半農半牧民の生態学的考察

Abstract

The Iraqw inhabit chiefly the Mbulu District in the north Tanzania, the majority of the tribe living in the pleateau grassland zone at an altitude of 1900-2100m above the Rift Wall. Their total population amounts to over 130, 000. The Iragw cultivate crops, mainly maize and sorghum, while they raise cattle, goats, sheep, and a few donkeys.In my previous paper (1969), I investigated the production mode of the Iraqw, and concluded that little organic relationship was to be found in their subsistence economy between their crop-cultivation and stock-raising. Consequently I propose a distinction between “agrico-pastoral”, where little organic relationship exists between the two, and “mixed farming”, where the two elements form an organic whole.The “agrico-pastoral” Iraqw consequently exhibits an ecological adaptability different from that of the agricultural Bantu group or the pastoral Nilotic group, possesing their own modes of territorial expansion and land-use. This may also be contrasted with that of “mixed farming”, where cropcultivation and stock-raising form an organic whole. The examination of tribal socety from ecological viewpoint helps to fill out the general picture in details which are easily overlooked when viewing it simply from the standpoint of social structure. By considering a local society from this ecological viewpoint, it is possible to gain a broader insight into tribal society, which in turn helps to clarify intertribal relations. Further it is possible that such an assessment will provide a key to the historical process of tribal society.I spent about one year from November, 1964 to October, 1965 in the Mbulu District of the north Tanzania, as a member of the Kyoto University Africa Scientific Expedition Team. During this time, the investigation base was originally built in Giting area, which opens onto the northern face of Mt. Hanang (3418m alt.). The present paper is based on the anthropological field work of the Iraqw at that time.In this paper, I have endeavored to describe the habitat, migration, settlement and land-use of the Iraqw in the Giting area. I have shown their connection with other tribes, in particular the Datoga, and have put my own theory on the characteristics of the Iraqw “agrico-pastoral” society as seen from an ecological point of view.1) The relationship between the agricultural element and the pastoral element in these two differing cases may be expressed by the following formulae:* “agrico-pastoral”......c=p⋅a* “mixed farming”......C=a/pa: agricultural elementp: pastoral elementc or C: constantIn Iraqw society, a tends to expand in plateaugrassland areas, p in wooded savanna areas. In contrast to this is the case of “mixed farming” where a and p are inseparably bound together, so that they are in direct proportion to one another. In either case, one may distinguish a number of different types according to the difference of circumstances, and the constant c or C changes accordingly.Here I am content to propose this as a hypothesis for the purpose of characterizing the Iraqw society. Subsequent investigation of materials will allow me to clarify the problem in greater detail.2) That the agricultural and pastoral elements in the Iraqw society are in inverse proportion to one another tends to produce certain special characteristics in their intertribal relations. That is to say, in their pastoral facet the Iraqw are connected with the pastoral Datoga tribe, while in their agricultural facet they are connected with the Bantu agricultural tribes. This is closely connected with the change in the ecosystem. This territorial expansion by the Iraqw affords a clue to us in the study of their historical evolution.