Zambezia (1977), 5 (ii).RESEARCH REPORTVARIABLES OF POPULATION GROWTHTHIS REPORT DISCUSSES the variables of population growth in a tribal com-munity in the Midlands of Rhodesia. A model of nutritional stress showshow these variables inter-relate to influence birth rate and child mortalityin rural families. The overall analysis suggests that population control iseffected in two ways: either through stress and poverty when the birth ratedeclines and child mortality increases, or through security and economicdevelopment when the birth rate and child mortality decline. The analysisalso shows that the highest birth rate occurs in families where there is asubsistence level of nutrition.We originally put forward these views in 1975' and Mr H. Dunlop in re-viewing this, and other publications, criticized our findings as follows:The major finding of Theisen's work, presented in the two pamph-lets under review, is that there is a simple causal relationshipbetween socio-economic status and family size; this is positivelydangerous. The following is a reasonable summary of the presentstate of research on the topic:In a recent work, Karen O. Mason and her associates reviewed andanalyzed more than a hundred studies on differential fertility inthe developed and developing countries. In this work, the authorspresent the major studies undertaken to measure the effect ofsocio-economic variables on family fertility. The major variablesincluded in the studies were: income, occupation, social and geo-graphic mobility, education, family structure, female labour-forceparticipation, egalitarian maternal relationship, religion and re-ligiosity, value orientation, and family planning. After a carefulexamination of the results of these studies, the authors have foundvery little evidence of uniformity and consistency in the findingsof the studies . . . while modern value orientation and high socio-economic mobility reduce the high fertility, norms and practicesamongst the urban Spirazi, these facts seem to have a positiveeffect on the fertility pattern of the tribal population.2In saying this, Dunlop seems to have completely misunderstood the signifi-cance of the Rhodesian findings, for not only do they agree in general with1 R. J. Theisen, The Exploding Population Problem in the Tribal Trust Lands ofRhodesia (Salisbury, The Tribal Areas of Rhodesia Research Foundation, 1975).2 H. Dunlop, 'The Publications of the Tribal Areas of Rhodesia Research Founda-tion', Zambezia (1975-6), 4, ii, 112, quoting A. A. Paydarfar, 'Socio-cultural corre-lates of fertility among tribal, rural and urban populations in Iran', Social Biology(1975), 22, 151.161162VARIABLES OF POPULATION GROWTHfindings in other countries but they also help to explain these other findings.In particular there are two points I wish to make in connection with thiscriticism.Firstly, the 'simple causal relationship between socio-economic status andfamily size' that he claims to find in my analysis is not in fact there. WhatI argued was that the relationship between family size and socio-economicstatus was a function of systems of stress and security. In other words, anincrease of status does not necessarily lead to security, and it is securitythat is all important. For example, when socio-economic variables such asschool education are associated with 'security' or the lessening of 'stress',then this is generally conducive to a low birth rate, but when the oppositeoccurs then this is generally detrimental to a low birth rate. This can bedemonstrated by a simple education model showing the relationship betweenschool education, wage earnings and birth rate; data from three tribal areasof Rhodesia show that the birth rate in families where the head is educatedbut can only secure low paid employment is significantly higher than thebirth rate of educated family heads who are able to secure highly paid em-ployment. There is, therefore, no simple correlation between birth rate, schooleducation and income, but there is a significant relationship when the threevariables are inter-related in terms of stress and security. Thus, the rela-tionship between socio-economic status and family size (i.e. living childrenborn to the family head and his wife) only becomes comprehensible whenthe variables denoting socio-economic status are inter-related to form amodel which shows how these variables influence the population in termsof security and stress.Secondly, the results of the Rhodesian project do not conflict with thefindings from other countries. In fact the very opposite is true. For example,the Iranian findings, which Dunlop cited, themselves conclude that:Although our tribal sample is not large enough to have our fullconfidence, these observations challenge the generality and univer-sality of the conventional propositions postulating an inverserelationship between fertility and socio-economic status amongdifferent population sectors, at least within a country. One explana-tion may be that in the transitional period among developing popu-lations, the relationship between fertility and socio-economic indicesis curvilinear. In other words, with the rise of socio-economic con-ditions fertility increases, but as socio-economic conditions continuerising, fertility declines. To substantiate this observation, we requiremore detailed historical data.3This observation is fully substantiated by the Rhodesian findings, and isclearly demonstrated by the Nutritional Stress Model now presented. Birthrate does in fact rise with increasing socio-economic conditions until sub-sistence status is reached. Thereafter there is a significant drop with increas-ing socic-economic development.3 Ibid., 161 (my emphasis).R. J. THEISEN163Other comments concerning the Iranian findings are as follows:The direction of the relationship (modern value orientation andsocio-economic mobility) within the rural group in regard to fer-tility and life style is not quite clear. One plausible hypothesisbeing established in fertility-related studies is that the improvementof socio-economic conditions among non urban sectors of develop-ing countries will improve the nutritional conditions of the ruralpopulation and this will reduce child mortality and raise the meannumber of living children.4Once again the Rhodesian findings fully substantiate this hypothesis. Ref-erence to the Nutritional Stress Model shows that rising socio-economicconditions are in fact associated with improving nutrition and this doesresult in reduced child mortality and a rise in the mean number of livingchildren, as is clearly demonstrated below in Figure 1.The main difference between the Rhodesian and the Iranian projects liesonly in the employment of different theoretical premises and measuring scales.Moreover, the 'stress security theory' used for the evaluation and interpreta-tion of the Rhodesian data could perhaps also explain the lack of 'uniformity'and 'consistency' in the Iranian findings. The reason why, for example, 'highsocio-economic mobility reduce[s] the high fertility, norms and practicesamongst the urban Spirazi [but] seem to have a positive effect on the fertilitypatterns of the tribal population', can be explained by the theory if it is shownthat 'socio-economic mobility' produces greater stress in the rural populationby comparison with the urban.Thus, the suggestion that the Rhodesian findings are 'positively dangerous'because they differ from other findings by showing a simple causal relationshipwhere none is supposed to exist, is invalid. The causal relationship is not simplebut based on systems of security and stress; and the two independent sets offindings in question are not different but remarkably complementary. Buteven if the Iranian and Rhodesian findings were basically different, it wouldbe short sighted to arbitrarily dismiss one set of findings as less valid, forwe are dealing with a dynamic human situation which differs from personto person, family to family, community to community, and nation to nation.The only way to break down barriers of prejudice and intolerance is throughresearchŠresearch to discover, investigate and explain these differences, fortruth assumed and knowledge believed without the testing of reality can soeasily lead to the degradation of society.It is our sincere hope that the Rhodesian findings, together with the 'stress-security theory of adaptive behaviour' suggested by these findings, will stimu-late further research and perhaps eventually provide the knowledge whichwill enable us to more effectively control our economic and political destinyfor the benefit of all. What follows is an example of the type of researchwhich should provide greater insight into the complexity of populationgrowth.Rhodesia, in common with most developing countries, is experiencing ahigh population growth rate of 3,6 per cent per annum which means a doub-ling of the population in nineteen years. In order to isolate and investigate* Ibid., 166.164VARIABLES OF POPULATION GROWTHvariables influencing the high birth rate, a family planning survey togetherwith an agro-economic and health survey was administered in the Que QueTribal Trust Land in 1972. Evidence from these surveys shows that the'stress-security' variables influencing the nutritional status of rural families,such as highly productive vlei cultivation, livestock, school education, health,religion, and the residency and wage earnings of working family heads, arealso important variables of population growth.5 It would generally be agreedthat the way in which these variables influence population growth is as fol-lows:In Western societies the higher socio-economic classes have smallerfamilies than the lower classes, and in general the birth rate of theseWestern societies is progressively decreasing with increasing deve-lopment. In an African society where, for economic reasons, familysize is an important source of security and social status, adjust-ment towards a Western social model requires a transition fromsecurity, based on family size, to security based on education,property and money.From this, however, it is sometimes assumed that the head and wife of better-adjusted families, with sufficient education, vlei land and livestock, to achievea standard of nutrition above the subsistence level, will have fewer childrenborn to them by comparison with the husband and wife of maladjustedfamilies whose education, vlei land and livestock are inadequate and whosestandard of nutrition is below the subsistence level. This general assumption,however, is not valid when tested by a Stress Security Model involving theuse of a Nutritional Stress Scale applied to the data of the Que Que survey,6for this model in fact shows that with improving agro-economic conditions,the birth rate and family size actually increase until a subsistence level ofnutrition is reached; and only thereafter is there a decrease in birth rateand family size with improving conditions (see Fig. 1). A statistical test alsoshows that there is no significant difference in family size (i.e. living childrenborn to the head and his wife) when families are categorized as 'below sub-sistence' or 'stressed' or 'above subsistence' or 'secure'. However, a closeexamination of the evidence proves the following:1. The highest birth rate occurs in families who are just at thesubsistence level (i.e. in the third, middle, category (Figure 1);2. In 'below subsistence' families fewer children are born andsignificantly more children die by comparison to 'subsistence'families, and this results in nuclear families which are smallerthan the average; and3. In 'above subsistence' families there is a lower birth rate, inassociation with lower death rate, by comparison with 'subsist-ence' families. This also results in nuclear families which aresmaller than the average.s These variables have been discussed in R. J. Theisen, 'Development in ruralcommunities', Zambezia (1975-6) 4, ii, 93-7.e For a brief description of the model, see ibid; the full details are to be found inmy unpublished paper, 'The Cultivation of Vleis in a Tribal Trust Land' (mimeo).R. J. THEISENFigure 1 . -Ł:SECURITY AND BIRTH RATEHYPOTHESIS: Better adjusted families with adequate education, vlei landand livestock, and who have an above-subsistence standard of nutrition, willhave fewer children than maladjusted families with inadequate education,vlei land, and livestock and who have a below subsistence standard of nutri-tion.ANALYSISStatisticalControlAge of MotherOmission ControlPlural Wives;Widows+ 2+ 1-IChildren of Head and WifeBorn i — -^ ILivint1969-70 Statistics ScaleVLEILANDLIVE-STOCK"sciiooL ~EDUCATIONMean Acres Used byFamily% of Families OwningMean L.U. per Family% of Families OwningStockIndividual Literates% of Heads & WivesLiterateHEALTH10 percentile heightfor age(Boston Standard)% Child MortalitySIGNIFICANCE, EVALUATION AND CONCLUSION: The hypothesis isnot significant as both 'above subsistence' and 'below subsistence' familieshave more or less equal numbers of living children. However, further exami-nation will show that population control can be affected in two ways: eitherthrough systems of stress and poverty when fertility declines and 'child mor-tality' increases; or through systems of security and plenitude when fertilitydeclines and child survival increases.NOTE:' A health survey conducted in the Que Que Tribal Trust Land shows that theheight or age rating of African school children is indicative of Protein Stress and theincidence of disease symptoms when values fall below the 10th percentiie 'Boston Stand-ards' ; see M. Bohdal et. al. 'A comparison of the nutritional indices in healthy African,Asian and European children', Bulletin of the World Health Organisation. (1969),40, 166-76.2 Other variables such as religion and income from employment are also significantlyrelated to nutritional stress and family size. As the influence of these variables, however, isnot linear, a different stress model has been contructed to show these relationships, whichI hope to publish later.166VARIABLES OF POPULATION GROWTHThese conclusions suggest that:Population control can be effected through stress and poverty, orthrough security and economic development; and security variablesinfluencing the nutrition and economic status of the family are im-portant variables of population growth which can be manipulatedto promote economic development and a reduction in birth rate.These findings can be explained from a security and a stress basis. In termsof security, a stress adjustment survey shows that the men and women ofinsecure families with below subsistence levels of livestock and land willgenerally make negative adjustments : these persons orientate their be-haviour in accordance with their children who are their only source ofsecurity. On the other hand, better educated men and women who cultivatevlei land and who possess more than six head of cattle generally make posi-tive adjustments : these persons tend to orientate their behaviour in accor-dance with the amount of livestock and acres of land they possess, andplace less emphasis on family size.It can be assumed therefore, that the husband and wife of insecure familieswill tend to develop unfavourable attitudes to limiting their children whoprovide their only form of security, while the heads of secure families, withvlei gardens and adequate livestock, are more likely to develop favourableattitudes to limiting their children who are no longer a vital source of security.The validity of this assumption has been partly confirmed by data from aFamily Planning Survey which shows that the family planning attitudes ofwomen in families who are above the subsistence level are significantlymore favourable than the family planning attitudes of women in familieswho are at, or below, the subsistence level (at which level attitudes becomeundefined, being neither strongly negative nor positive).These findings agree with the actual situation in respect of the number ofchildren born to the wife, in that significantly fewer children are born infamilies which are above the subsistence level than in those at the subsistencelevel. The lower birth rate in 'below subsistence' families may be associatedwith low fertility induced by nutritional stress and is therefore physiologicalrather than psychological.The influence of the above-mentioned stress-security variables on popu-lation growth can also be explained in terms of stress. Detailed observationsof patterns of population growth indicate the existence of well-developedpopulation growth modes in the community. Years of maximum populationgrowth appear to coincide with periods of general stress and anxiety. Thisis illustrated by Figures 2 and 3, which show a significant increase in birthrate after the prohibition of vlei cultivation by the Lands Inspectorate, andafter the Pearce Commission, respectively.77 The unauthorized cultivation of wet land is illegal according to the NaturalResources (Protection) Regulations; see Rhodesia, Government Gazette, 14 June 1968,Rhodesia Government Notice No. 774.R. J. THEISENFigure 2ECONOMIC STRESS AND BIRTH RATE167HYPOTHESIS: Inspectorate activity directed at removing vlei arable fromcultivation will result in retrogressive development in above-subsistence fami-lies which could, according to the subsistence hypothesis, result in physicaland mental stress sufficient in fact to promote an increase in the birth rate ofthe community to accommodate the threat to the survival of the family. There-fore significantly more children than the expected average will be born inthe community during the year following the prohibition of vlei cultvation.ANALYSIS: VLEI ARABLE DEMARCATIONAgro-Economic Survey,Que Que T.T.L., 1970 and 1972Family Planning Survey,Selukwe T.T.L., 1972SIGNIFICANCE. EVALUATION AND CONCLUSION: The hypothesisis significant at less than ,01 (Kolmororov-Smirnov test).Figure 3SOCIAL STRESS AND BIRTH RATEHYPOTHESIS: The stress and anxiety resulting from the civil disorder atthe time of the Pearce Commission will promote an increase in birth rate.ANALYSIS: CIVIL DISORDER AND BIRTH RATEMonomotapa Township, Gwelo; 1:3 Random SampleAgro-Economic Survey, 1973Year 1971 1972 1973Month Sept.- Nov.- Jan.- Mar.- May- July- Sept.- Nov.- Jan.- Mar.- May- July-Oct. Dec. Feb. Apr. June Aug. Oct. Dec. Feb. Apr. June Aug.Births 2423 1311123 10SIGNIFICANCE, EVALUATION AND CONCLUSION: The hypothesisis significant at less than ,01 (Kolmogorov-Smirnov test). Tension in Gwelobegan to increase in December 1971 before the arrival of the Pearce Com-mission and it continued to increase until the riots of 16 January 1972. Bythe end of January the stress situation appeared to be returning to normal** The sudden rise in birth rate during September and October 1972 coincides per-fectly with the period of maximum stress and anxiety that occurred nine months earlieras a result of the Pearce Commission.168VARIABLES OF POPULATION GROWTHThis suggests the presence of unconscious psycho-physiological causes whichoperate as a survival mechanism when family security and survival arethreatened. In other words a natural survival mechanism involving a toningup of the hormone and nervous system may increase the fertility of thecommunity in response to generalized stress and anxiety. This survivalphenomenon apparently also operates on those at subsistence level when thesurvival of the family is threatened; this undoubtedly accounts for the highbirth rate of subsistence rural families.CONCLUSIONA series of analyses based on the 'Nutritional Stress Scale' suggests thatthe aforementioned security variables interact to establish psycho-physio-logical processes which regulate th& development of attitudes and moti-vation to govern the adjustment of the individual and family and the adapta-tion of the community. The lowest birth rate occurs in the 'above subsistence'families, but if the material and mental security of these families are threat-ened (i.e. by the prohibition of the use of vleis8) this is associated with anincrease in birth rate. The highest birth rate and largest family size occur in'subsistence' families, while in 'below subsistence' families the lower birth rateand smaller family size is apparently controlled by infertility and a high rateof child mortality.University of RhodesiaR. J. THEISEN