The human skeleton has been somewhat nebulously defined as ‘a man with his insides out and his outsides off’. It is probably the most durable reminder of man's mortal existence and has intrigued, challenged, and stimulated morbid, mystical, and scientific minds from at least biblical times and probably before. To appreciate the public interest in this subject, one need only observe the media frenzy that ensues when a human skeleton is discovered. Paradoxically, the level of media interest seems to be almost inversely proportional to the academic value of a find. Remains that date from fossil times can have a monumental influence on our understanding of the evolution of our species but often attract less attention than more recent remains, especially if there is some hint of criminal involvement. It is the inseparable and inextricable nature of the bond between the skeleton and death which ensures that human bones are often perceived in a supernatural light that passes beyond common sense. Hopefully any sane anatomist will tell you that the bones in the dissecting room never rattle ominously and any sober gravedigger will assure you that they do not rise from their coffins and dance around the tombstones at midnight.
There are essentially five basic functions attributed to the skeleton. Each is arguably as important as the other, but given the evolutionary evidence for bone development, the primary function is probably to provide a stable framework that gives support and structure to the soft tissues. Various clinical conditions such as osteomalacia, osteoporosis, and osteogenesis imperfecta bear witness to the inadequacies of poorly formed bone in fulfilling the role of support to the human body. The skeleton also plays a protective role and this is most clearly seen in the region of the skull, which not only forms a box around the delicate tissues of the brain, but also serves to protect the special senses of sight, smell, and hearing. It is said that the thorax protects the heart and lungs, but this theory has little merit when one considers that equally delicate structures in the abdomen are not guarded in this way. It is more likely that the bones of the thorax are involved in the third function of the skeleton, which is to provide a rigid framework for the attachment of muscles and, in the case of the thorax, thereby facilitate breathing. For efficient movement to occur, each muscle must originate on the surface of one bone, pass across a joint and insert onto the surface of another bone. In this way one can accurately predict the movement produced by the contraction of each individual muscle or muscle group. The fourth function of the skeleton is to house sites of haemopoetic (blood-making) activity within the red marrow that occupies the cancellous spaces of many bones. In bone marrow transplantation, the blood-forming cells are aspirated from sites rich in red marrow, such as the iliac blade of the pelvic bone and the sternum. The final function of the skeleton is to provide a reservoir of minerals (calcium, phosphates, potassium, and many other trace elements), which the body can call upon to replenish depleted levels.
There is a myth that bone is an inactive, dry, and dusty material. This is reflected in the origin of the term ‘skeleton’, which is derived from the Greek word skeletos meaning ‘dried up’. However quite the opposite is true in life, as bone is unquestionably a dynamic tissue that will bleed if it is cut, hurt if it is damaged, and mend itself if it is broken. Furthermore, it will be resorbed if it is not needed and conversely will develop where it is required.
The adult human skeleton. From Luther Holden (1882) Human Osteology: a description of the bones. J. T. A. Churchill, London
The official statement, although a virtually meaningless concept, concludes that there are 206 individual bones in the adult skeleton. However, when one considers that over forty inconstant accessory bones have been described in the foot alone, it is clear that, whilst of some value in a trivia quiz, the statement is essentially meaningless. Bones are classified according to either their location within the body or their shape. The latter should be avoided where possible, as the wide variety of bone shapes almost seems to defy useful classification. Whilst the skeleton is bilaterally symmetrical, those structures that lie on the midline do not have a corresponding partner and therefore form the axis, and hence the ‘axial’ skeleton (see Figure). This comprises the skull, the vertebral column (24 presacral, cervical, thoracic, and lumbar vertebrae; the sacrum; and the coccyx), and the sternum. The limbs and their attachments to the axial skeleton (girdles) belong to the ‘appendicular’ skeleton and are all paired. The pectoral girdle (scapula and clavicle) attaches the upper limb to the axial skeleton whilst the pelvic girdle (innominate bone) attaches the lower limb to the axial elements. In addition, the rib cage attaches the sternum in front to the vertebral column behind.
Each bone displays an intimate correlation between form and function. This relationship is fundamentally governed by a variety of factors including genetics, mechanics, and metabolism. It is clear however that the human skeleton is unlike that of any other animal and this uniqueness is exploited in the science of osteology, where recognition of ‘human’ plays a vital role. The human skeleton is different for many reasons, including the fact that we are the only habitual biped with upper limbs that are solely dedicated to manipulation and not involved in locomotion. Relatively speaking, we also have the largest brain and give birth to babies with relatively large heads. All of these factors, plus many others, lead to levels of specialization in our skeleton that allow anthropologists (both archaeological and forensic) to persuade our bones to give up many secrets regarding our identity and way of life. One of the first steps in the analysis of human skeletal remains is to establish whether or not they are human, since a murder investigation initiated on the misidentification of some sheep bones is unlikely to be successful. The second question is often an attempt to establish how long the person has been deceased. If more than 70 years have elapsed since death then the remains are classified as archaeological, but if they are more recent then it is a forensic problem. Biological identity is one of the first things to be established and this includes sex, age at death, stature, and race. Beyond that, information regarding individual identity may be established through recognition of personal idiosyncrasies (previous fractures, dental treatment, previous diseases, congenital anomalies, etc.), all of which might lead to a positive identification of the deceased in a forensic situation. Given an intact skeleton, sex can be determined with up to 95% accuracy, and whilst this is relies heavily on differences in the pelvis, every bone displays some degree of sexual dimorphism. The determination of age at death is accurate if the individual was younger than 25 years of age but becomes more difficult with advancing age as there are degenerative changes which occur at different rates in different individuals. Stature is relatively easy to determine as it involves measuring the lengths of the limb bones and inserting the values into previously computed regression equations. The ethnic affinity of skeletal remains is very difficult to assess and normally requires the skull to be intact and to show characteristic racial traits. In cases of trauma-related deaths, evidence of the cause of death may remain on the skeleton, such as bullet entry and exit wounds, fractures caused by implements such as hammers or crow bars and also, in cases of stabbing, blades may penetrate and leave marks on the underlying bone. It is probably true that the most important evidence left behind at the scene of a homicide is the body, and this holds true even if it is not discovered for a very long time and only the skeleton remains.
— Sue M. Black
Bibliography
- Brothwell, D. R. (1981). Digging up bones. The excavation, treatment and study of human skeletal remains. Oxford University Press, Oxford.
- Reichs, K. J. (1998). Forensic osteology: advances in the identification of human remains, (
2nd edn ). CC Thomas, Illinois
See also anthropology; bone; joints; pelvis; skull.
