Anthropologists differ over the importance of bilateral groups and relationshp for the formulation of endogamous and exogamous regulations. G.P. Murdock, a major figure in comparative kinship studies, understood the kindred as analogous to a unilineal descent group, and maintained that it would be inherently exogamous in order to avoid isolation and enter into exchanges and alliances with complementary groups (Murdock 1949). This position is supported by evidence from the Ju/'hoansi foragers of the Kalahari, who uphold a prohibition on marriages among second cousins. However, J.D. Freeman, who conducted a landmark study of the Iban, abilateral society in Malasia, observed that marriage within the kindred to first and second cousins accounted for over 75% of all unions. (Freeman 1968). He concluded that bilateral organization involved a different dynamic from unilineal forms because of their multistranded and overlapping membership structures. Inmarriage was beneficial because it kept social relations within the kinship network from becoming too broadly diffused. Exogamy was not particularly essential, because the kindred structure ensured wider social integration without the need for marriage exchanges.
The Murdock/Freeman debate can be assessed in terms of the history of cousin marriage taboos in European history. While some variation is apparent, (see US state legislation concerning close marriages), Western cultural attitudes towards cousin marriage are generally negative and expressed in terms of dire moral and medical concerns in spite of the low genetic risks involved. These taboos were not always prevalent. The basic Germanic institutions, from which contemporary bilateral patterns have developed, allowed and even showed a preference for close marriages. The changes in attitudes are difficult to document or trace, but are due in part to the influence of the Church, which during the early Middle Ages, instituted a ban on marriages within seven Germanic degrees of consanguinity, or sixth cousin range (Goody 1983:56). In this legislation, the Church does not seem to have be following or enforcing traditional European custom and practice. Violations of the rules and requests for dispensations abounded, especially since most people did not maintain the detailed genealogies that would have been needed to identify distant relatives. (They would have had to trace all of the descendents of 64 pairs of great-great-great-great-great-grandparents.) The Church itself justified its policy on the basis of scripture, through a questionable interpretation of Chapter 18 of Leviticus. Its real motivation may have been to discourage the consolidation of wealth and power supported by endogamy within the upper levels of the nobility (Goody 1983:134-146).