This account simply won’t work: we have never observed what Churchland gives us as explanation. And it is not even very good explanation, focussed too narrowly on cooperation, etc…
The question of human morality is another one of those Hard Problems, like that of consciousness, and scientists should simply confess their ignorance here.
Churchland argues that, deep in our evolutionary history, our early biological systems for self-preservation evolved to promote concern for others, as natural selection favored mammals that could better care for their offspring.
From here, she goes on to explain how basic biological systems—such as our brain’s systems for pain, pleasure, and learning—have interacted with more recent biological developments, such as neurochemicals like oxytocin, to expand our circle of concern beyond the self. Caring for kin and kith, for instance, induces feelings of pleasure and reward, making us more likely to value others’ well-being.
Churchland explains that the capacity to care for others allowed for trust, cooperation, and other kind, helpful (or “pro-social”) acts. In some cases, these benefits gave an evolutionary advantage to those who developed enhanced social skills, like recognizing other’s psychological states and solving social conflicts. Churchland suggests that the ability to understand and consider others’ desires or needs—empathy—is a prerequisite to morality and lies at the heart of moral reasoning.