Based upon a simple model of interactions between two groups, the people in those groups will choose among six options depending on their relative populations, resources, and how much they value people, happiness, longevity (how long the population can survive), and the carrying capacity of their environment (the maximum number of people that can consume a given amount of resources per person).
The first option (isolation) has each group and its resources effectively isolated from the other group and its resources, and the other five involve one or both groups having access to all of the resources. Both groups can share their resources (sharing), which averages their consumption patterns (amount per person and how fast it grows). Group 1 can kill off Group 2, keeping all resources for itself (extermination 1), or Group 2 can do the same to Group 1 (extermination 2). The last two options involve the groups living together, with one dominating the other by imposing its consumption pattern on the other (dominance 1 or dominance 2).
If the two groups and their resources are roughly the same size and at or near their carrying capacity, then extermination 1 and extermination 2 each have roughly a 50% chance of being chosen, with practically no chance of any other option. If they each have more resources than people to consume them, then isolation, sharing, extermination 1, and extermination 2 will each have a 20% chance of being chosen; and dominance 1 and dominance 2 will each have a 10% chance of being chosen.
Where one group is much larger than the other group, isolation has the same chance (25%) of being chosen as sharing, extermination of the smaller group by the larger group, and dominance of the smaller group by the larger group. This is mostly due to the larger group having overwhelming power compared to the smaller group, and is independent of how close each group is to its carrying capacity.
The probabilities I've quoted are approximate averages of simulated groups, with each group "member" and each simulation varying from the average such that at any given time one option may dominate the others. In reality, I expect that all options will be attempted, perhaps simultaneously. I introduced this model in part 3 of my BIOME novel, and will explore its implications in the remaining books as a critical aspect of the plot. Here and in my other writing, I intend to use it as a tool for exploring real-world events, and to test it in the process.
Two predictions of the model are particularly relevant to current events, particularly those involving conflict and the potential for conflict between a large group and a small group, such as we've seen recently in terrorist attacks. Viewed from the perspective of the smaller group, there is a 25% chance of being physically destroyed by the larger group, and a 75% chance of losing cultural purity (total control over happiness and longevity as determined by consumption). To eliminate these threats, isolation can be re-established (accompanied by adequate resources), or full control over the larger group can be achieved by domination or by killing its members. Each alternative requires a huge increase in power, ideally in excess of the power available to the larger group, and we can realistically expect the acquisition of such power to be an early step in the process of pursuing one or more of these courses of action. Interestingly, the same actions that deal with these threats from the larger group may also be used to pose a threat to the larger group (and would be perceived as such by that group, regardless of the smaller group's motivation, thus making more likely the extermination option being taken by the larger group).
Of the two threats perceived by the smaller group, loss of cultural purity is the largest (by a factor of three). If this wasn't an issue, then the extermination threat might be addressed by improving the chances of sharing or domination. Where it is non-negotiable, then isolation is the most humane option. Isolation has been crudely implemented in the past through establishment of penal colonies; but, since the world is currently close to its resource limits, it is practically impossible. Note that space travel would be an option for isolation if habitable planets were already available and reachable, but any settlements in the foreseeable future would be operating dangerously close to their carrying capacities with additional risks to life that would require new consumption patterns and associated cultural adjustments. Incarceration, an extreme form of domination, is commonly used as an alternative to extermination, but of course it is the embodiment of cultural loss for a group that is markedly different from the dominant group.
As our planet changes its requirements for survival with the ecological disruptions of climate change, raw resource depletion, and species extinctions, I expect we will all perceive ourselves as parts of small groups struggling to adapt while avoiding extermination. We will also need to see other species as something other than other groups that can be exterminated, since they and the services they provide embody the "resources" that we need to survive. Our consumption patterns, which are major components of our cultures, will need to be more flexible than ever in light of these conditions; and above all else, we must adjust our values so that our preferred options are more aligned with extending longevity and minimizing death.