The practice of seizing women from the enemy as trophies, gave rise to a form of ownership-marriage, resulting in a household with a male head.

This was followed by an extension of slavery to other captives and inferiors, besides women, and by an extension of ownership-marriage to other women than those seized from the enemy.
The outcome of emulation under the circumstances of a predatory life, therefore, has been on the one hand a form of marriage resting on coercion, and on the other hand the custom of ownership.

The two institutions are not distinguishable in the initial phase of their development; both arise from the desire of the successful men to put their prowess in evidence by exhibiting some durable result of their exploits.

Both also minister to that propensity for mastery which pervades all predatory communities.

From the ownership of women the concept of ownership extends itself to include the products of their industry, and so there arises the ownership of things as well as of persons.
In this way a consistent system of property in goods is gradually installed.