In 2009, Elinor Ostrom got her 1/2 of the Nobel prize in economics "for her analysis of economic governance, especially the commons." She showed how communities can solve the problem of
the tragedy of the commons outside of the typical framework of private property laws and market-based exchanges. Essentially, Olstrom showed that communal property rules can be effectively enforced by community norms and various informal social control mechanisms, including non-cooperation, frowning upon, shaming, ostracizing, and etc.
Here's a crazy idea: What if we consider the totality of women's sexual and reproductive capacity as common property. That is, the community as a whole (men and women) owns and exploits this property for propagating itself into the future. As any other common property, the reproductive capacity is susceptible to the tragedy of the commons.
The problem arises when, e.g. a male sexual predator acting out of his self-interest, forces sex on as many females as he physically can. Others follow, and as the result, females withdraw sex from other males, depleting the total common capacity.
One solution to the problem is marriage, which in this model would be equivalent to private property. That is, the institute of marriage sanctified and enforced by religion and law prevents predation and stabilizes supply of sex/reproduction to the community.
Another solution would be a market-like mechanism, where women are compelled to trade sex for essential commodities in order to survive in a low-resource environment, e.g. avoid starvation for self and children.
Paradoxically, negative sex/reproduction effects caused by a breakdown in law and order and subsequent sexual predation can be compensated by starvation. (would this be a reasonable way to model Russia in the 1990s?)
A completely alternative strategy along the Ostrom's lines would be community rules that make sexual predation highly undesirable. Under the circumstances, and considering auxiliary human rights norms, the disappearance of marriage would not result in sexual predation and depletion of sex stocks. (This would be a good way to model the current situation in Western Europe). Remarkably, an influx of sexual predators insensitive to community rules (e.g. immigration) can destroy an Olstrom equilibrium, unless the community starts enforcing its norms through formal methods.
Overall, the model can show how different societies avoid a sex-related tragedy of the commons, depending on community norms (endogenous), the state of marriage (endogenous), income levels (exogenous), criminal prosecution of sexual predation and human rights violations (endogenous).