Human nature is triune; it is three distinct natures in one.
1. Unbridled self-interest, "the law of the jungle;" the organism's will to survive and reproduce; culturally suppressed as original sin or an inherently evil nature; long thought a threat to preserving the social order; a zero-sum operator; moral anarchy; politics of plunder; the predator or the parasite; slavery or serfdom of others
2. Unbridled altruism; a social adaptation to enhance the survival of the group at the expense of the individual; culturally reinforced as a duty owed to a superior or as a submission to a supernatural will; lives of the saints; long thought necessary for preserving social order; zero-sum operator; moral community; politics of family and close friends; emotional capital; love
3. Rational self-interest; a social adaptation to enhance both the survival of the group and the life of the individual; recognition of individual rights and property; peaceful competition and cooperation; does not preserve social order; rather, it results in an adaptive social order viewed as chaotic by some and self-serving by others; non-zero operator; moral order; politics of general welfare; symbiosis
A triune nature equips humans to adapt to a wide variety of environments and social structures, but leaves us with a perpetual motive tension that we articulate as competing and at times irreconcilable moral codes.
This is no mere hierararchy of needs. All three natures exist and are operative simultaneously. Each, alone, is a complete operating system for human action, but each is equally complete with the others. Sexual jealousy is no different from professional jealousy.
The paradox of human nature is that it is not additive: one equals three and three equals one.
Human nature is not judged in terms of its content; rather, we judge the content as best we can by its visible results.