In connection with the former point it may be inquired what is in each case the status of children born of two slaves, of a male slave and a free woman, of a female slave and a free man, and especially of a female slave and her master. This inquiry will enable us to find, whether and to what extent slaves are merged in the general population.[10]

The manners in which free-born people become slaves may be distinguished according as slaves are acquired from without or within the limits of the tribe. This reminds us of the distinction we have made between extratribal and intratribal slavery. We may inquire then which of these two forms of slavery appears first. If we should find that extratribal is older than intratribal slavery (which does not seem unlikely), we might examine the economic and social conditions under which intratribal slavery can exist.

Extratribal slaves become such by:

1º Capture in war or kidnapping. Here a wide field of research opens itself. Captives, when they are not enslaved, are killed (eaten, sacrificed), or exchanged after peace has been concluded, or ransomed by their countrymen, or adopted into the tribe of the captors. It may be inquired whether any of these modes of treatment can have gradually led to enslavement of the captives (e.g. captives are first adopted, and gradually differentiated from the born members of the tribe: or they are first eaten, then preserved to be eaten later on and in the meantime set to work, and finally employed as slaves and no longer eaten)[11]. Several of these modes of treatment [[429]]coexist with slavery (e.g. some captives are sacrificed and the rest kept as slaves; or slaves are occasionally sacrificed); does this only occur in the early stages of slavery, and indicate that slavery has not yet fully developed? When is slavery an object, and when is it only an incident of warfare? A remarkable phenomenon, worth a close investigation, is the occurrence of extratribal slavery or adoption of aliens together with a preventive check on population (infanticide, abortion)[12]. When captives are enslaved, it is worth inquiring in what manner they are distributed among the captors; this will have a strong influence on the division of wealth.

2º Purchase. The prices paid for different classes of slaves show what slaves are most desired (men or women, people of different ages or nationalities). The slaves sold have often been captured by the sellers; but it also occurs that people are sold by their countrymen, especially criminals. Here we may notice the influence of the slave-trade on penal law; people are probably often sold abroad, who otherwise would have been killed or expelled from the community.

Intratribal slaves become such (so far as we know) in the following ways:

1º For non-payment of a debt. Here the general treatment of debtors and the extent to which the rights of creditors are acknowledged by the community are worth examining. Debtor-slaves have often, but not always, a right to become free by paying off the debt[13]. In some cases the creditor [[430]]does not keep the debtor as a slave, but recovers his money by selling him abroad[14].

2º As a punishment, either directly, or when the wergild is not paid. This subject might be treated in connection with Professor Steinmetz’s investigations of early penal law. Criminals often become slaves of the chief or king; a study of this matter would lead to an inquiry into political institutions at large.

3º By marrying a male or female slave. Here we may inquire where and to what extent connubium between free people and slaves exists.