We have seen that slavery cannot exist to any considerable extent among peoples with closed resources. But even among peoples with open resources it is not always found. Slaves perform the drudgery for their masters; therefore they are not wanted where little drudgery has to be done, or in other terms, slavery is not likely to exist where subsistence is difficult to acquire. Where men subsist by highly skilled labour, there can be little use for slaves; for the slaves cannot be made to perform such labour; and the little unskilled labour that is wanted is not profitable enough to admit of the keeping of slaves, who would have to be fed by the produce of their [[423]]masters’ work. This is the principal reason why slavery hardly ever occurs among hunters, and one of the reasons why the Eskimos do not keep slaves.
We find thus that, generally speaking, the keeping of slaves is economically profitable to peoples with open resources among which subsistence is easily acquired, and to such peoples only. But there are several secondary causes, internal and external, which bring about that slaves are sometimes kept by peoples with closed resources, or by peoples among which subsistence is difficult to procure, and that on the other hand slavery is sometimes absent where resources are open and subsistence is easy to acquire.
Among the secondary internal causes we have noted in the first place the condition of women. There is no use for slaves, where all disagreeable work can be, and is performed by the weaker sex; Australian and Melanesian women supply the place of slaves. On the other hand, where the women hold a high position, and the men are desirous of relieving them of a part of their task, slavery is likely to arise sooner than otherwise would be the case.
Commerce probably exists among all savages. Even the Australian tribes mutually exchange rare kinds of earth for painting their bodies, and similar objects. But commerce has only a social importance, where the articles exchanged are manufactured goods in the widest sense, including e.g. fish and agricultural products, in a word all articles the production of which requires a considerable amount of labour. Then the freemen who devote themselves to commercial pursuits want others to perform the common labour for every-day subsistence; moreover the preparing of the articles of trade requires more labour than would otherwise be wanted. And last, but not least, commerce leads to the development of wealth and luxury; slave labour is now wanted to provide the owner not only with the necessaries, but with the comforts of life. Commercial tribes in the widest sense,—including 1º tribes which exchange native produce for foreign manufactures, 2º tribes which themselves produce and export manufactured goods in the common, restricted, sense, 3º tribes which carry on a transit-trade,—are therefore far more likely to keep slaves than self-sufficing tribes. [[424]]
We have seen that subjection of women is sometimes a substitute for slavery. Another substitute is subjection of tribes as such. This subjection occurs only, so far as savages are concerned, where peculiar circumstances render it possible: among pastoral tribes, which subject their neighbours to whom they are superior in military qualities, and in Oceania, where the limited area prevents the conquered from receding. Where a tribe subjected as such pays a tribute to the conquerors and performs services for them, there is not so much need for enslavement of individuals belonging to the vanquished tribe.
People who live from hand to mouth have less use for slaves than those who preserve food for the time of scarcity. The preparing of this food may require much labour which is very fit to be performed by slaves. We have seen that such is especially the case on the North Pacific Coast of North America.
Slaves are sometimes kept for non-economic purposes.
Warfare plays a great part in savage life, and we have found that the requirements of warfare sometimes prevent, but in other cases further the rise of slavery. Many savage tribes increase their population by introduction of foreign elements. This may be done for two reasons: men are wanted either for labourers or for warriors[8]. In the former case the introduction of aliens leads to slavery in its most general form of extratribal slavery. When warriors are wanted, slavery is not the most appropriate form; adoption of foreigners, such as was for instance practised by the Iroquois, answers the purpose better, because a man who enjoys the common privileges of a member of the tribe is more reliable in war than a slave. In such case militarism may prevent the rise of slavery, because all available men are wanted in war and have therefore to be placed on a level with the tribesmen. But where superior military qualities of a tribe render the employment of slaves in warfare (most often in the lower ranks of the army) possible, slaves are sometimes kept mainly for military purposes, especially [[425]]where prejudices of race or colour prevent the tribe from adopting the foreigners. Then militarism furthers the growth of slavery; for slaves would perhaps not be wanted, if they did not serve as warriors.
Slaves may also be kept as a mere luxury. The possession of many slaves, like other property, everywhere tends to give the owner influence and reputation. Yet he most often also derives material profit from his slaves, namely from the total number of them, even where some of them do not perform productive labour. Only in a few cases does the sole use of slaves appear to consist in augmenting their owners’ influence and reputation. This occurs among some pastoral tribes, where the rich are able to support a large number of unproductive labourers. But here the military use of slaves has perhaps co-operated in establishing slavery.
In the beginning of this paragraph we have spoken of external causes.