missing bones go? Well, they don’t actually go anywhere; instead, some bones fuse with other bones to form a new, single bone. At birth, our long bones consist of three separate segments—the two ends of the bone (epiphysis) and the shaft (diaphysis). Their fusion is a gradual process, and the age at which it begins and ends for each kind of bone is predictable so the degree to which the bones are fused in a skeleton is a fairly reliable indicator of age. One of the last bones to fuse is the collarbone (clavicle), which is not completely fused until about age 26 (there is some variation). Is your clavicle fused?
Once the fundamental questions of biological sex and age of a skeleton have been answered, archaeologists can analyze the bones for information about the individuals’ overall health and how they lived and died. They estimate an individual’s stature (height) from bones from the trunk, arms, and legs; caries (cavities) and wear on the enamel of teeth reveal information about the individual’s diet.
Paleopathology is the study of ancient diseases, disorders, and traumas revealed by skeletons. Many diseases affect bones, including osteoarthritis, nutritional deficiencies, and tuberculosis, which invades the sternum and chest bones and can collapse and fuse portions of the vertebral column. Visible and/or microscopic lines on long bones, called Harris lines (dense areas), and on teeth, called enamel hypoplasia, are signs of stunted growth due to malnutrition and/or nutrient deficiencies experienced when the bones and teeth were forming. Both can be seen via X-rays and are permanent. The width between the lines indicates how long the nutritional stress or deficiency lasted.
In osteoarthritis, cartilage between bones breaks down, causing the bones to rub against each other and leaving behind signs of wear that can be seen in skeletal remains. It was already common in ancient times. Osteoarthritis is also a sign of repetitive and mechanical stress on joints. Therefore, where osteoarthritis occurs in a skeleton gives archaeologists information about the individual’s activities. Women, for example, tend to develop arthritis in their lower backs, which can be associated with carrying their children on their backs in cradleboards and other types of infant carriers as well as with carrying baskets and other containers when harvesting food and collecting water.
Multiple remains from a burial population allow archaeologists to infer paleodemographic information—the overall health, typical life expectancy, and common causes of death in a group of people. Mortality profiles describe these characteristics for males and females and by age categories.
In recent years, archaeologists have begun to reconstruct the appearance of ancient peoples from their remains. This is a highly specialized task performed by forensic artists who understand the human skeleton and the locations and depths of connective tissue and fatty deposits. The reconstructions are based on scientific data but are still artistic endeavors, and many human features (such as hair color, hair style, and eye color) cannot be determined from skeletal evidence. DNA analysis, however, is beginning to provide information on skin, hair, and eye color.