Paleopathology and Paleomedicine
One of our most appealing and persistent myths is that of the Golden Age, a time before the discovery of good and evil, when death and dis- ease were unknown. But, scientiﬁc evidence—meager, fragmentary, and tantalizing though it often is—proves that disease is older than the human race and was not uncommon among other species. Indeed, stud- ies of ancient fossil remains, skeletons in museum collections, animals in zoos, and animals in the wild demonstrate that arthritis is widespread among a variety of medium and large-sized mammals, including aardvarks, anteaters, bears, and gazelles. Evidence of infection has been found in the bones of prehistoric animals, and in the soft tissues of mummies. Modern diagnostic imaging techniques have revealed evidence of tumors in fossilized remains. For example, researchers performing CT-scans of the brain case of a 72-million-year-old gorgo- saurus discovered a brain tumor that probably impaired its balance and mobility. Other abnormalities in the specimen suggested that it had suffered fractures of a thigh, lower leg, and shoulder.
Thus, understanding the pattern of disease and injury that afﬂicted our earliest ancestors requires the perspective of the paleopathologist. Sir Marc Armand Ruffer (1859–1917), one of the founders of paleopathol- ogy, deﬁned it as the science of the diseases that can be demonstrated in human and animal remains of ancient times. Paleopathology provides information about health, disease, death, environment, and culture in ancient populations.
In order to explore the problem of disease among the earliest humans, we will need to survey some aspects of human evolution, both biological and cultural. In Descent of Man and Selection in Relation to Sex (1871) Charles Darwin argued that human beings, like every other species, evolved from previous forms of life by means of natural se- lection. According to Darwin, all the available evidence indicated that
‘‘man is descended from a hairy, tailed, quadruped, probably arboreal
in its habits.’’ Despite the paucity of the evidence available to him, Darwin suggested that the ancient ancestor of modern human beings was related to that of the gorilla and the chimpanzee. Moreover, he predicted that the ﬁrst humans probably evolved in Africa. Evidence from the study of fossils, stratigraphy, and molecular biology suggests that the separation of the human line from that of the apes took place in Africa about ﬁve million to eight million years ago.
The fossilized remains of human ancestors provide valuable clues to
the past, but such fossils are very rare and usually incomplete. South African anatomist Raymond Dart made the ﬁrst substantive discovery of human ancestors in Africa in the 1920s when he identiﬁed the famous fossils known as Australopithecus africanus (South African Ape-man). The most exciting subsequent twentieth-century discoveries of ancient human ancestors are associated with the work of Louis and Mary Leakey and that of Donald Johanson. Working primarily at sites in Olduvai Gorge and Laetoli in Tanzania, Mary and Louis Leakey identiﬁed many hominid fossils, including Australopithecus boisei and Homo habilis. Johanson’s most important discovery was the unusually complete skeleton of a primitive australopithecine (Australopithecus afarensis), commonly referred to as Lucy. New hominid remains discovered at the beginning of the twenty-ﬁrst century stimulated further controversy about the earliest hominid ancestors, as well as those of the chimpanzee.
Paleoanthropology is a ﬁeld in which new discoveries inevitably
result in the re-examination of previous ﬁndings and great debates rage over the identiﬁcation and classiﬁcation of tiny bits of bones and teeth. Further discoveries will no doubt add new insights into the history of human evolution and create new disputes among paleoanthropologists. Scientists also acknowledge that pseudopaleopathologic conditions can lead to misunderstanding and misinterpretation because they closely resemble disease lesions, but are primarily the result of postmortem pro- cesses. For example, because the primary chemical salts in bones are quite soluble in water, soil conditions that are conducive to leaching out calcium can cause changes in bones like those associated with osteoporosis. Despite all the ambiguities associated with ancient remains, many traumatic events and diseases can be revealed by the methods of paleopathology.
Insights from many different disciplines, including archeology, his- torical geography, morphology, comparative anatomy, taxonomy, genet- ics, and molecular biology have enriched our understanding of human evolution. Changes in DNA, the archive of human genealogy, have been used to construct tentative family trees, lineages, and possible patterns of early migrations. Some genes may reveal critical distinctions between humans and other primates, such as the capacity for spoken language.
Anatomically modern humans ﬁrst emerged some 130,000 years
ago, but fully modern humans, capable of sophisticated activities, such as the production of complex tools, works of art, and long distance
trade, seem to appear in the archaeological record about 50,000 years ago. However, the relationship between modern humans and extinct hominid lines remains controversial.
The Paleolithic Era, or Old Stone Age, when the most important
steps in cultural evolution occurred, coincides with the geological epoch known as the Pleistocene or Great Ice Age, which ended about
10,000 years ago with the last retreat of the glaciers. Early humans were hunter-gatherers, that is, opportunistic omnivores who learned to make tools, build shelters, carry and share food, and create uniquely human social structures. Although Paleolithic technology is characterized by the manufacture of crude tools made of bone and chipped stones and the absence of pottery and metal objects, the people of this era produced the dramatic cave paintings at Lascaux, France, and Altamira, Spain. Presumably, they also produced useful inventions that were fully bio- degradable and, therefore, left no traces in the fossil record. Indeed, during the 1960s feminist scientists challenged prevailing assumptions about the importance of hunting as a source of food among hunter- gatherers. The wild grains, fruits, nuts, vegetables, and small animals gathered by women probably constituted the more reliable components of the Paleolithic diet. Moreover, because women were often encum- bered by helpless infants, they probably invented disposable digging sticks and bags in which to carry and store food.
The transition to a new pattern of food production through farming
and animal husbandry is known as the Neolithic Revolution. Neolithic or New Stone Age peoples developed crafts, such as basket-making, pot- tery, spinning, and weaving. Although no art work of this period seems as spectacular as the Paleolithic cave paintings in France and Spain, Neolithic people produced interesting sculptures, ﬁgurines, and pottery.
While archeologists and anthropologists were once obsessed with the when and where of the emergence of an agricultural way of life, they are now more concerned with the how and why. Nineteenth-century anthropologists tended to classify human cultures into a series of ascending, progressive stages marked by the types of tools manufac- tured and the means of food production. Since the 1960s new analytical techniques have made it possible to test hypotheses about environmen- tal and climatic change and their probable effect on the availability of food sources. When the idea of progress is subjected to critical analysis rather than accepted as inevitable, the causes of the Neolithic trans- formation are not as clear as previously assumed. Given the fact that hunter-gatherers may enjoy a better diet and more leisure than agricul- turalists, prehistoric or modern, the advantages of a settled way of life are obvious only to those who are already happily settled and well fed. The food supply available to hunter-gatherers, while more varied than the monotonous staples of the agriculturalist, might well be precarious and uncertain.
Recent studies of the origins of agriculture suggest that it was almost universally adopted between ten thousand and two thousand years ago, primarily in response to pressures generated by the growth of the human population. When comparing the health of foragers and settled farmers, paleopathologists generally ﬁnd that dependence on a speciﬁc crop resulted in populations that were less well nourished than hunter- gatherers, as indicated by height, robustness, dental conditions, and so forth. In agricultural societies, the food base became narrower with dependence on a few or even a single crop. Thus, the food supply might have been adequate and consistent in terms of calories, but deﬁcient in vitamins and minerals. Domestication of animals, however, seemed to improve the nutritional status of ancient populations. Although the total human population apparently grew very slowly prior to the adoption of farming, it increased quite rapidly thereafter. Prolonged breast feeding along with postpartum sexual prohibitions found among many nomadic societies may have maintained long intervals between births. Village life led to early weaning and shorter birth intervals.
The revolutionary changes in physical and social environment associated with the transition from the way of life experienced by small mobile bands of hunter-gatherers to that of sedentary, relatively dense populations also allowed major shifts in patterns of disease. Permanent dwellings, gardens, and ﬁelds provide convenient niches for parasites, insects, and rodents. Stored foods are likely to spoil, attract pests, and become contaminated with rodent excrement, insects, bacteria, molds, and toxins. Agricultural practices increase the number of calories that can be produced per unit of land, but a diet that overemphasizes grains and cereals may be deﬁcient in proteins, vitamins, and minerals.
Lacking the mobility and diversity of resources enjoyed by hunters
and gatherers, sedentary populations may be devastated by crop fail- ures, starvation, and malnutrition. Migrations and invasions of neigh- boring or distant settlements triggered by local famines may carry parasites and pathogens to new territories and populations. Ironically, worrying about our allegedly unnatural and artiﬁcial modern diet has become so fashionable that people in the wealthiest nations have toyed with the quixotic idea of adopting the dietary patterns of ancient humans or even wild primates. In reality, the food supply available to prehistoric peoples was more likely to be inadequate, monotonous, coarse, and unclean.
world. For example, studies of our closest relatives, the great apes and monkeys, have shown that living in a state of nature does not mean freedom from disease. Wild primates suffer from many disorders, including arthritis, malaria, hernias, parasitic worms, and impacted teeth. Our ancestors, the ﬁrst ‘‘naked apes,’’ presumably experienced disorders and diseases similar to those found among modern primates during a lifespan that was truly ‘‘nasty, brutish, and short.’’ Neverthe- less, prehistoric peoples gradually learned to adapt to harsh environ- ments, quite unlike the mythical Garden of Eden. Eventually, through cultural evolution, human beings changed their environment in unprece- dented ways, even as they adapted to its demands. By the domestication of animals, the mastery of agricultural practices, and the creation of densely populated settlements, human beings also generated new patterns of disease.
Paleopathologists must use a combination of primary and second-
ary evidence in order to draw inferences about prehistoric patterns of disease. Primary evidence includes bodies, bones, teeth, ashes, and charred or dried remains of bodies found at sites of accidental or inten- tional human burials. Secondary sources include the art, artifacts, and burial goods of preliterate peoples, and ancient documents that describe or suggest the existence of pathological conditions. The materials for such studies are very fragmentary, and the over-representation of the hard parts of bodies—bones and teeth—undoubtedly distorts our por- trait of the past.
Indeed the possibility of arriving at an unequivocal diagnosis through the study of ancient remains is so small that some scholars insist that the names of modern diseases should never be conferred on ancient materials. Other experts have systematically cataloged paleo- lithic ailments in terms of congenital abnormalities, injury, infection, degenerative conditions, cancers, deﬁciency diseases, and that all-too- large category, diseases of unknown etiology.
Nevertheless, by combining a variety of classical and newly emerg-
ing techniques, scientists can use these fragmentary materials to gain new insights into the patterns of ancient lives. The study of human remains from archaeological contexts may also be referred to as bio- archaeology, a ﬁeld that encompasses physical anthropology and archaeology.
Funerary customs, burial procedures, and environmental con- ditions, such as heat, humidity, soil composition, can determine the state of preservation of human remains. Cremation, in particular, could create severe warping and fragmentation of the remains. Bodies might be buried in the ground shortly after death, covered with a mound of rocks (cairn burial), or placed on a scaffold and exposed to the elements. Both nomadic and settled people might place a body in some type of scaffold as a temporary measure if the death occurred when the ground
was frozen. Later, the skeletal remains could be interred with appro- priate ceremonies. In some cemeteries the dead might be added to old graves, causing the commingling of bones. Added confusion arises from ritual mutilation of the body, the admixture of grave goods and gifts, which may include body parts of animals or grieving relatives, and dis- tortions due to natural or artiﬁcial mummiﬁcation. Burrowing animals and looters might also disturb burial sites and change the distribution of bones. Catastrophes, such as ﬂoods, earthquakes, landslides, and mas- sacres, may provide information about a large group of individuals during one moment in time.
Despite the increasing sophistication and power of the new analyti-
cal techniques employed in the service of paleopathology, many uncer- tainties remain, and all results must still be interpreted with caution. Since the last decades of the twentieth century, scientists have exploited new methods, such as DNA ampliﬁcation and sequencing, the analysis of stable isotopes of carbon and nitrogen, and scanning electron microscopy in order to ask questions about the health, lifestyle, and culture of ancient peoples. Scanning electron microscopy has been used to examine patterns of tooth wear and enamel defects caused by stress and growth disruption, and the effect of workload on the structure of limb bones. Where possible, chemical investigations of trace elements extracted from ancient bones and hair can provide insights into ancient dietary patterns and quality of life. Lead, arsenic, mercury, cadmium, copper, and strontium are among the elements that can be identiﬁed in hair.
The analysis of stable isotopes of carbon and nitrogen provides
insights into bone chemistry and diet, because the ratios of the stable isotopes of carbon and nitrogen found in human and animal remains reﬂect their ratios in the foods consumed. Thus, the relative importance of plant and animal foods in the diet of prehistoric populations can be estimated. Differences in ratios found in human bones for different time periods may reveal changes in diet. For example, scientists determined the relative amounts of carbon 13 and nitrogen 15 in the bones of human beings living in various parts of Europe more than twenty thousand years ago. These studies suggested a diet that was high in ﬁsh, shellﬁsh, and waterfowl. Analyses of the isotopes in the bones of Neanderthals, in contrast, suggested that their dietary proteins came largely from the ﬂesh of larger prey animals.
Today, and presumably in the past, most infections involved soft
tissue rather than bones, but bones and teeth are the primary source of paleopathological information. Scientists can subject skeletal remains to X-rays, CT (computer tomographic) imaging, chemical analysis, and so forth. The bones may reveal evidence about an individual’s history of health and disease, age and cause of death.
Speciﬁc injuries identiﬁable in ancient remains included fractures, dislocations, sprains, torn ligaments, degenerative joint disease, ampu- tations, penetrating wounds, bone spurs, calciﬁed blood clots, nasal septal deformities, and so forth. Projectile weapons, such as spears and arrows, have been found in fossilized vertebrae, sternum, scapula, humerus, and skulls. But projectile tips embedded in bone are rare, either because healers extracted them, or, most likely, the projectile point that caused a fatal injury lodged in soft tissues. In some cases long-term sur- vival occurred after penetrating wounds, as indicated by projectile parts that were incorporated into the injured bone and retained as inert foreign objects.
In favorable cases, the type of injury and the length of time that
elapsed between the traumatic event and death can be estimated. Bones usually heal at relatively predictable rates. Survival and healing suggest some form of treatment, support, and care during convalescence. Some skeletons exhibit fractures that resulted in deformities that must have caused difﬁculty in walking, chronic pain, and degenerative joint dis- ease. The fact of survival suggests the availability of effective assistance during convalescence and after recovery. During healing, bone is usually replaced by bone. Sometimes, however, healing is faulty; complications include osteomyelitis, delayed or nonunion, angular deformities, bone spurs in adjacent soft tissues, calciﬁed blood clots, growth retardation, aseptic necrosis, pseudoarthrosis (ﬁbrous tissue is substituted for bone), and degenerative joint disease (traumatic arthritis).
Bone is a dynamic living tissue constantly being modiﬁed in response to the stimulus of growth, and to physiological and pathologi- cal stresses. Many factors, such as age, sex, nutrition, hormones, heredity, and illness, affect the bones. Heavy labor or vigorous exercise can result in increases in bone mass. Degenerative processes change the size, shape, and conﬁguration of the skeleton and its individual bones. The skeleton can be modiﬁed by inﬂammation of the joints (arthritis) and by decreases in bone density (osteoporosis).
Bones respond to changes in their environment, especially the
mechanical environment created by body weight and muscle forces. The morphology of a bone, therefore, records the mechanical forces exerted on it during life. Usually, paleopathologists are interested in bones that display obvious pathology, but normal bones can provide evidence of body size, behavior, degree of sexual dimorphism, activities, workloads, and posture. Bones may, therefore, testify that an individual habitually performed heavy lifting, pushing, pulling, carrying, standing, stooping, walking, running, or squatting. For example, a peculiarity of the ankle joint, known as a squatting facet, is found in people who spend much of their times in a squatting position. Thus, the absence of squatting facets distinguishes those who sat in chairs from those who did not.
Most diseases do not leave speciﬁc signs in the skeleton, but tuberculosis, yaws, syphilis, and some fungal infections may leave diag- nostic clues. Twentieth century studies suggest that the skeleton is affected in about one to two percent of tuberculosis patients. The kinds of bone lesions caused by syphilis are generally different from those caused by tuberculosis. Congenital syphilis may produce the so-called Hutchinson’s incisor defect. Leprosy often results in damage to the bones of the face, ﬁngers, and toes. Because hormones regulate the growth and development of all parts of the body, a malfunction of the endocrine glands may leave signs in the bones. Some peculiarities in ancient skeletal remains have been attributed to abnormalities of the pituitary and thyroid glands. However, because of recent changes in patterns of disease, physicians, unlike paleopathologists, rarely see the results of historically signiﬁcant severe, untreated infectious diseases. Various cancers may be identiﬁable in skeletal remains. Although primary bone cancers are probably rare, many other cancers may spread to the bone. Some relatively uncommon conditions, such as osteomyelitis and various benign tumors of the bone and cartilage, have been of particular interest to paleopathologists because they are easily recognized.
Various forms of malnutrition, such as rickets, scurvy, and anemia,
may cause abnormalities in the structure of the bone (porotic hyperos- tosis). Rickets was rare during Neolithic times, but became increasingly common as towns and cities grew. Osteomalacia, an adult form of rick- ets, can cause collapse of the bones of the pelvis, making childbirth a death sentence for mother and fetus. The presence of calciﬁed blood clots in many skeletons might reﬂect the prevalence of scurvy in a particu- lar population. Given heavy or chronic exposure, some soil elements, such as arsenic, bismuth, lead, mercury, and selenium, can cause toxic effects that leave their mark on the bones. Porotic hyperostosis is a pathological condition characterized by porous, sieve-like lesions that are found in ancient human skulls. These lesions may be caused by mal- nutrition and infectious diseases—iron deﬁciency anemia or inﬂam- matory processes, bleeding associated with scurvy, or certain diseases (rickets, tumors). Generally, it is difﬁcult to determine the speciﬁc cause of such defects. Moreover, postmortem damage can simulate these conditions.
Although tooth decay and cavities are often thought of as the results of a modern diet, studies of contemporary primitives and research on ancient skeletons disprove this assumption. Dental problems and dis- eases found in human remains include dental attrition due to diet, temporomandibular joint derangement, plaque, caries, abscesses, tooth crown fractures, tooth loss, and so forth. Analysis of dental microwear patterns by scanning electron microscopy and microwear measurements began in the 1980s. Microscopic pits, scratches on tooth surfaces, and
surface attrition reveal patterns of wear caused by abrasive particles in food. Abrasive wear could lead to infection and tooth loss. Dental dis- orders were often worse in women, because of the effects of pregnancy and lactation, and the use of teeth and jaws as tools.
In general, the condition of bones and teeth provides a history of health and disease, diet and nutritional deﬁciencies, a record of severe stresses or workload during life, and an approximate age at death. Bone fractures provide a record of trauma, which might be followed by infection or by healing. Before the ﬁnal closure of the epiphyses, the growing bones are vulnerable to trauma, infections, and growth disorders. Stresses severe enough to disrupt growth during childhood result in transverse lines, usually called Harris lines or growth arrest lines, which are visible in radiographs of the long bones of the body. Because Harris lines suggest severe but temporary disturbance of growth, a population suffering from chronic malnutrition has fewer transverse lines than one exposed to periodic or seasonal starvation. Starvation, severe malnutrition, and severe infection may also leave characteristic signs in the teeth, microdefects in dental enamel known as pathological striae of Retzius, enamel hypoplasias, or Wilson bands. Severe episodes of infant diarrheas, for example, can disrupt the devel- opment of teeth and bones. Scanning electron micrography makes it possible to observe disruptions in the pattern of these lines, but there is still considerable uncertainty about the meaning of pathological striae of Retzius.
Archaeological chemistry, the analysis of inorganic and organic materials, has been used in the discovery, dating, interpretation, and authentication of ancient remains. This approach provides many ways of reconstructing ancient human cultures from bits of stone tools, ceramics, textiles, paints, and so forth. By combining microscopy with chemical analysis, scientists can recover information about the manu- facture and use of ancient artifacts because such objects carry with them a ‘‘memory’’ of how they were manipulated in the past. Perhaps the most familiar aspect of archaeological chemistry is the carbon-14 method for dating ancient remains. Carbon-14 dating is especially valuable for studying materials from the last ten thousand years, the period during which the most profound changes in cultural evolution occurred.
Multidisciplinary groups of scientists have combined their expertise in archaeology, chemistry, geophysics, imaging technology, and remote sensing as a means of guiding nondestructive investigations of sensitive archeological sites. As the techniques of molecular biology are adapted to the questions posed by paleopathologists, new kinds of information can be teased out of the surviving traces of proteins and nucleic acids found in some ancient materials. Improvements in instrumentation allow archaeologists to analyze even smaller quantities of biological materials. For example, by using mass spectrometry and lipid bio- markers chemists can distinguish between human and other animal remains.