DISEASE IN HUMAN EVOLUTION: THE RE-EMERGENCE OF INFECTIOUS DISEASE IN THE THIRD EPIDEMIOLOGICAL TRANSITION

DISEASE IN HUMAN EVOLUTION: THE RE-EMERGENCE OF INFECTIOUS DISEASE IN THE THIRD EPIDEMIOLOGICAL TRANSITION

by George J. Armelagos, Kathleen C. Barnes, and James Lin

For millions of years, humans and their ancestors suffered from diseases -- both the kind caused by infectious pathogens (e.g., bacteria, viruses, parasites) and the kind caused by our own bodies as they age and degenerate. Over this long period, humans constantly created new ways of living and eating, and actual physical or genetic changes evolved to minimize the effects of these diseases. From the point of view of a bacteria or virus, however, any shift in the physical makeup or behavior of its human host represents not only an obstacle but also a challenge to be overcome. As a result, new diseases emerged with each major change in the human way of life.
For nearly four million years, humans lived in widely dispersed, nomadic, small populations that minimized the effect of infectious diseases. With the agricultural revolution about 10,000 years ago, increasing sedentism and larger population groupings resulted in the first epidemiological transition in which infectious and nutritional diseases increased. Within the last century, with the advent of public health measures, improved nutrition and medicine, some populations in developed nations underwent a second epidemiological transition. During this transition, infectious diseases declined and non-infectious, chronic diseases, and degenerative conditions increased. Today, with the increasing use of antibiotics, we are facing a third epidemiological transition, a reemergence of infectious disease, with pathogens that are antibiotic-resistant and have the potential to be transmitted on a global scale. Populations that experienced and those that never experienced the second epidemiological transition are both increasingly exposed to antibiotic-resistant pathogens.

"Emerging" pathogens are seen as new diseases, discovered when they have an impact on our adaptation or survival. Even when we take a more holistic ecological perspective, it is often limited to a position that considers emerging disease as the result of environmental changes that are only relevant to the present situation as it affects humans here and now. This article argues that the emergence of new diseases has been the human pattern since the origin of the hominids and accelerated with the shift to agriculture 10,000 years ago.

Paleolithic Baseline
For most of their 4,000,000 years of evolutionary history, human populations lived in small, sparsely settled groups. Population size and density remained low throughout the Paleolithic. Fertility and mortality rates in small gathering-hunting populations would have to have been balanced for the population size to remain small.

Demographic factors creating this stability are still a matter of discussion. Some demographers argue that gatherer-hunters were at their maximum natural fertility, balanced by high mortality. Armelagos, Goodman and Jacobs (1991) argue, however, that gatherer-hunters maintained a stable population with controlled moderate fertility balanced by moderate mortality.

The demographic changes following the Neolithic may provide insights into the case for population stability controlled by moderate fertility and mortality during the Paleolithic. Following the Neolithic revolution, a dramatic increase in population size and density occurred. It was thought that the Neolithic economy generated food surpluses that led to a better nourished and healthier population with a reduced rate of mortality. Since populations were at their natural maximum fertility, there would have been a rapid increase in population size.

The empirical evidence suggests an alternative scenario in the shift from gathering and hunting to agriculture. The picture suggests a much bleaker picture of health. Instead of experiencing improved health, there is evidence of a substantial increase in infectious and nutritional disease (Cohen and Armelagos 1984). A paradox emerges if the traditionally accepted models of Paleolithic fertility and mortality are correct. How can a population experiencing maximum fertility during the Paleolithic respond with exponential growth in population when their health is deteriorating?

A consideration of the disease ecology of contemporary gatherer-hunters provides insights into the types of disease that probably affected our gatherer-hunter ancestors. Polgar (1964) suggests that gatherer-hunters had two types of disease to contend with in their adaptation to their environment. One class of disease would be those organisms that had adapted to prehominid ancestors and persisted with them as they evolved into hominids. Head and body lice (Pediculus humanus), pinworms, yaws, and possibly malaria would be included in this group. Cockburn (1967) adds to this list most of the internal protozoa found in modern humans and such bacteria as salmonella, typhi, and staphylococci.

The second class of diseases are the zoonotic, which have non-human animals as their primary host and only incidentally infect humans. Humans can be infected by zoonoses through insect bites, by preparation and consumption of contaminated flesh, and from wounds inflicted by animals. Sleeping sickness, tetanus, scrub typhus, relapsing fever, trichinosis, tularemia, avian or ichthyic tuberculosis, leptospirosis, and schistosomiasis are among the zoonotic diseases that could have afflicted earlier gatherer-hunters (Cockburn 1971).

Although early human populations were too small to support endemic (constantly present) pathogens, they maintained some kind of relationships with the vectors that would later serve to perpetuate such human host-specific diseases as yellow fever and louse-borne relapsing fever. Certain lice were ectoparasites as early as the Oligocene, and the prehumans of the early Pliocene probably suffered from malaria, since the Anopheles (mosquito) necessary for transmission of the disease evolved by the Miocene era. Frank Livingstone, an anthropological epidemiologist, dismisses, however, the potential of malaria in early hominids except in isolated incidences because of the small population size and an adaptation to the savanna, an environment that would not have included the mosquitoes that carry the malaria plasmodium.

The range of the earliest hominids was probably restricted to the tropical savanna. This would have limited the pathogens that were potential disease agents. During the course of human evolution, the habitat expanded gradually into the temperate and eventually the tundra zones. Hominids, according to epidemiologist Frank Lambrecht, would have avoided large areas of the African landscape because of tsetse flies and thus avoided the trypanosomes they carried. He also argues that the evolution of the human species and its expansion into new ecological niches would have led to a change in the pattern of trypanosome infection. While this list of diseases that may have plagued our gathering-hunting ancestors is informative, those diseases that would have been absent are also of interest. The contagious community diseases such as influenza, measles, mumps, and smallpox would have been missing. There probably would have been few viruses infecting these early hominids, although Cockburn (1967) disagrees and suggests that the viral diseases found in non-human primates would have been easily transmitted to hominids.

The First Epidemiological Transition: Disease in Agricultural Populations
The reliance on primary food production (agriculture) increased the incidence and the impact of disease. Sedentism, an important feature of agricultural adaptation, conceivably increased parasitic disease spread by contact with human waste. In gathering-hunting groups, the frequent movement of the base camp and frequent forays away from the base camp by men and women would decrease their contact with human wastes. In sedentary populations, the proximity of habitation area and waste deposit sites to the water supply is a source of contamination. While sedentarism did occur prior to the Neolithic period in those areas with abundant resources, once there was the shift to agriculture, sedentary living was necessary.

The domestication of animals provided a steady supply of vectors and greater exposure to zoonotic diseases. The zoonotic infections most likely increased because of domesticated animals, such as goats, sheep, cattle, pigs, and fowl, as well as the unwanted domestic animals such as rodents and sparrows, which developed (Polgar 1964) permanent habitats in and around human dwellings. Products of domesticated animals such as milk, hair, and skin, as well as the dust raised by the animals, could transmit anthrax, Q fever, brucellosis, and tuberculosis. Breaking the sod during cultivation exposed workers to insect bites and diseases such as scrub typhus. Frank Livingstone showed that slash-and-burn agriculture in west Africa exposed populations to Anopheles gambiae, a mosquito which is the vector for Plasmodium falciparum, which causes malaria. Agricultural practices also create pools of water, expanding the potential breeding sites for mosquitos. The combination of disruptive environmental farming practices and the presence of domestic animals also increased human contact with arthropod (insect) vectors carrying yellow fever, trypanosomiasis, and filariasis, which then developed a preference for human blood. Some disease vectors developed dependent relationships with human habitats, the best example of which is Aedes aegypti (vector for yellow fever and dengue), which breeds in stagnant pools of water in open containers. Various agricultural practices increased contact with non-vector parasites. Irrigation brought contact with schistosomal cercariae, and the use of feces as fertilizer caused infection from intestinal flukes (Cockburn 1971).

The shift to agriculture led to a change in ecology; this resulted in diseases not frequently encountered by forager populations. The shift from a varied, well-balanced diet to one which contained fewer types of food sometimes resulted in dietary deficiencies. Food was stored in large quantities and widely distributed, probably resulting in outbreaks of food poisoning. Intensive agricultural practices among the prehistoric Nubians resulted in iron deficiency anemia as did the reliance on cereal grain, weaning practices, and parasitic infestation. The combination of a complex society, increasing divisions of class, epidemic disease, and dietary insufficiencies no doubt added mental stress to the list of illnesses.

Disease in Urban Populations
The development of urban centers is a recent development in human history. In the Near East, cities as large as 50,000 people were established by 3000 BC. In the New World, large urban settlements were in existence by AD 600. Settlements of this size increase the already difficult problem of removing human wastes and delivering uncontaminated water to the people. Cholera, which is transmitted by contaminated water, was a potential problem. Diseases such as typhus (carried by lice) and the plague bacillus (transmitted by fleas or by the respiratory route) could be spread from person to person. Viral diseases such as measles, mumps, chicken pox, and smallpox could be spread in a similar fashion. Due to urbanization, populations for the first time were large enough to maintain disease in an endemic form. Aidan Cockburn, a paleopathologist, estimated that populations of one million would be necessary to maintain measles as an endemic disease. What was an endemic disease in one population could be the source of a serious epidemic (affecting a large number of people at the same time) disease in another group. Cross-continental trade and travel resulted in intense epidemics (McNeill 1976). The Black Death, resulting from a new pathogen, took its toll in Europe in the 1300s; this epidemic eliminated at least a quarter of the European population (approximately 25 million people).

The period of urban development can also be characterized by the exploration and expansion of populations into new areas that resulted in the introduction of novel diseases to groups that had little resistance to them (McNeill 1976). For example, the exploration of the New World may have been the source of the treponemal infection (syphilis) that was transmitted to the Old World. This New World infection was endemic and not sexually transmitted. When it was introduced into the Old World, a different mode of disease transmission occurred. The sexual transmission of the treponeme created a different environment for the pathogen, and it resulted in a more severe and acute infection. Furthermore, crowding in the urban centers, changes in sexual practices, such as prostitution, and an increase in sexual promiscuity may have been factors in the venereal transmission of the pathogen.

The process of industrialization, which began a little over 200 years ago, led to an even greater environmental and social transformation. City dwellers were forced to contend with industrial wastes and polluted water and air. Slums that arose in industrial cities became focal points for poverty and the spread of disease. Epidemics of smallpox, typhus, typhoid, diphtheria, measles, and yellow fever in urban settings were well documented. Tuberculosis and respiratory diseases such as pneumonia and bronchitis were even more serious problems, with harsh working situations and crowded living conditions. Urban population centers, with their extremely high mortality, were not able to maintain their population bases by the reproductive capacity of those living in the city. Mortality outstripped fertility, requiring immigration to maintain the size of the population.

The Second Epidemiological Transition: The Rise of Chronic and Degenerative Disease
The second epidemiological transition refers to the shift from acute infectious diseases to chronic non- infectious, degenerative diseases. The increasing prevalence of these chronic diseases is related to an increase in longevity. Cultural advances results in a larger percentage of individuals reaching the oldest age segment of the population. In addition, the technological advances that characterize the second epidemiological transition resulted in an increase in environmental degradation. An interesting characteristic of many of the chronic diseases is their particular prevalence and 'epidemic'-like occurrence in transitional societies, or in those populations undergoing the shift from developing to developed modes of production. In developing countries, many of the chronic diseases associated with the epidemiological transition appear first in members of the upper socioeconomic strata, because of their access to Western products and practices.

With increasing developments in technology, medicine, and science, the germ theory of disease causation developed. While there is some controversy about the role that medicine has played in the decline of some of the infectious diseases, a better understanding of the source of infectious disease exists, and this admittedly has resulted in increasing control over many infectious diseases. The development of immunization resulted in the control of many infections and recently was the primary factor in the eradication of smallpox. In the developed nations, a number of other communicable diseases have diminished in importance. The decrease in infectious disease and the subsequent reduction in infant mortality has resulted in greater life expectancy at birth. In addition, there has been an increase in longevity for adults and this has resulted in an increase in chronic and degenerative diseases.

Many of the diseases of the second epidemiological transition share common etiological factors related to human adaptation, including diet, activity level, mental stress, behavioral practices, and environmental pollution. For example, the industrialization and commercialization of food often results in malnutrition, especially for those societies in "transition" from subsistence forms of food provision to agribusiness. The economic capacity to purchase food that meets nutritional requirements is often not possible. Obesity and high intakes of refined carbohydrates are related to the increasing incidence of heart disease and diabetes. Obesity is considered to be a common form of malnutrition in developed countries and is a direct result of an increasingly sedentary lifestyle in conjunction with steady or increasing caloric intakes.

A unique characteristic of the chronic diseases is their relatively recent appearance in human history as a major cause of morbidity. This is indicative of a strong environmental factor in disease etiology. While biological factors such as genetics are no doubt important in determining who is most likely to succumb to which disease, genetics alone cannot explain the rapid increase in chronic disease. While some of our current chronic diseases such as osteoarthritis were prevalent in early human populations, other more serious degenerative conditions such as cardiovascular disease and carcinoma were much rarer.

The Third Epidemiological Transition
Today, human populations are moving into the third epidemiological transition. There is a reemergence of infectious diseases with multiple antibiotic resistance. Furthermore, this emergence of diseases has a potential for global impact. In a sense, the contemporary transition does not eliminate the possible co-existence of infectious diseases typical of the first epidemiological transition (some 10,000 years ago) in our own time; the World Health Organization (WHO) reports that of the 50,000,000 deaths each year, 17,500,000 are the result of infectious and parasitic disease. WHO reports that 1.7 million have tuberculosis and 30 million people are infected with HIV.

The emergence of infectious disease has been one of the most interesting evolutionary stories of the last decade, and has captured the interest of scientists and the public. The popular media, with the publication of books such as The Hot Zone and movies such as Outbreak, has captured the public's fascination with emerging diseases as threats to human survival. There is genuine scientific concern about the problem. David Satcher (Director of the Centers for Disease Control in Atlanta, GA) lists 22 diseases that have emerged in the last 22 years, including Rotovirus, Ebola virus, Legionella pneumophila (Legionnaire s Disease), Hantaan Virus (Korean hemorrhagic fever), HTLV I, Staphylococcus toxin, Escherichia coli 0157:h7, HTLV II, HIV, Human Herpes Virus 6, Hepatitis C, and Hantavirus isolates.

The emergence of disease is the result of an interaction of social, demographic, and environmental changes in a global ecology and in the adaptation and genetics of the microbe, influenced by international commerce and travel, technological change, breakdown of public health measures, and microbial adaptation. Ecological changes such as agricultural development projects, dams, deforestation, floods, droughts and climatic changes have resulted in the emergence of diseases such as Argentine hemorrhagic fever, Korean hemorrhagic fever (Hantaan) and Hantavirus pulmonary syndrome. Human demographic behavior has been a factor in the spread of dengue fever, and the source for the introduction and spread of HIV and other sexually transmitted diseases.

The engine that is driving the reemergence of many of the diseases is ecological change that brings humans into contact with pathogens. Except for the Brazilian pururic fever, which may represent a new strain of Haemophilus influenzae, biotype aegyptius, most of the emerging diseases are of cultural origin. The development of antibiotic resistance in any pathogen is the result of medical and agricultural practices. The indiscriminate and inappropriate use of antibiotics in medicine has resulted in hospitals that are the source of multi-drug resistant strains of bacteria that infect a large number of patients. Agricultural use in which animal feed is supplemented with sub-therapeutic doses of antibiotics has risen dramatically in the last half century. In 1954, 500,000 pounds of antibiotics were produced in the United States; today, 40,000,000 pounds are produced annually.

Conclusion
Recently, much attention has focused on the detrimental effects of industrialization on the international environment, including water, land, and atmosphere. Massive industrial production of commodities has caused pollution. Increasingly there is concern over the health implications of contaminated water supplies, over-use of pesticides in commercialized agriculture, atmospheric chemicals, and the future effects of a depleted ozone layer on human health and food production. At no other time in human history have the changes in the environment been more rapid or so extreme. Increasing incidence of cancer among young people and the increase in respiratory disease has been implicated in these environmental changes.

Anthropogenic impact from technology has been the pattern since Neolithic times. Within the last 300 years, transportation has played a major role in disease patterns by bringing larger segments of humans into contact with the pathogens at an accelerated rate. The emergence of disease in the New World upon contact with Europeans was a consequence of large sailing ships that became a major mode of transportation. Now it is possible for a pathogen to move between continents within a matter of hours. We live in a time where there exists a virtual viral superhighway, bringing people into contact with pathogens that affect our adaptation. The present pattern reflects an evolutionary trend that can be traced to the beginning of primary food production. The scale has changed. The rates of emerging disease and their impact can now affect large segments of the world population at an ever increasing rate, and we need to be increasingly aware of the implications for today s human populations around the globe.

For further reading
Armelagos, G. J. Human evolution and the evolution of human disease. Ethnicity and Disease 1(1): 21-26, 1991.
Armelagos, G. J., A. H. Goodman, et al. The origins of agriculture: Population growth during a period of declining health. Population and Environment 13(1): 9-22, 1991.
Cockburn, T. A. The evolution of human infectious diseases. In Infectious Diseases: Their Evolution and Eradication, T. A. Cockburn, ed. Springfield, IL: Charles C. Thomas, 1967.
Cockburn, T. A. Infectious disease in ancient populations. Current Anthropology 12(1): 45-62, 1971.
Cohen, M. N. and G. J. Armelagos, eds. Paleopathology at the Origin of Agriculure. Orlando: Academic Press, 1984.
Ewald, P. W. Evolution of Infectious Disease. New York: Oxford University Press, 1994.
McNeill, W. H. Plagues and People. Garden City: Anchor/Doubleday, 1976.
Polgar, S. Evolution and the ills of mankind. In Horizons of Anthropology, Sol Tax, ed. Chicago: Aldine, 1964.

George Armelagos is professor of anthropology at Emory University in Atlanta, Georgia. He received his Ph.D. from the University of Colorado in 1968, and his research has focused on diet and disease in human adaptation. A former President of the American Association of Physical Anthropologists, he has authored or co-authored more than 120 books and articles, including Disease in Populations in Transition: Anthropological and Epidemiological Perspective (with Alan Swedlund) and Consuming Passions: The Anthropology of Eating (with Peter Farb).

Kathleen C. Barnes is an instructor at The Johns Hopkins Center for Asthma and Allergy in Baltimore, Maryland. She received her Ph.D. in Anthropology from the University of Florida, Gainesville in 1992 after working as a registered nurse for several years. Her interests include health and disease in the Caribbean.

James Lin is an anthropology and human biology major at Emory University who is interested in health policy research. He plans on entering a MD-PhD program after spending a research year in Japan.

MORTUARY CUSTOMS AND THE BELIEF IN SURVIVAL AFTER DEATH AMONG THE SOUTH-EASTERN BANTU

MORTUARY CUSTOMS AND THE BELIEF IN SURVIVAL AFTER DEATH AMONG THE SOUTH-EASTERN BANTU

By MAX GLUCKMANN

The belief in survival after death is not a response of the individual to death. It is accepted as part of his heritage and must therefore be related to mortuary and other social customs. Social anthropologists who explain it entirely by the emotional comfort it gives to the dying person and his survivors 2 avoid many of the important problems involved. Typical statements such as that by believing in his immortality man "never has to come to an impasse and his hope will hurdle death itself," 3 or that in the "conflict and chaos" of death religion "standardises the comforting, the saving belief," 4 are very facile explanations. Unloved parents are buried with full ceremony; strangers have special funerals; people dying away from home may be buried by proxy. The emotions expressed at a funeral may have no relation to the emotions actually felt. Thus Miss Hunter tells us of the Mpondo that "women are not expected to make a fuss and weep after a child is buried ....., but the fact that they are composed does not mean that they do not feel the loss bitterly." 5 Mortuary customs impose on the survivors not only certain modes of behaviour but also the simulation of certain emotions which may or may not be felt. Thus the statements of Wallis and Malinowski may describe the emotional satisfaction derived on occasion from a funeral but they do not advance a sociological understanding of all mortuary customs and beliefs. I propose in the following analysis to indicate what seems to me some of the major problems, chiefly by reference to Junod's account of the Thonga of Portuguese East Africa.

According to the South Eastern Bantu it is either a man's shadow or breath which becomes his ghost after death. This ghost figures in the ritual beliefs and practices of these Bantu. Two other things are also made the subject of ritual. Firstly there is his body which must be disposed of in some way. Secondly there is what Radcliffe-Brown calls his social personality, "the sum of characteristics by which he has an effect upon the social life and therefore on the social sentiments of others. ...... A person occupies a definite position in society, has a certain share in the social life, and is one of the supports of the network of social relations." He goes on to say that "death constitutes a partial destruction of the social cohesion, the normal social life is disorganised, the social equilibrium is disturbed. After the death the society has to organise itself anew and reach a new condition of equilibrium." 6 I do not like the manner in which Radcliffe-Brown has described this readjustment of social relationships, but he makes clear that the mortuary customs as modes of social behaviour are concerned not with the dead man's own individual personality or his personal relations with his survivors. They deal with his social personality, the ideal position which he occupied in the society. The relation of these two personalities is another problem.

I shall later expand on this point. Now I wish to point out that Radcliffe-Brown also loses himself in the emotional interpretation when he says that "we may translate the above statement into terms of personal feeling by saying that the death removes a person who was the object of feelings of affection and attachment on the part of the others and is thus a direct offence against those sentiments in the survivors."

"Though the dead man has ceased to exist as a member of society, it is clear that he has by no means ceased to influence the society. On the contrary, he becomes the source of intense painful emotions." 7 I stress this point again because this type of explanation is frequent to-day. Ritual and mystical beliefs determine the emotional reaction of a particular people to a certain situation and therefore one cannot explain the reaction by the emotion expressed. Radcliffe-Brown's last quoted statement will not cover the rejoicing of the Thonga if a man is killed by lightning or the orgies of mourning which Shaka forced on his subjects after his mother's death.

Radcliffe-Brown has described the survival of the social personality; he has not properly elaborated his thesis. When a man dies his death breaks off a number of social relationships. During is life he was related to a large number of people in different ways and these relationships were determined by certain social rules and expressed in certain modes of behaviour. After his death these relationships are changed and new ones come into being; perhaps also the relationship between his surviving fellows are affected. These vary from one person to another. For different individuals a man to whom was owing a certain social attitude has become a ghost. One person may be the dead man's son, another is a maternal uncle, or a brother, or wife. The the death therefore each of these individuals is required to react differently. It must be remembered that a funeral as recorded by the ethnographer is an abstraction from different people's behaviour. He describes the funerals of headmen, women, children, witch-doctors, etc., always in relation to the dead person. 8 But for purposes of sociological interpretation a further description is required. For a Native life a funeral differs for each kinsman.

In communities such as those of the South-Eastern Bantu 9 where status is determined by consanguineous and affinal relationships every man and woman has his or her rôle in social life fixed by these relationships. On the death of, say, the head of a homestead, the relationships of his cognates and affines are altered. In addition the relationships of his relatives towards each other are affected and are reconstituted in the mortuary customs. For the widows this death means the loss of their husband and they must prepare to start a new life with one of his kinsmen; a brother or son may be succeeding to the headship of the homestead and the other male relatives becoming subordinate to him; his children lose their father, relatives of the widows their link with their affines, his uterine nephews perhaps their special connection with their mothers' kin. A different social situation exists for each of them. The ritual of death ceremonies provides them with a social reaction to this situation adapted to their special relationship to the dead man. Outside of their own ritual behaviour they may see the funeral as a whole: but in the readjustment of social relationships each participant has to observe his own prescribed rules of behaviour. At one funeral these will vary from relative to relative, for one individual they will vary from the funeral of one relative to another.

For a full understanding of mortuary customs we require detailed information on these prescribed rules of behaviour. Unfortunately it is not available. Thus Junod describes the part of various relatives in a long series of rites. He does not trace the connection in their behaviour through the whole series. Of course this behaviours is related to that of others at the same time but it is equally related to their own behaviour in preceding and succeeding ritual situations.
I must make one further point. When a man dies his relationships with his fellows are affected by mystical beliefs about the cause of his death; by the actual manner of his death; and by beliefs about death itself. All these elements combine in the complicated death ceremonies. I propose to consider these as they affect the readjustment and reconstitution of social relationships; the disposal of the body; reaction to the mystical causes and forces of death; the life of the ghost in the afterworld and the links of the afterworld with this world.

II
On the death of a family headman various kinship relationships are involved. There are his cognatic relationships with brothers and sons, especially as the death of a family head is often followed by the splitting up of the family which he has held together. Then there are his matrilineal relationships, and his relationship with his wives and their kinsmen. Finally one may consider on this plane his relationship with his dead ascendants, the ancestral spirits of whom he is to become one. In death ceremonies the old relationships are expressed and new one formally initiated and the ritual demands the expression of determined emotions and behaviour much of which is related to these changes in social relationships.

It is by no means certain that one could in the field work out coherently the ritual behaviour of each set of kinspeople. Many other ideas are represented in funeral ceremonies. The task is therefore still more difficult on the data available, but I shall set out suggestions which indicate that some such study might profitably be made.

To begin with one notices in all the South-Eastern Bantu tribes that all relatives must be informed of the death and if possible pay their respects to the dead. Those far away are informed by magic. The Thonga, for example, blow medicines in the direction of the absent person; Mrs. Kuper informs me that Swazi in Johannesburg use purifying medicines if they hear of the death of a relative at home, and that a Zulu in Johannesburg told her that he lost his job because he had not been informed of the death of his child and had not therefore had a chance to purify himself. The food of the homestead is taboo to relatives. They shave their heads and undergo strengthening medications. The essence of the funeral is that it brings together all the kin. I have noted that there is a tendency for families to split on the death of patriarchs. At their funerals this is shown in a ceremonial venting of grievances by all the relatives. The rites themselves stress the family unity, largely in sacrifices which affirm the bond of the survivors, the dead and their common ancestors, and in which the new head of the family first officiates as priest. The Thonga pray that they may live in peace; perhaps they wish that the surviving brothers may not quarrel. The death of the headman upsets the collective life of the homestead which is broken down and abandoned. The Thonga think this collective life is represented by marital sexual relations, and these are suspended for a time, when resumed in ritual intercourse. The purpose of this is stated to be "to cleanse the inheritance" which is primarily succession to the headship of the homestead.

Through all the rites run the expression of group unity. A funeral is the ceremony par excellence which all relatives must attend, lest they be suspected of causing the death by witchcraft. It is too the only ceremony when, if individuals are unavoidably absent, they are brought by proxy into the rites. Their belongings are purified for them and when they do return home they must first ritually eat of food before they can enter the homestead. When Thonga huntsmen return to their homes after a long trip to find that someone has died they and their guns are purified. In the rites of allegiance to the ancestors quarrels must be settled. On this occasion the group often reacts violently against the suspected cause of death (perhaps a wizard); in some Bantu tribes the men brandish their weapons against the spirits. Among the Zulu there is a ritual hunt which on the death of a chief may be turned into a war. In other words the unity of the kinship group or the tribe is additionally expressed in opposition to some enemy outside of it: a wizard (who does not probably in fact exist), the evil spirits, or a hostile tribe.

Of the behaviour of brothers and sons we are told so little that all one can infer is that the brothers who supported the dead man when he was alive have to give him their last office as gravediggers, and, where necessary, support the chief son, the heir, in his ritual observances. Part of the ceremonial is directly to institute the heir and exhort him to behave well. The brothers are magically cleansed and purified for, since death is infectious, they are likely to follow the dead. Even their spears are contaminated; they are cleansed with medicines and, among the Zulu, formally used again in a ritual hunt.

Of the behaviour of affines we are only told by Junod that parents-in-law mourn over their daughters, the new widows, but the first prayer at the grave requests that they will assist in the mourning. The ceremonies in which Thonga matrilineal relatives figures are significant. They have no official part in the burial or the great mourning ceremony; only at the end of the latter does one of the uterine nephews appear to cleanse the food of the deceased. That is, though the patrilineal kin cannot touch the food, they are formally allowed to after this nephew, a kinsman but not of the group, has cleansed it. But this rite is extraneous to the ordinary ritual: it is only in the final family rites that the uterine nephews have an important role. When the family unity is being ritually expressed these nephews sacrifice to the dead man. For some reason his first acceptance of a sacrifice is not from his cognates. And these uterine relatives desecrate the sacrifice by interrupting it and stealing the meat, which is in accord with their normal joking relationship with their maternal uncle when he was alive. Then they could snatch his food from him. Perhaps in this final family rite there is a tendency to assert the integrity of the patrilineal group against these friendly outsiders, or to give sublimated expression to any feelings of relief, hostility to the dead man, etc., the patrilineal relatives may feel. But one can add little to Junod's statement that the nephews can do this because they are "the darlings of the gods." Jacques however maintains that Junod is wrong in saying that bantunkulu are the uterine nephews; he says they are the patrilineal grandsons. Thus it would be the privileged descendants of the headman who treated them freely and lovingly who spoil the sacrifice, and perhaps they sacrifice to include the spirit to care for the descendants he loved.

Most of Junod's information is about the ritual behaviour of the widows. Whatever their feelings they are required to lament most and mourn longest. Their actions are the centre of the great mourning ceremony, which commences with their initiation to the status of widows 10 by those previously widowed. In this initiation the left groin of the widow is cut. The blood represents the husband and if it flows freely marital relationships are considered to have been good. The widow is exposed to medicine smoke and with her urine extinguishes the fire. Now, as a widow, for the last time she passes through her husband's hut. For the next five days the widows are treated by the magician and live outside the village. Some time later there are wild and lascivious dances when the widows, "uncovered by the death of their husband," posture lewdly before the men. 11 The widows do not participate in the ordinary sexual rites of cleansing, but each has to seduce a stranger into intercourse and break off the act ante seminem immissum. The man will die. The widow's intimate associations with the husband were through sex, and she has ritually to pass on the contamination of death to the stranger in intercourse. Then after a preliminary medication she can begin life with the man who inherits her.

Meanwhile the dead man is also moving into a new social status. At a Thonga burial he is introduced to the ancestors as "dead", and in the later rites he is himself sacrificed to. Among the Zulu an old man may be escorted on his way, before even he is dying, with a sacrifice; and when he dies there is little ceremonial as he has merely "gone home". For a time in Native parlance the spirit is thought to wander after burial in the veld, and then to appear in the form of a snake at a final ceremony some months later. Thereafter he has power, varying with his status on earth, to help or punish his own classifactory descendants. The ancestral spirits communicate with the living through diviners and dreams and by sending illness; they give fertility or barrenness, pestilence, rain, good crops.

I have attempted to trace through Junod's description the part played in funeral ceremonies by each set of relatives. Perhaps I may briefly indicate the relation of these parts within each Thonga rite. Before a man's death he is concerned not with the fate of his soul but with settling his affairs on earth. Immediately after his death his body is prepared for burial by his brothers while care is taken to inform all his relatives of the death. Sexual intercourse of married people is taboo. Everybody, and all the man's possessions are contaminated by the death: this notion explains much of the behaviour of readjustment. It seems to arise in the feeling that if one member of the family dies another will follow, and the closer the relationship the greater the danger. Not only are the ancestors invoked to help the family but the magician is called in to strengthen it. This seems to indicate that in Native belief death is ascribed almost always to a mystical force, which continues to operate now that it has its hold in the family and which must be ritually countered. After the death of children and old people whose death is taken as natural there are no such ceremonies. The body is buried reverently and the spirit commended to the ancestors.

In the succeeding rite the widows and grave-diggers (brothers?) are purified and strengthened by the magician; the former are initiated into the status of widows, and while the men hide they pass through the funeral hut for the last time. Then the men take the first steps towards the demolition of the hut. The dances, lewd for women, warlike for men, commence. The homestead, its inhabitants and their implements are medicinally cleaned.

Some time afterwards the married couples ritually resume sexual intercourse and impress their sexual secretions in the village square. After another interval the dead man is sacrificed to and his hut is crushed. There is a reunion which all relatives must attend and at which all grievances must be vented. The new headman is exhorted to rule well. The matrilineal relatives come to assist; they sacrifice and steal the sacrificial meat. Only the widows remain contaminated and they cleanse themselves in intercourse with a stranger.

The above analysis may be applied to the variation of death ceremonies with social status. One must note, however, that there is no mean for funeral rites and variation from it; a death creates a different social situation according to the status, or manner of death, of the deceased, and each funeral involves the participation of different persons behaving in prescribed ways.

In the burial of a Thonga child only the mother who alone has had real social relationships with it plays an important part, though the father digs the grave. Only the parents perform the sexual rites of purification: other villagers need not. If the child has been initiated its spirit is consigned to the ancestors. Old people are already so closely associated with death that they are sad to "go home" and their burial rites are few. A woman's death, unless she is the chief wife of a headman, affects only her own family. Strangers and friendless people, having no social relationship with the community, are buried without ceremony. In the descriptions of chiefs' funerals one finds that little attention is paid to their relations with their families. Apparently a chief's importance as head of is tribe overrides family relationships. Great care is taken to maintain peace in the country; otherwise noteworthy are the comparative magnificence of the funeral and the attendance of large numbers of tribesmen.

Warriors killed in battle and people killed by violence are not buried in the village lest they bring death with them. Lightning especially is a dread contaminating force, and the villagers must be cleansed by a special magician. The village is abandoned. There is no mourning lest Heaven which sent the lightning be offended. Certain criminals, such as wizards, have their bodies thrust out into the bush.

But the readjustment of social relationships does not explain the whole reaction to death. Most primitive funeral rites show no patient resignation to the death, but a determined opposition to it, expressed among the South-Eastern Bantu largely by the idea that it must be due to a mystical cause (sorcery or witchcraft). But here the strongest notion is that of the contaminating effect of the death which extends to relatives, material objects and food. Medicinal washings and protective rites, directed by a magician, and appeals to the ancestors and the dead man, are used against this contamination, as well as taboos to be observed for a period. These mourning taboos and reactions are a mode of expressing kinship relationships and are referred to as evidence in legal disputes. Some of the dead person's most personal effects are so closely related to him that they must be destroyed or buried with him. In communities where most deaths are ascribed to mystical cause the idea seems to be that now these forces have a footing in the group steps must be taken to expel them or to protect the survivors. To the Maulu of New Guinea the spirit is always evil and it must be driven away, and perhaps with it the cause of death. The South-Eastern Bantu hope the spirit will be beneficent (thus they appeal to it) and they have to keep it in the ancestral cult; therefore they protect themselves ritually against death, as can be seen in the custom of burying those who die by violence facing away from home, and they may in addition attack the cause of death by punishing the wizard who caused it. This last reaction is not, as among the Venda 12 and Azande, 13 essential: there is no mandate enjoining vengeance, and one cannot tell from the records how often it is done. Mrs. Kuper tells me that according to the Swazi the ancestral spirits may make a man very ill, but they never kill him.

III
There are, it seems to me, two aspects of survival after death: the journey of the spirit to and its continued existence in another sphere of living, and the relations of the dead with the living. Most people pay attention to both of these aspects. But it also seems that social attention when directed to the second emphatically in the form of an ancestral cult tends to exclude any emphasis on the first. If an ancestral cult may be defined as the belief in the continued inference of ancestral ghosts in the affairs of their living kin and continual ritual behaviour by the latter to the former, 14 I think it will be found in general that people with a well developed cult of tendence on the ghosts have a very inchoate picture of the afterlife, which will depend on individual imagination rather than cultural dogma. A number of problems are suggested by this: firstly, how is it possible to measure the intensity of ritual beliefs and behaviour for purposes of comparative study. Secondly, how frequently does the dead's paramount importance as related to their descendants exclude cultural attention from the afterlife, and how does this affect mourning customs and the disposal of corpses. Thirdly, why do particular societies have an ancestral cult: why, if it is a matter of extended kinship grouping do some societies with that form of grouping not have the cult, and how is the belief in active interference by the ancestors related to the social existence of gods and other spirits.

The first problem must be settled if social anthropology is to progress in the comparative study of ritual. Thus where an ancestral cult is concerned one would require to know how often and in what situations the people thought of and approached their ancestors, and as far as possible how they evaluated the cult in relation to other modes of behaviour, i.e. what satisfaction it gives them. Then the same questions would have to be answered about magic and the belief in gods. In view of my inability to judge these cults from existing data I can do little more than suggest some lines on which enquiry may be made.

How far does the concentrating of cultural attention on the relations of dead ancestors with their living descendants exclude attention from the afterlife? In some societies neither system is at all developed, but reference to others 15 shows that where one is important the other is always inchoate. The two are not found together. Thus Fijians, North American Indians, Egyptians, Romans, Greeks, have an elaborate mythology of the journey to the afterworld and what happens to the ghost there, unlike African tribes which, with their ancestral cult, have left the picturing of the afterlife to the individual - and it is a life more or less like that on earth. 16 The importance of the distinction is, firstly, that it may indicate a general tendency for cultural attention to concentrate on one only of several aspects of a phenomenon, at any rate in some particular situation. The other aspects will only be consciously evoked when some special situation occurs. Secondly it may be correlated with ritual practice. Thus in certain societies where there is no ancestral cult a large part of the mourning ceremonies are concentrated on the dead person and on helping his spirit on the perilous journey to the afterworld. 17 Among these societies the individual's desire to survive death might be of importance and it must be noted that Malinowski studied a society of this type. But the ancestor-worshipping Bantu are only concerned with instituting the dead man safely as an ancestral spirit and they have no mythology of his passage from this life and no developed notion about the soul. The body is carefully disposed of and the chief importance of the grave is that the spirit will be approached at it. Thus headmen of families who become the spirits really approached are buried in the cattle-kraal, the temple of the village, 18 or among the Thonga in the sacred groves. The graves of chiefs remain marked as sacred places, even sanctuaries. The Zulu and Thonga chiefs' hair and nail parings are preserved in sacred tribal symbols and often some attempt is made to mummify the bodies of chiefs. Their graves are more solid and the location of their graves is sought to be preserved by groves of trees and legends, so that the people can often return miles to sacrifice there. In addition their greater social importance is thus expressed. When a village is moved ritual is performed to transport the ancestors to the new site. Generally the form of the grave 19 (among the South-Eastern Bantu it is supposed to represent a hut with a square outside) seems to reflect the idea that after death the individual is not greatly changed. The graves of chiefs are always sacred; other graves only in the situation of sacrifice, otherwise probably only scant attention is paid to them, or to such places as the back of the great hut of the village where the ancestors dwell. Dr. Fortes has remarked that this is so of shrines among the Gold Coast Tallensi, a conclusion borne out by Dr. Evans-Pritchard's observations in the Sudan. The grave and the existence of the spirit are unimportant except when evoked in the ancestral cult: the main purpose of the burial rites is to restore kinship relationships among the survivors and of the dead man to his ancestors and descendants.

The South-Eastern Bantu have a hierarchical society of ancestors manifesting active interest according to their status when alive in their descendants. 20 Mrs. Hoernlé points out that in all the South African tribes one of the strongest bonds holding individuals together is descent from a common ancestor. Their social organisation is built up largely on the basis of kinship for members of the same lineage tend to live in the same village or at least close to one another in the same area. The closest bond naturally is between members of the same family, i.e. between siblings and their descendants; the links between these people are not broken as the years go by, though since kinship is patrilineal and marriage patrilocal it is inevitable that a number of brothers can more easily maintain contact with each other than with their sisters who move off in different directions as they marry. Moreover inheritance is from father to sons or from brother to brother and then to the eldest brother's sons, and therefore a closer link is established in this line. Now many peoples have a kinship organisation of this type, and some of these are linked, in their smaller groupings, by a definite association with a specific area of land and through the possession of hero-gods, totems or badges. This does not apply to any of the smaller social groupings among the South-Eastern Bantu, though the tribe is intimately bound to its land. Therefore among the South-Eastern Bantu the links between living people are maintained by keeping in mind their actual common descent. Bryant says of the Zulu that "the preservation of pedigrees with them was absolutely necessary, because without it mutual relationships, with their appropriate terms of address, would never have been known." 21

This is obvious and easy for the individual family and even for the group descended from a common grandfather but as the ramifications of kinship become more complicated and the group larger "it needs a distinct effort and organisation of a high type to keep the links strong. It is obvious that the common ancestor must be remembered, and it is much easier to remember if there is a definite cult of remembrance, a definite ritual which brings those together who are of common kin so that they are perpetually reminded of their bonds." 22 This is done by sacrifices and commemoration, and it must be remembered that tendence on the ancestors is compulsory. A man may or may not believe in magic, but if the ancestors send him illness he must sacrifice, and there are certain periodic obligations to them which must be fulfilled, at birth, initiation, wedding, and death ceremonies. For a breach of custom they can punish and here their power is the same as that of Bantu elders to curse erring relatives. 23 Since, moreover, it is only these elders who have the right to sacrifice, their social position is strongly entrenched. A junior who has quarrelled with his senior must in the end, when he is in trouble, make amends. All the family should attend, and Blohm remarks that among the Xhosa even Christian converts had perforce to attend sacrifices lest they be expelled from their families. 24

Once the people linked by a common ancestor separate; they forget that ancestor as they lose their ties of communal life, and if they forget that ancestor they tend to drift apart 25 and perhaps to sacrifice to and approach a new founder. "A group therefore will be larger and stronger the longer the line of ancestors it can count, the further it can grope back into the past for its beginnings. Since the people are linked together through their ancestors the dead must not be lost to society. They represent the past life of the group, links binding together the living. The cult of the ancestors then gives life to the kindred which it would not otherwise possess." This may be seen in the manner in which the ancestors and their great deeds are praised at marriages, births, feasts, and funerals. For the dead are held on to and thought merely to be initiated into another part of society, the spiritual and unseen but potent part of it, and the people are perpetually concerned with maintaining contact with this unseen world.

Mrs. Hoernlé thus suggests possible answers to some of the questions I have posed. She points out that the ancestral cult is associated with a system of extended kinship where the kin are organised into a strong social group which tends to split up as it increases. The ancestral cult is a mechanism by which kinship bonds are affirmed (among the Thonga matrilineal as well as patrilineal bonds) and the hierarchy of society expressed. In this the ancestral cult is, like much ritual, a form of mnemonic, legally prescribed actions which vividly express social relationships.
I have spoken above of the patrilineal lineage among the South-Eastern Bantu as a strong social group. My recent researches in Zululand indicate that the Natives themselves do not think of this group, or of a clan, but think in terms of people with the same isibongo (clan-name). That is, we abstract the group. Mrs. Kuper confirms this of the Swazi. The Zulu have no word to describe a clan, as they have for political areas. But the Xhosa and Mpondo have such a word. However, my point here is that the ancestral cult is a mnemonic of kinship relationships, and since among the Thonga the matrilineal kin are important one finds among them that matrilineal ancestors are important.

In many societies there is a cult of the dead which is not a cult of the ancestors, since no tendence is paid to a line of ascendants. In others the spirits of the dead, especially of rulers, are important, but not the spirits of dead kinsmen as such. In modern spiritualism we are afforded a chance to examine the growth of a ghostcult and see whether it is affected by social groupings. As far as I can judge from spiritualist conversations 26 these deal mainly with the fate of those at the seance (the living of course) or the contact of the spirits with the earth, and very little, despite the theory of seven dimensions, with the life of the spirits themselves. And then, it seems to me, it is only by forcing a polite interest that people ask questions about that life, to get the same answer as the Bantu tribesman gives - a world better than, but more or less like, our own. Here however dogma is not yet clearly formulated. The springs of genuine spiritualism are mainly the desire to get into touch with dead relatives, but one cannot do so directly. One must do it through one's own, and the medium's, spirit guides. Of them we each have two or three. At the seances I attended there were two mediums: the first, a Christian woman, was "guided" by three spirits, those of an American missionary, a Hindu, and a Turkish girl who died at the age of two; the second medium, a naturalised South African Jew, had as his guides an American Negro vaudeville singer and a Lithuanian cantor - of a New York synagogue. The guides mentioned by Bradley are equally exotic. The "mediums" of the Thonga and other primitive tribes are also "possessed" by foreign spirits; but the ordinary tribesmen (and Zulu mediums) receive guidance from their dead kin. In spiritualism we are all accompanied by foreigners who will call up our relatives, i.e. where the important social kinship group is the family, the attendant spirits are not kinsmen: and similarly in the Andamans 27 a man sees-not his own dead ancestors, but just ghosts in the forest. It may be that in the growth of spiritualism one can see how social morphology may determine dogma, in that people are guided by stranger-ghosts, unlike the Bantu tribesmen whose kindred-ghosts advise them with dreams and omens, though their wishes may have to be interpreted by a skilled "medium" who acts with certain techniques and occasionally with stranger-ghosts. In an appendix on the ancestor cult Junod makes a similar point in comparing the Thonga and Ila with the Akamba, among whom the largest kinship unit is the family, and the power of the ancestors is "reduced to a minimum; though they are very much feared they are thought to be mortal." 28

Mrs. Hoernlé suggests another line of enquiry when she says that many peoples who have a kinship organisation similar in type to that of the South-Eastern Bantu, but no ancestral cult, maintain their association by reference to a specific area of land, or by possession of hero-gods, totems or badges. The point is that in all these cases ritual is a means of expressing the structure of the group; and a tendency to do this runs through all South-Eastern Bantu ritual. It may be noted that the South-Eastern Bantu lineage relates to a specific area of land only in so far as its ancestors are buried there 29 and when migrating it takes ritual steps to carry its ancestors with it. 30 In many communities the kinship group seems to maintain itself by owing a particular area of land. Thus for example there are Scottish clan demesnes (and names), the Iroquois long houses 31, Algonkian hunting areas, 32 and Hottentot waterholes. 33 Radcliffe-Brown has stressed that one of the main features of totemism is its relation to this type of social grouping, 34 generally with no ancestral cult. The several kinds of ritual mechanism for maintaining cohesion exist side by side in some communities; but one or other tends to be dominant.

But once this rough correlation is established it is not yet clear why any society should have one ritual rather than the other. An explanation of this can probably be offered only in historical terms. However, if other culture traits which accompany each of these rituals be investigated, it seems that the clan association with land is found with one or two sets of environmental factors. Firstly it is found as among the Hottentots where land is plentiful but water limited, and ownership of waterholes is important; and this is also what constitutes the clan bond in Australian tribes where totemism is associated with local totemic spots and reincarnation, rather than with descent groups. Secondly Scottish clans and old English families are associated with land in a country where it is all taken up. The real totemic cult (an active ritual, not mere prohibitions) is found in hunting communities and it may be noted that hunters such as the Andamanese, Bushmen and Algonkian who have no such cult, have no clan grouping. With all these societies one may contrast the South-Eastern Bantu, pastoral-agriculturalists with spacious land and organised in lineages.

I have now to consider the relation of the ancestral cult to other ritual practices. As far as South-Eastern Bantu magic is concerned it is related in that the two practices are used together, and in many instances the power of medicines is increased by the ancestors, from whom knowledge of the medicines was probably obtained. This is particularly noticeable of socially important magic. Other magic may be bought, sold and taught outside the kinship group, but in general in their magic the substance used is of greatest importance: the spell is included in a prayer to the ancestors which gives the magic its social character and which guarantees the right and power of the magician to use it.

There are other spirits and spiritual beings besides ancestral ghosts. Among the South-Eastern Bantu they are of two kinds, what one may call for want of better terms "demons" and "gods". The demons are evil spirits: souls not properly buried (a sanction enforcing observance of mortuary customs); the spirits of living and dead which have fallen prey to wizards; and certain sprites which exist in their own right but may be used by wizards. These demons are held responsible for ill which is not attributed directly to wizards, or to the vengeance of the ancestors among whom female spirits are capriciously evil. In other words these evil spirits and sprites are used to explain certain misfortunes. What misfortunes I cannot on the data available detail, though they are sometimes suspected of causing certain illnesses. But here in the South-Eastern Bantu ritual system the action of wizards, demons and ghosts are interwoven in complicated ways and to which of them attention will be directed by the diviner in any situation it is, on the evidence available, impossible to say.

The South-Eastern Bantu have very incomplete conceptions of "gods". They may be said to have two of these gods, Heaven (representing storms and certain other dread phenomena) and a "First Man" who initiated the life of men. The Zulu have in addition a certain goddess, Nomkubulwana, who figures in hoeculture 35. The First Man (Zulu Unkulunkulu) does not figure at all in ritual practice; he is one of Seligman's "otiose High Gods"; he is merely a final reference in mythology to explain such facts as creation and death. Heaven appears in ritual chiefly as a vast destructive power, more or less personified, in situations of tribal catastrophe such as drought, floods, locust invasions, blight, and among the Thonga in the birth of twins. In ordinary life Heaven is referred to when a man is killed by lightning, suddenly and inexplicably. Thus Heaven is evoked in South-Eastern Bantu consciousness rarely and in overwhelming situations. 36 Usually attention is directed to ancestors and wizards. And to deal with Heaven there are therefore special ritual techniques conducted by magical specialists of high standing.

Viewing the problem comparatively one notices that the ancestral cult is seldom found with a deistic ritual. In Hebrew history the religion of Jahweh had continually to struggle with the tendency to approach the dead. 37 Generally the idea of "High God(s)" seems to be found in simple undifferentiated communities such as the Bushmen, Hottentots, Andamanese and Australians, and in communities with a highly developed centralised organisation, such as the Egyptians, Romans and certain Bantu. 38 In fact in these latter communities the development of the political organisation seems to be accompanied, where there is not already belief in a High God, by the growth of the god. Where the belief exists the head of the state becomes defender or representative of the god. In South-Eastern Bantu ritual the ancestors of the chief are almost gods already; in Hebrew history the development of the state sees the growth of Jahweh; in Roman history the emperor becomes deified. In such communities one tends to find the divine king, as Seligman recorded of the Shilluk. Throughout Africa the political development of the tribe shows this tendency to deify the chief's ancestors and ultimately the chief himself, as might have happened to Shaka if he had not been assassinated. Certainly one may observe it of the Ashanti, Baganda and Rozwi chiefs. 39

To sum up the comparisons as applied to the South-Eastern Bantu, one finds that social morphology affects death customs and the belief in immortality in that under their mode of life and social organisation they have an ancestral cult which is a means of maintaining kinship groupings; it is accompanied by inchoate ideas about the existence of the soul in the living and after death, and the future existence of the ghost is reflected in mortuary customs. The ancestors of the chief are tending to become gods; other gods are on the whole unimportant.
In South-Eastern Bantu society then the ancestral cult is the chief aspect of immorality (in the sense of continued existence for a time after death, not eternal imperishability), and it is related to the lineage; it has little social importance for individuals as compensation for death. Emotional value in that way it may have. However when Manyibane the Thonga lay dying his care was not for his soul but to settle his affairs on earth. Yet death is not conceived to be on the natural order. In no society is that admitted. Death myths express both the desire for life and the recognition of death as a fact. Death is unnatural as the mythical causes of it show for it is introduced to man as the result of negligence or evil, and usually the cause is very minute, e.g. a chameleon's pausing to eat berries, the eating of an apple, a bird's singing. It is always an upsetting of previously existing conditions in which dying had no meaning for man. 40

BIBLIOGRAPHY
(I am grateful to Mrs. Hoernlé and Father Bryant for allowing me the use of their manuscripts.)
Blohm, W. "Das Opfer und Dessen Sinn bei den Xosa in Südafrika," Archiv für Anthropologie, N.F. 23, p. 150.
Bradley, Dennis. "Towards the Stars" and "Wisdom of the Gods."
Bryant, A.T.
(a) Manuscript: 'The Zulu as they were before the White Man Came."
(b) Olden Times in Zululand and Natal, 1929.
(c) "The Zulu Cult of the Dead." Man (1917), No. 95.
Callaway, The Rev. Canon. Religious Systems of the Amazulu, 1868.
Cook, P.A.W. Social Organisation and Ceremonial Institutions of the Bomvana.
Evans-Pritchard, E.E.
(a) "Some Collective Expressions of Obscenity in Africa," Journal of the Royal Anthropological Institute, Vol. LIX, p. 323.
(b) Witchcraft Magic and Oracles among the Azande, 1937.
(c) "Zande Theology," Sudan Notes and Records, 1936.
Gluckmann, Max. "Zulu Women in Hoeculture Ritual," Bantu Studies, September, 1935.
Goldenweiser, A.A. Early Civilisation.
Hastings Encylopoedia of Religion and Ethics
(a) "Ancestor-worship and the Cult of the Dead," Vol. 1.
(b) "Death and the Disposal of the Dead," Vol. 4.
Hoernlé, A.W.
(a) Manuscript - "The Relations between the Living and the Dead among the Bantu of South Africa" (1933).
(b) "Religion in Native Life" in Thinking with Africa, ed. by W. Stauffer, 1928.
Hunter, M. Reaction to Conquest, 1936.
Jaques, A.A. "Terms of Kinship and Corresponding Patterns of Behaviour among the Thonga," Bantu Studies, Vol. III, No. 4.
Junod, H.A. The Life of a South African Tribe, (2 volumes), 2nd Edition.
Malinowski, B.
(a) "Magic, Science and Religion," pp. 79-84 in Science, Religion and Reality (1925) ed. by J. Needham.
(b) Essay in Science and Religion, 1930.
Radcliffe-Brown, A.R.
(a) The Andaman Islanders, 2nd edition, 1930.
(b) "The Methods of Ethnology and Social Anthropology," South African Journal of Science, 1923, p. 124.
Robertson, Howard. Architecture Explained.
Schapera, I.
(a) The Bantu-Speaking Tribes of South Africa, ed. by Schapera, 1937.
(b) "Oral Sorcery of the Natives of Bechuanaland" in "Essays Presented to C.G. Seligman," 1934.
(c) The Khoisan Peoples of South Africa, 1930.
Soga, J.H. The AmaXosa: Life and Customs, 1931.
Speck. "The Family Hunting Band as the Basis of Algonkian Social Organisation," American Anthropologist, Vol. 17, pp. 289 seq.
Stayt, H.A. The Bavenda, 1931.
Wallis, W.D. "Similarities in Culture," American Anthropologist, Vol. 19.
Wangemann. Die Berliner Mission in Zululand.
Wedgwood, C. "Death and Social Status in Melanesia," J.R.A.I., Vol. LVII.

Introduction to Reasearch Methods and Program Evaluation by Dr. David Abrahams

Introduction to Reasearch Methods and Program Evaluation by Dr. David Abrahams

Introduction to Research
"If we could first know where we are, and wither we are trending, we could better judge what to do and how to do it." Abraham Lincoln

Misuse or Misspoken use of Research
Frequently you find published research results in newspapers, magazines and on the television that fail to explain how they came to gather or analyze the results they are reporting. Related to this, are issues of results being misused, embellished or taken out of context. For example, during an election time, more and more news and television organizations conduct quick polls and surveys. They report and discuss the findings as valid unbiased indicators about a candidate’s position or the public views on an issue. Not once during their broadcast or while you are reading the article do they speak about how the data was gathered or what analysis were performed to get the results they are reporting. All of these individuals and groups claim to have conducted some form of research but fail to validate their findings.

It is important to qualify the point I am making; I am not saying that these activities are not important or lack value to the gatherers of the information. However, these activities lack rigor and do not meet the definition or the criterion of research. At best this type of research is informative, an indicator to an assumption, or a mechanism that alerts you to group and social trends, issues, and impressions.

It is important to make the distinction because of the value people attach when reading or are told that the findings are a result of research. The implication is that these results or finding are reliable and valid. RELIABITY is an indication of how sound your research is and applies to both the design and the methods of your research; it is a measure of whether the results are replicable. VALIDITY refers to the degree to which a study accurately reflects or assesses the specific concept that the researcher is attempting to measure. Validity is a measure of accuracy and whether the instruments of measurement actually are measuring what they are intended to measure. Research can be affected by any internal or external factors, which can impact the reliability and validity of that research. Controlling all possible factors that threaten the reliability and validity of the research is a primary responsibility of every good researcher.

The function of research is to either create or test a hypothesis. Research is the instrument used to test whether a hypothesis is good or not. It is the method by which you identify a problem, form a hypothesis, design an experiment, test the hypothesis, analyze the results, formulation and report conclusions. There are different ways of conducting research; however any method you use will be based on the systematic collection and analysis of data. The emphasis here is on the word systematic.

Research can be broadly defined as a form of systematic inquiry that contributes to knowledge. It is also important to understand what is meant by this term research. Research is about finding out. It is about searching systematically for solutions to problems. It is about a structured process and rules that guides you to the results. It is also about helping you to evaluate the research of others.

What is Research?
“Research is formalized curiosity. It is poking and prying with a purpose.” Zora Neale Hurston

Research is the cornerstone of any science, including both the hard sciences such as chemistry and physics and the social (or soft) sciences such as psychology, management, or education. It refers to the organized, structured, and purposeful investigation aimed at discovering, interpreting, and revising human knowledge on different aspects of the world by someone first hand. The setting may vary from natural, real world too highly constrained and carefully controlled laboratory environment.

Many argue that the structured attempt at gaining knowledge dates back to Aristotle and his identification of deductive reasoning. Deductive reasoning refers to a structured approach utilizing an accepted premise, a statement that is assumed to be true and from which a conclusion can be drawn.

Deductive reasoning utilizes, a major premise (a universal affirmative or negative proposition that is assumed to be true) and a minor premise (a particular affirmative or negative proposition that is assumed to be true), and a conclusion. This method of gaining knowledge, going from the general to the specific and drawing a conclusion, can also called a syllogism. For example:

All apples are fruit.
All fruits grow on trees.
Therefore all apples grow on trees.
Or
All apples are fruit.
Some apples are red.
Therefore some fruit is red.

Intuitively, one might deny the major premise and hence its conclusion; yet anyone accepting the premise accents’ the conclusion. Deductive reasoning is dependent on its premises and research is dependent on its hypothesis. Both have a similar weakness, that is, a false premise/hypothesis can possibly lead to a false result, and inconclusive premises/hypothesis will also yield an inconclusive conclusion. Example, the premise:

Dolphins are mammals, not fish.
Dolphins swim in the ocean.
Therefore, fish do not swim in the ocean.

In this case, the premise that "dolphins are mammals, not fish" is undistributed, but ends up (improperly) as part of the conclusion. The part of the conclusion that's wrong is the predicate "do not swim in the ocean. As a result, we cannot properly conclude that all fish do not swim in the ocean. Or, the hypothesis:

A survey indicates that the bird population in a certain area is declining. There is a statistical correlation with the increase in the human population and the decline of that bird population. Therefore, the decline in the bird population is due to the increase in the human population.

There may be a correlation, but without looking at other factors including disease, parasites, climate change and chemical threats, a valid case cannot be made that the decline in the bird population is due to increases in the human population.

Statistics is used to examine or study everything of interest (such as an item, person, how a person plays baseball, is something safe, how well a business is doing, or how much an endangered animals population has declined or grown in the past five years and if that change is significant). For example, suppose we are interested in who is winning the Democratic Primary Elections? We cannot ask every single person who voted or what their opinion is!

However, we can ask a selection of people. This raises a number of questions, however:
• What group of people do we choose?
• Who should be in the group?
• What can information gathered from a small group of people tell us about the voting outcome in the population in general?
• Won't the measured effect or outcome depend on which people are in the group? Won't it change from one group to the next? So, how can any useful information are found?
• How many people should be in such a group to obtain useful information?
To answer these questions, we need statistics and we need to know how to Research.

Introduction to Research Design "It is the theory that decides what can be observed." Albert Einstein

Experiments, if conducted correctly can enable a better understanding of the relationship between a causal hypothesis and a particular phenomenon of theoretical or practical interest. One of the biggest challenges is deciding which research methodology to use. “Research that tests the adequacy of research methods does not prove which technique is better; it simply provides evidence relating to the potential strengths and limitations of each approach.” (Howard, 1985).

In research and evaluation, a true experimental design (also known as random experimental design), is the preferred method of research. It provides the highest degree of control over an experiment, enabling the researcher the ability to draw causal inferences with a high degree of confidence.

A true experimental design is a design in which subjects are randomly assigned to program and control groups. With this technique, every member of the target population has an equal chance of being selected for the sample. The fact that every member of the target population has an equal chance of being selected for the sample makes this design the strongest method for establishing equivalence between a program and control group.

Quasi-experimental group design differs from true experimental group design by the omission of random assignment of subjects to a program and control group. As a result, you can not be sure that the program and the control group are equivalent.

The use of random experimental design to randomly assign subjects to a program and control group, controls for all threats to internal validity. Issues of internal validity arise when groups in the study are nonequivalent. Your ability as a researcher to say that your treatment caused the effect is compromised.

In most causal hypothesis tests, the central inferential question is whether any observed outcome differences between groups are attributable to the program or instead to some other factor. In order to argue for the internal validity of an inference the analyst must attempt to demonstrate that the program and not some plausible alternative explanation is responsible for the effect. In the literature on internal validity, these plausible alternative explanations or factors are often termed threats" to internal validity" (Trochim, 1997).

Let us consider an instance in which an investigator wishes to determine if a program designed to reduce prejudice is effective. In this instance, the independent variable is a lecture on prejudice for grammar school students. For the dependent measure, the researcher will use a standard self-report test of prejudice. To conduct the study, the researcher selects a group of students from a local grammar school and administers the prejudice questionnaire to all of them. A week later, all the students receive the lecture on prejudice and, after the lecture, again are tested. The next step is to find out whether the prejudice scores collected before the intervention (call them the pretest scores) are substantially higher than scores obtained following the lecture (the posttest scores). The researcher might conclude that, if the posttest responses are lower than the pretest responses, the intervention has reduced subjects' prejudice. As you can see, what the researcher has done is assume that changes in the dependent variable were caused by the introduction of the independent variable. But what possibilities other than the operation of the independent variable on the dependent variable might explain the observed relationship (Campbell & Stanley, 1963)? The section on experimental design explains several such threats to internal validity .

This is an important point to note. The research designs and methods used in an evaluation have a direct effect on whether or not a program is perceived effective. Did the cause really produced the effect or was it some other plausible explanation? If the cause produced the effect, can it be generalized to a different group in another location? These are questions of validity. "The first thing we have to ask is: "validity of what?" When we think about validity in research, most of us think about research components. We might say that a measure is a valid one, or that a valid sample was drawn, or that the design had strong validity. All of those statements are technically incorrect. Measures, samples and designs don't 'have' validity -- only propositions can be said to be valid. Technically, we should say that a measure leads to valid conclusions or that a sample enables valid inferences, and so on. It is a proposition, inference or conclusion that can 'have' validity" (Trochim, 1997).


Validity
“We are to admit no more causes of natural things than such as are both true and sufficient to explain their appearances.” Isaac Newton

Internal Validity and its Most Significant Threats
Threats to validity can be either internal, external, or both. A threat to validity, by definition is, any factor that influences the results of the experiment. In research and evaluation, internal validity refers to the degree the treatment or intervention effects change in the dependent variable. The greater the ability a researcher can attribute the effect to the cause, rather than to extraneous factors the higher the degree of confidence that the treatment or intervention caused the effect.

Internal validity is only relevant in studies that try to establish a causal relationship. It's not relevant in most observational or descriptive studies (Trochim, 2006). Controlling for potentially confounding variables minimizes the potential for an alternative explanation of the treatment effects. The most significant threats to internal validity are: history, maturation, testing, instrumentation, regression, selection and experimental mortality.

History
History becomes a threat when other factors external to the subjects (in addition to the treatment variable) occur by virtue of the passage of time. For example, the reported effect of a year-long, institution-specific program to improve medical resident prescribing and order-writing practices may have been confounded by a self-directed continuing-education series on medication errors provided to residents by a pharmaceutical firm's medical education liaison.

Maturation
The maturation threat can operate when biological or psychological changes occur within subjects and these changes may account in part or in total for effects discerned in the study. For example, a reported decrease in emergency room visits in a long-term study of pediatric patients with asthma may be due to outgrowing childhood asthma rather than to any treatment regimen imposed. Both history and maturation are more of a concern in children and longitudinal studies.

Testing
The testing threat may occur when changes in test scores occur not because of the intervention but rather because of repeated testing. This is of particular concern when researchers administer identical pretests and posttests. Researchers that have subjects performing skilled based task, test of memory, IQ or Manual dexterity must take the threat of testing into account when designing their research at posttest. For example, a reported improvement in medical resident prescribing behaviors and order-writing practices in the study previously described may have been due to repeated administration of the same short quiz. That is, the residents simply learned to provide the right answers rather than truly achieving improved prescribing habits.

Instrumentation
When study results are due to changes in instrument calibration or observer changes rather than to a true treatment effect, the instrumentation threat is in operation. Instrumentation is a threat when study results are due to changes in the instrument calibration or observer changes rather than to a true treatment effect; this is especially true when the measuring instruments are human observers. For example: a human observer might become more proficient as a observer, noticing patterns and nuances in an observed subject that might have existed in the pretest but are only noticing it in the posttest. As a result the observer incorrectly attributes the observed change to the treatment.

Regression
Statistical regression threat is a threat to internal validity when subjects are assigned to treatments on the basis of extreme (low and high) scores on a test. During retest, the scores of extreme scorers tend to regress toward the mean even without treatment. For example, if a group of subjects was recruited on the basis of extremely high or low scores and an educational intervention is conducted, any post intervention improvements could be due partly or entirely, to regression rather than to the educational treatments presented in the program. Conceptually, the initial extremely high test score was attributed to measurement error (represented in the variability of test scores). When this changed randomly during the next test, high scores were no longer as high as before. The result is a regression towards the mean.

Selection
The selection threat is of utmost concern when subjects cannot be randomly assigned to treatment groups, particularly if groups are unequal in relevant variables before treatment intervention. For example, one obstetrics and gynecology clinic's patients receive a pharmacy-based educational intervention and another clinic's patients receive a mailed pamphlet; both methods are designed to encourage calcium supplementation. When the outcome is measured at the end of the study, it may be confounded by the fact that the groups were not equal with respect to relevant variables (e.g., age, race, income status, hysterectomy status, and menopausal status) before the educational program was implemented.

Experimental Mortality
Experimental mortality is also known as attrition is when subjects drop out of an experiment/treatment before the study is completed. Experimental mortality is a treat to internal validity when there is a differential loss of subjects from comparison groups resulting in unequal groups (Campbell and Stanley, 1963: 5). One example is a study designed to compare the effectiveness of a drug on a randomly selected group of sick participants. One group receives the drug/treatment and the other group receives the placebo. If subjects with the most severe symptoms dropped out of the active treatment group, the treatment may appear more effective than it really is.

External Validity
External validity is the degree to which the results of the study can be generalized to a population other than those studied. External validity is widely treated as an issue to be addressed through methodological procedures. In a study, it is usually impossible to measure an entire population; as a result, measurements are taken from a sample of that population. If subjects from a sample population are not randomly selected from the population, then their particular demographic, for example there: household, age, socio-economic, ethnic, racial, religious and/or income characteristics may bias their performance and the study's results may not be applicable to the population or to another comparable group.
The purpose of research is to learn something about the behavior of people. This knowledge is useful only to the extent that we can generalize the information to a larger population. However, the more we control the environment of the subjects (sub population) in a study, the more the subjects in the experimental and control groups can become different from those in the general population. Consequently, the results may have high internal validity; they may also lack external validity, meaning that they cannot be generalized beyond the particular groups used in the experiment.
Random assignment of treatment and control groups address the threats to internal validity and often create threats to external validity. When designing an experiment, each experimenter has to decide which requirement is more important, internal or external validity, and seek a balance between the two. The designed and execution of the experiment is the most effective way of testing for the effects of one variable on another variable.
Threats to External Validity
Del Siegle, Ph.D.Neag School of Education - University of Connecticut. Web: http://www.gifted.uconn.edu/siegle/research/Samples/externalvalidity.html

Population Validity is defined as the extent to which the results of a study can be generalized from the specific sample that was studied to a larger group of subjects. They are:
The extent to which one can generalize from the study sample to a defined population. Therefore, if the sample is drawn from an accessible population, rather than the target population, generalizing the research results from the accessible population to the target population is risky.
The extent to which person logical variables interact with treatment effects. Thus, if the study is an experiment, it may be possible that different results might be found with students at different grades (a person logical variable).

Ecological Validity is defined as the extent to which the results of an experiment can be generalized from the set of environmental conditions created by the researcher to other environmental conditions (settings and conditions). They are:

Explicit description of the experimental treatment (not sufficiently described for others to replicate). If the researcher fails to adequately describe how he or she conducted a study, it is difficult to determine whether the results are applicable to other settings.
Multiple-treatment interference (catalyst effect); if a researcher were to apply several treatments, it is difficult to determine how well each of the treatments would work individually. It might be that only the combination of the treatments is effective.

Hawthorne effect (attention causes differences); subjects perform differently because they know they are being studied. "...External validity of the experiment is jeopardized because the findings might not generalize to a situation in which researchers or others who were involved in the research are not present" (Gall, Borg, & Gall, 1996, p. 475)

Novelty and disruption effect (anything different makes a difference); A treatment may work because it is novel and the subjects respond to the uniqueness, rather than the actual treatment. The opposite may also occur, the treatment may not work because it is unique, but given time for the subjects to adjust to it, it might have worked.

Experimenter effect (it only works with this experimenter); the treatment might have worked because of the person implementing it. Given a different person, the treatment might not work at all.

Pretest sensitization (pretest sets the stage); A treatment might only work if a pretest is given. Because they have taken a pretest, the subjects may be more sensitive to the treatment. Had they not taken a pretest, the treatment would not have worked.
Posttest sensitization (posttest helps treatment "fall into place"); the posttest can become a learning experience. "For example, the posttest might cause certain ideas presented during the treatment to 'fall into place' " (p. 477). If the subjects had not taken a posttest, the treatment would not have worked.

Interaction of history and treatment effect (...to everything there is a time...); not only should researchers be cautious about generalizing to other population, caution should be taken to generalize to a different time period. As time passes, the conditions under which treatments work change.

Measurement of the dependent variable (maybe only works with M/C tests); A treatment may only be evident with certain types of measurements. A teaching method may produce superior results when its effectiveness is tested with an essay test, but show no differences when the effectiveness is measured with a multiple choice test.
Interaction of time of measurement and treatment effect (it takes a while for the treatment to kick in); it may be that the treatment effect does not occur until several weeks after the end of the treatment. In this situation, a posttest at the end of the treatment would show no impact, but a posttest a month later might show an impact.

Bracht, G. H., & Glass, G. V. (1968). The external validity of experiments. American Education Research Journal, 5, 437-474.
Gall, M. D., Borg, W. R., & Gall, J. P. (1996). Educational research: An introduction. White Plains, NY: Longman.

Random Assignment
Newton, Isaac (1642-1727) ...from the same principles, I now demonstrate the frame of the System of the World.
What is necessary for an assignment to be considered random? The most important requirement is that each participant or subject in the study have an equal chance to be assigned to a group. Statistically, “equal chance” is expressed as “.5” or “50%.” One method is to randomly assign the subjects to two groups by flipping a coin. If the result of the coin toss is heads, the subject is assigned to one group. If the result is tails, the subject is assigned to the other group. A more effective method for random assignment is to use a personal computer with a statistical program like Mini-Tab or SPSS to randomly assign the subjects to groups.
Random Sampling is not a complete representation of the population from which it was drawn, this random variation in the results is known as sampling error. Sampling error or estimation error is the error caused by observing a sample instead of the whole population. Mathematical theory is available to assess the sampling error. Estimates obtained from random samples are accompanied by measures of the uncertainty associated with the estimate. This can take the form of a standard error, or if the sample is large enough for the central limit theorem to take effect, confidence intervals may be calculated.
The following link is an exercise desisigned to teach about random sampling and assignment. Random Assignment Tutorial. If you would like to generarate your own random numbers for your project Research Randomizer has a Randomizer form to instantly generate random numbers. Randomizer form

Design Notation
"The greatest challenge to any thinker is stating the problem in a way that will allow a solution." Bertrand Russell

Design notation is a way to indicate the number of factors and the number of levels of each factor. This system provides the researcher with all the information necessary for describing an experimental design. Be aware of the fact that design notation is a very flexible system with respect to symbol definition. In order to accurately interpret the results of another researcher's work that utilizes design notation, that researcher must provide a legend that defines the meaning of the symbols. The elements of design notation are:


· “O” is the symbol for an observation or measurement.
· “X” is the symbol for a program or treatment group.

· The “Groups” (program and control) are each given their own line for their notation symbol(s).
For example, if there are three lines there are three groups.

· “Assignment Groups”- At the beginning of each line you will see letters (called notation symbols), the first letter describes how the group was assigned:

R= RANDOM ASSIGNMENT
N= NONEQUIVALENT GROUP DESIGN
C= CUTOFF POINT FOR ASSIGN

Note: If you do not see one of the above three letters on a notation line and the line begins with an “O”, that line indicates a nonequivalent group.


Experimental (Notation)Designs and Their Meaning
"To understand is to perceive patterns." Isaiah Berlin, Historical Inevitability

There are three types of experimental designs. They are:
* Pre-experimental designs
* True experimental designs and
* Quasi-experimental designs.
Pre-experimental designs lack random assignment to the program group and the control group.This design illustrates some inherent weaknesses in terms of establishing internal validity. The better designs are called true experimental designs and quasi-experimental designs. True experimental designs are more complex and use randomization and other techniques to control the threats to internal validity. Quasi-experimental designs (Trochim, 2006) are special designs for use in the approximation of true experimental control in nonexperimental settings. The closer your nonequivalent group approximates a true experimental population the stronger the internal validity.

Pre-experimental Designs and Their Meaning
Pre-experimental Designs
On the surface, the design below appears to be an adequate design. The subjects are pretested, exposed a treatment, and then posttested. It would seem that any differences between the pretest measures and posttest measures would be due to the progam treatment.


The One-Group Pretest-Posttest Design
However, there are serious weaknesses in this design. With the exceptions of selection and morality threat to internal validity, which are not factors due to the lack of a control group, this design is subject to five other threats to internal validity. If a historical event related to the dependent variable intervenes between the pretest and the posttest, its effects could be confused with those of the independent variable. Maturation changes in the subjects could also produce differences between pretest and posttest scores. If paper-and pencil measures are used on a pretest and a different test measure was used on the posttest, a shift of scores from pretest to posttest could occur resulting in a testing threat. Regardless of the measurement process utilized, instrumentation changes could produce variation in the pretest and posttest scores. Finally, if the subjects were selected because they possessed some extreme characteristic, differences between pretest and posttest scores could be due to regression toward the mean.
In all of these cases, variation on the dependent variable produced by one or more of the validity threats could easily be mistaken for variation due to the independent variable. The fact that plausible alternative explanation can not be ruled out makes it very difficult to say with any kind of confidence the treatment given caused the observed effect.
The next pre-experimental design involves comparing one group that experiences the treatment with another group that does not.
Experimental group: X O
Control group: O
In considering this design, it is important to recognize that the comparison group that appears to be a control group is not, in the true sense, a control group. The major validity threat to this design is selection. Note that no random assignment (omission of the letter "R") is the indicator that the comparison group nonequivalent. In the above design, the group compared is picked up only for the purpose of comparison. There is no assurance of comparability between it and the experimental group. For example, we might wish to test the impact of a new type of math test by comparing a school in which the program exists with one that does not have the program. Any conclusions we might reach about the effects of the program might be inaccurate because of other differences between the two schools.
Despite their weaknesses, pre-experimental designs are used when resources do not permit the development of true experimental designs. The conclusions reached from this type of design should be regarded with the utmost caution and the results viewed as suggestive at best (Dooley, 1990).

True Experimental Designs and Their Meaning
True Experimental Designs
Probably the most common design is the Pretest-Posttest Group Design with random assignment. This design is used so often that it is frequently referred to by its popular name: the "classic" experimental design. In a true experimental design, the proper test of a hypotheses is the comparison of the posttests between the treatment group and the control group.

Experimental group: R O X O
Control group: R O O
This design utilizes a control group, using random assignment to equalize the comparison groups, which eliminates all the threats to internal validity except mortality. Because of this, we can have considerable confidence that any differences between treatment group and control group are due to the treatment.
Why are internal threats to validity removed by this design? History is removed as a rival explanation of differences between the groups on the posttest because both groups would experience the same events. Maturation effects are removed, because the same amount of time passes for both groups. Instrumentation threats are controlled by this design because although any unreliability in the measurement could cause a shift in scores from pretest to posttest, both groups would experience the same effect. By removing threats to internal validity you maintain equivalence between the groups. This enables you to conclude with a high degree of confidence that your treatment caused the observed effect and not some alternate plausible explanation.
With respect to regression, the classic experimental design can control for regression through random assignment of subjects with extreme characteristics. This ensures that whenever regression does take place both groups will equally experience its effect. Regression toward the mean should not, therefore, account for any differences between the groups on the posttest. Randomization also controls for selection threat to internal validity by making sure that the comparison groups are equivalent.

Another true experimental design is the Solomon Four-Group Design which is more sophisticated in that four different comparison groups are used.
Experimental group 1: R O X O
Control group 1: R O O
Experimental group 2: R X O
Control group 2: R O

The major advantage of the Solomon design is that it can tell us whether changes in the dependent variable are due to some interaction effect between the pretest and the treatment. For example, let's say we wanted to assess the effect on attitude about police officers (the dependent variable) after receiving positive information about a group of police officers' community service work (the independent variable). During the pretest, the groups are asked questions regarding their attitudes toward police officers. Next, they are exposed to the experimental treatment: newspaper articles reporting on civic deeds and rescue efforts of members of the police department.

If treatment group 1 scores lower on the attitude test than control group 1, it might be due to the independent variable. But it could also be that filling out a pretest questionnaire has sensitized people to the difficulties of being a police officer. The people in treatment group 1 are alerted to the issues and they react more strongly to the experimental treatment than they would have without such pretesting. If this is true, then experimental group 2 should show less change than experimental group 1. If the independent variable has an effect separate from its interaction with the treatment, then experimental group 2 should show more change than control group 1. If control group 1 and experimental group 2 show no change but experimental group 1 does show a change, then change is produced only by the interaction of pretesting and treatment.

When using the Solomon Four-Group Design our concern with history and maturation effects is usually only in terms of controlling their effects. The Solomon design enables us to make a more complex assessment of the cause of changes in the dependent variable. However, the combined effects of maturation and history can not only be controlled but also measured. By comparing the posttest of control group 2 with the pretests of experimental group 1 and control group 1, these effects can be assessed. However, our concern with history and maturation effects is usually only in terms of controlling their effects, not measuring them.

The Solomon design is often bypassed because it requires twice as many groups. This effectively doubles the time and cost of conducting the experiment. Many researchers decide that the advantages are not worth the added cost and complexity (Graziano and Raulin, 1996).

Social Researchers
We cut nature up, organize it into concepts, and ascribe significances as we do, largely because we are parties to a "contentious group of truth seekers" that agrees to organize it in this way - an agreement that holds through the research community and is codified in the patterns of our language of research.

Our challenge as "truth seekers" is to see things as they are and ask why? Hopefully our solutions will have a positive effect on change and not be adversely affected by it.
David Abrahams

Bibliography
Campbell, Donald T and Julian C Stanley
Experimental and Quasi-Experimental Designs for Research, Rand McNally 1966
Graziano, Anthony and Raulin, Michael
Research Methods A Process of Inquiry Longman,Inc. 1996
Howard, George
Basic Reasearch Methods in the Social Sciences Scott, Foresman and Company 1985

Trochim, William, M.K.
Social Research Methods Available at:http://www.socialresearchmethods.net


(Electronic Version): StatSoft, Inc. (2007). Electronic Statistics Textbook. Tulsa, OK: StatSoft.
WEB::http://www.statsoft.com/textbook/stathome.htm.