r/K selection theory describes two environmental extremes, and the strategies a population will produce to exploit each extreme. As a result of these strategies, each of these two environments will produce a very particular psychology in the individuals exposed to them.
The first environment an organism may face is the presence of freely available resources, which is referred to as an r-selective environment. This most often occurs when a predator keeps a population consistently lower than the carrying capacity of its environment. Just as rabbits do not strip their grassy fields bare due to the predation they endure, the r-strategy is designed to exploit an environment where resources are freely available, everywhere.
In r-selection, those individuals who waste time fighting for food will be out-reproduced by pacifists, who simply focus upon eating, and reproducing. Fighting also entails risks of injury or death – risks which are pointless given the free availability of resources everywhere. Hence this environment will favor a tendency towards conflict avoidance, and tend to cull the aggressive and competitive. It will also evolve tendencies towards mating as early as possible, as often as possible, with as many mates as possible, while investing as little effort as possible rearing offspring. Here, there are unlimited resources just waiting to be utilized, and even the most unfit can acquire them. As a result, it is more advantageous to produce as many offspring as possible, as quickly as possible, regardless of fitness, so as to out-reproduce those who either waste time producing quality offspring or waste time competing with each other.
In the other environment, a population exists at the carrying capacity of its environment. Since there is not enough food to go around, and someone must die from starvation, this will evolve a specific psychology within such a species.
Termed a K-type psychology, or K-Selected Reproductive Strategy, this psychology will embrace competitions between individuals and accept disparities in competitive outcomes as an innate part of the world, that is not to be challenged. Since individuals who do not fight for some portion of the limited resources will starve, this environment will favor an innately competitive, conflict-prone psychology. Study shows, such a psychology will also tend to embrace monogamy, embrace chastity until monogamous adulthood, and favor high-investment, two-parent parenting, with an emphasis upon rearing as successful an offspring as possible. This sexual selectiveness, mate monopolization, and high-investment rearing is all a form of competing to produce fitter offspring than peers. This evolves, because if one’s offspring are fitter than the offspring of peers, they will be likely to acquire resources themselves, and reproduce successfully.
R/k selection theory is not the best way of understanding human evolution. The best way is through the theory of natural selection. R/k selection theory is just a helpful model.
Because it is a model, r/k selection theory would predict that k-selective humans are more aggressive than r-selective humans. There are counterexamples either way, and so r/k selection theory should be treated as a way of categorizing reproductive strategies. There is the multiplicitous, slutty rabbit way, and there is the high-investment, 1950’s kangaroo way. That is the best way to approach r/k selection theory for humans.
This model matters for politics, because humans have a moral duty to pursue k-selection. R-selection is a shameful practice that defines the human underclass. Political theorists need to acknowledge the biological underpinnings of these status differences by understanding r/k selection theory and how each strategy can succeed over the other.