The hypothesis that the family, whether of monogamous or of polygamous organization, was preceded by a state of unrestricted sexual intercourse, so-called agamy or promiscuity, is, however, as was remarked above, based not only on the fact of maternal descent and of the Malayo-Polynesian method of designating ages, but also on that of group-marriage. In this form of marriage, a number of men marry in common a number of women. This is interpreted as a transitional stage between an unrestricted sexual intercourse within the tribe and the limited marriage unions of later times. At first glance, indeed, this might appear probable. In order, however, to decide whether such a transition could take place, and how it might occur, we must first of all consider the relation which group-marriage sustains, among the peoples who practise it, to the other forms of marriage. It then appears at once that it is a particular form of polygamy. True, it is not identical with the form of polygamy most familiar to us, in which one man possesses several wives. But there is also a second form, which, though less frequent, is of greatest importance for an interpretation of group-marriage. One woman may have several husbands. The two forms of polygamy may conveniently be called _polygyny_ and _polyandry_, and these terms should always be distinguished in any attempt at a precise account of polygamous marriage. Polygyny is very prevalent even in our day, occurring particularly in the Mohammedan world, but also among the heathen peoples of Africa, and in other regions as well. It was likewise practised by the ancient Israelites, and also by the Greeks, although the Indo-Germanic tribes for the most part adhered to monogamy from early times on. Polyandry is much less common, and is, indeed, to be found only among relatively primitive peoples. It occurs in Australia and, in the southern part of Hindustan, among the Dravidians, a tribe of people crowded back to the extreme end of the continent by peoples who migrated into India; it is found also far in the north among the Esquimos of Behring Strait and among the Tchuktchis and Ghilyaks of Siberia, and, finally, here and there in the South Sea Islands.