The aim of this study was to examine the Zoroastrians of Yazd, Kerman and Tehran to determine whether or not they differed from each other genetically and from the host population of Iran; to study the Parsis and Iranis - Zoroastrians Who had migrated to India in the 7th Century A.D., and compare the results with those of neighbouring Indian populations. It was hoped to obtain a large number of samples in order to make accurate comparisons, but, owing to the contemporary complex political situation, this proved impossible. Attempts were made to explain the variants in terms of present day demo graphic theories but were hampered by the paucity of published data. Blood, serum and isoenzyme group examinations were made. Serological and electro0ioretic techniques were used to determine ABo, MNSs, Rh, Kell, Duffy, KP, haptoglobin, adenylate kinase, acid fiiosphatase, esterase D and 0ios0ioglucanutase factors in a total of 469 Zoroastrians. Demographic features of contemporary Zoroastrians were studied and the results compared with those of Iranians and Parsis. (No demographic data was available for the Iranis of India.) This revealed that the fertility ratio of the Zoroastrians is lower and present day infant mortality higher than those for the latter groups. Serological test results together with the demographic findings suggest that the long practise of consanquinial marriage may account for the differences which we can observe today.

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The purpose of this thesis is to present a different approach to the formulation of differential equation mathematical models for interacting populations. It does this through considering a geometric method. The solution to the differential equations are forced, through theuformulation, to lie on the surface of well known three-dimensional shapes. It is this that allows detailed analysis of how, and why, the solution of the equations behave as they do. The thesis firstly reviews some of the skills and techniques used in the formulation and alysis of differential equation models to give a background for some of the analysis used the geometric approach to modelling. The geometrical approach is then presented using two three-dimensional surfaces, the ellipsoid and the torus. Also examined is an extension of the basic shape to higher dimensions. Using the three-dimensional shape as a reference, a four-dimensional representation is formulated. This increase in the number of variables in the model allows more situations to be modelled. The thesis concludes by discussing the use of the type of model produced by the geometric approach by addressing some of the advantages and disadvantages of this approach. It ends with some extensions to this study of geometric models for future work.

This thesis focuses on rural-urban migration in Iganna, an ancient Yoruba kingdom located fifty miles west of 0yo in Nigeria. The fieldwork on which this thesis is based took place in Iganna and partly in Ibadan and Lagos between April 1974 and October 1975. The central hypothesis which is put forward in the thesis is that the present-day rural exodus to the urban centres (especially by young people) cannot adequately be accounted for in terms of a 'quest for money' explanation, or, more generally, in terms of formal maximisation theories. The root of this problem, it is argued, lies in the radical changes in the relations of production within the traditional kin-based household units since the inclusion of farm produce in long-distance trade, with the result that farmers become increasingly dependent on/indebted to the middle traders (these are usually their womenfolk) and the hired labourers (these are men from outside Yorubaland). Inherent in this quantitative expansion of commercial farming is a qualitative decrease in social solidarity in the more traditional Yoruba rural communities. The first part of the thesis examines the present-day migration phenomenon as it presents itself in Iganna. While the town has been drained of large numbers of its young people who have been emigrating to the cities since the 1950s, immigration into the area has taken place by Yoruba farmers from other towns, by Fulani pastoralists and by farm labourers from outside Yorubaland. Interviews and questionnaire results concerning the reasons for emigration reveal that most people hold the opinion that there is no money in farming, while emigration to the cities holds the promise of a better and more affluent life. Research into the occupations and living conditions of the people concerned, however, did not fully support such explanations. In the cities the majority of the Iganna migrants live in relative poverty, while in Iganna there are farmers, albeit mainly non-native, who realise good money returns in cash-cropping; although it is true that the majority of the Iganna farmers are chronically hard-up for money. In the second part of the thesis the system of agricultural production in Iganna is examined with why it is unrewarding. A model of the traditional system of agricultural production is presented which explains how farmer- householders used to exert control both over the allocation of their produce and over their dependent co-producers. An analysis is made of the modern changes in agricultural production which were triggered off by the inclusion of farm produce in the external trade with the distant urban markets. In the new system of production farmers no longer depend on their chiefs as patrons and creditors. Instead, their womenfolk who have now become the middle traders in farm produce provide them with credit. Farmers can no longer obtain the assistance of their own household dependants, especially sons and debt-labourers, in order to increase their production. Instead they have to pay for the services of migrant labourers. Hence farmers tend to find themselves socially at the loser's end of the modern system of production, even when they make profits. While the traditional town environment in Iganna tends to disguise these reversed relations of production, it also inhibits farmers from modernising their system of production. At the some time Government policies and initiatives with regard to agriculture have usually proved to be inadequate in coming to grips with the real conditions in which agricultural production is caught in the rural areas. Hence the discrepancies between present-day agricultural production and the rapid social changes in most other domains tend to become more pronounced as time goes on, thus precipitating the large-scale emigration from the rural towns like Iganna to the cities.

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