Many post apocalyptic novels explore the issue of different partnership arrangements between men and woman. This trend seems to have faded in the 1980s, with any alternative arrangements being (from an authorial point of view) viewed as aberrant rather than exploratory. The examples are so numerous, and so varied in their seriousness, I will avoid going into specifics.
This somewhat begs the question of: Why do we have monogamous societies at all?
Historically, and from what we know pre-historically, monogamy has not been the norm. 85% of societies within the anthropological record allow multiple marriages by men. Additional wives were (are) often a status symbol. Even societies that are otherwise highly egalitarian on their surface practice polygynous marriage. The Cheyenne, dominant horse-tribe in the American Southwest in the early and middle portions of the 19th century used their multiple (after the third one) as an enslaved work force for those with enough wealth to maintain them.
Looking at the roots of Western Society, in the Jewish (Old Testament) Torah, many of the early patriarchs (Abraham, Jacob, David, and Solomon) had many wives, and there was no strict regulations against it. Within the Jewish faith, the strict ban on polygynous marriage only came 1000 years ago within the Ashkenazi Jewish sect. As an accident of history, the Ashkenazi are the dominant Jewish group in the modern world so we tend to associate Judaism with monogamous marriage.
A recent study has looked at some of the advantages of monogamy in a study of cultural cross comparisons.
Joseph Henrich, Robert Boyd, and Peter J. Richerson, Royal B. Society, March 5, 2012 367 (1589) 657-669; doi:10.1098/rstb.2011.0290
In suppressing intrasexual competition and reducing the size of the pool of unmarried men, normative monogamy reduces crime rates, including rape, murder, assault, robbery and fraud, aswell as decreasing personal abuses. By assuaging the competition for younger brides, normative monogamy decreases (i) the spousal age gap, (ii) fertility, and (iii) gender inequality. By shifting male efforts from seeking wives to paternal investment, normative monogamy increases savings, child investment and economic productivity. By increasing the relatedness within households, normative monogamy reduces intra-household conflict, leading to lower rates of child neglect, abuse, accidental death and homicide.
I am not completely convinced of all their logic. Many of them sound like nice reasons why monogamy would be more effective. But reality is not always “nice”.
Peter Turchin has noted in his book, Cliodynamics, that the Islamic societies elite turnover tended to be very high, as the elite with a very large number of children, tended to very quickly outgrow the surplus resources of society: much faster than the slow rise and ebb of the general population. The short term advantage to an individual, was also their long term disadvantage.