The Indigenous Australian Marriage Paradox: Small-World Dynamics on a Continental Scale

Ethnographies of Indigenous Australian language groups suggest that their populations were consistently small, averaging perhaps 500 people each, while classical models of their kinship systems consistently embody endogamous marriage as both a norm and a logical requirement. While geneticists are concerned about the potentially lethal effects of inbreeding depression in small populations, paleodemographers argue that reproductively closed small populations, whether humans or other species, are doomed to extinction due to stochastic variations in birth rates and sex ratios. How then did Australia foragers avoid extinction and persist for 40,000 years and more if each was reproductively closed as in models of prescriptive endogamy? We introduce a mathematical model of Aboriginal descent, marriage and kinship that is reproductively open rather than closed, show how the openness articulates with traditional closed kinship models, and demonstrate how the resulting system might maintain dynamic population stability despite internal and external stresses that might otherwise lead to extinction. The mathematical model demonstrates how each language group creates and maintains a local cluster in the space of a large “small world” of continent-wide marriage connections that articulate through common features of social structure and whose variants are likely to have adaptive significance in relation to sites and periods of scarcity or resource