show how such different types as polyandry and polygyny arose.

Polyandry, or the union of one woman with several men, is a relatively
rare form of marriage and the family, found only in certain isolated
regions of the world. It is particularly found in Tibet, a barren and
inhospitable plateau north of India and forming a part of the Chinese
Empire. It is also found in certain other isolated mountainous regions
in India, and down to recent times also in Arabia. In none of these
places does it exist exclusively, but rather alongside of monogamy and
perhaps other forms of the family. Thus in Tibet the upper classes
practice polygyny and monogamy, while among the lower classes we find
polyandry and monogamy. In all these regions where polyandry occurs,
moreover, it is to be noted that the conditions of life are harsh and
severe. Tibet is an exceptionally inhospitable region, with a climate of
arctic rigor, the people living mainly by grazing. Under such
circumstances it is conceivably difficult for one man to support and
protect a family. At any rate, the form of polyandry which we find in
Tibet suggests that such economic conditions may have been the main
cause of its existence. Ordinarily in Tibet a polyandrous family is
formed by an older brother taking a wife, and then admitting his younger
brothers into partnership with him. The older brother is frequently
absent from home, looking after the flocks, and in his absence one of
the younger brothers assumes the headship of the family. Under such
circumstances we can see how the natural human instincts which would
oppose polyandry under ordinary circumstances, namely, the jealousy of
the male, might become greatly modified, or cease to act altogether.
Certain other conditions besides economic ones might also favor the
existence of polyandry, such as the scarcity of women. Summing up, we
can say, then, that this rare form of the family seems to have as its
causes: (1) In barren and inhospitable countries the labor of one man is