I like Steven Pinker but he's wrong.
All knowledge begins with the senses. So, imagine our long-ago ancestors in a time before language was invented. Since they couldn't see, hear, taste or smell the difference between right and wrong, isn't it likely that they felt it?
Isn't it likely that they intuitively felt the guidance of conscience, warning them of wrongness, long before they could speak or write and use reasoning to write stupid moral rules like "Thou shalt not kill?"
And even dumber, our laws on killing are failed, useless reasoned attempts to write an absolute rule covering future situations of almost infinite variety when an unbiased jury given all the relevant facts could rely on conscience to make the right call.
When criminal laws result in judgments that agree with the judgments of conscience, they are coincidentally right the way a stopped clock can be right twice a day. When the law conflicts with the judgments of conscience, and the law prevails, injustice happens.
I'm far more inclined to your view than Pinker's (given the rather obvious pitfalls of trying to derive moral behaviour from what is 'rational') as I think it has stronger merit and empirical backing, but I still think its rather teleological, almost mystical thinking - if taken to the same extreme as the "
cult of reason" approach.
Environmental factors, and I guess 'epigenetics', are as important in moral development - arguably more so - than appeals to 'reason' or 'conscience', which seem to rest upon a sense of 'enlightenment' or 'moral purpose'.
This line of thought makes a judgment about human 'nature' - what it is to be human, that we are inherently moral beings on the basis of objective standards of good and evil that just 'emerge' in our minds by natural mechanism, like a spark of the divine. I'm not sure that squares with Darwinian science. I actually think its a secular attempt at retaining a theological understanding of human morality, if applied in an absolute sense.
Our moral norms are heavily shaped by environment (both material factors & other people) and socialisation, just as much as they are by empathy and intuition (which provides the basis for identifying our needs and wants and desires and sense of self-consciousness in other moral agents i.e. people, and thus being able - without thinking - to just spontaneously put ourselves in another mind's shoes, based purely on intuition, without consciously thinking it through). And reasoned judgments then play a part as well, albeit in an ancillary function.
Nature and nurture both condition our behaviour.