I don't think there is a natural warrant for it. It seems natural to us, but it is a cultural standard, ultimately grounded in Christian ethical theory. — Wayfarer
It is natural behaviour in the sense that the group benefits from all its members having equal opportunity. That maximises the group's degrees of freedom. All individuals start on the same level when it comes to being able to pursue the group's goals and so the role of historical contingencies - such as a family history of poverty or wealth - is minimised.
In other words, social democracy and its call for level playing fields makes obvious good sense even in an economic growth situation. It maximises the group potential for creativity and adaptivity.
So the rationale for Christian social behaviour is quite naturalistic - the reason it endures. It is only the claimed ontological basis that appeals to supernatural forces. And who believes in God anymore? (Not Anglicans.)
However the trick that organised religion pulled was to convince enough people that there were beliefs and powers that transcended their existing social structure. There was one God who ruled over all kings and tyrants. So getting people to act in the name of rational abstractions required religion as a stepping stone.
So yes. You can say Christian moral philosophy identified the smart way to organise human societies once they started building cities and building up trading networks. But that came out of an identification of rational social principles, not because of what God had to say about "Christian feelings".
Right - there's the rub. Humans are differentiated by 'existential dread' - which is precisely a consequence of self-awareness and the sense of separateness from nature that humans have but that animals do not. Much of what goes under the name 'philosophy' comes from the contemplation of the source of that dread - 'who am I? What is the meaning of it all?' But then, you say, that it is something that can by understood in evolutionist terms. See the sleight of hand there? — Wayfarer
Well first let's dispose of the OP. And accepting that sentience has these sharp discontinuties as well as its underlying continuities is the start of beginning a sensible conversation on "specieism".
If you now want to discuss something else - morality as the wise habits of social organisation - then what I would say about existential dread is that sensible folk accept life for what it is and get on with making the most of it in rational fashion.
If you find yourself stuck in a loop asking "who am I?", you are not listening to the natural philosophy that says you are primarily an actor within a community. There isn't really "a you" that is distinct from the pattern of relations that is your social engagements. So "you" have the best hope of finding "yourself" by looking outwards to the world you are helping to co-create rather than inwards in search of some mysterious essence - a soul or will or anything else so disconnected from reality.
What I'm saying is that your pragmatic naturalism is very good - as far as it goes. But it doesn't serve as the basis for a moral code. Given a moral code, a pragmatic approach may well be best, but that code can't necessarily be derived from or justified on the basis of naturalism. — Wayfarer
Again, as I always have to keep saying, my naturalism is constraints-based. So it already says that we will only find broad limits shaping our personal actions. Thus morality is about constructing a hierarchy of constraint that runs from the broad and inescapable necessities (we need food, shelter, etc) to the very personal (I must get rich, get smart, get contented, etc).
So the point is to be able to fix the biological constraints at the correct distance from the other constraints, such as the cultural or the personal. I have never said biology ought to dictate anything. I only say it sets the scene in a basic way. And we need to understand what "it" wants of us if we are going to be able to fix those constraints at the right distance in terms of living our lives.
This hierarchically organised approach is in sharp contrast of course to regular moral thinking which wants to tie our actions to overly concrete abstractions. Things are good and bad in a black and white fashion. But a constraints-based approach is naturalistic because it only ever talks about fostering propensities to "do the right thing" and so tolerates exceptions, either accidental or deliberate, to a reasonable degree.
This is an evolutionary logic - and one that places positive value on individual competitiveness or local degrees of freedom. So I can choose to be vegan, or a Nazi, as my personal moral choice. On a small scale, as a local experiment, it is not particular immoral in terms of even cultural norms, let alone the much more distant naturalism of our biological history. It is only as veganism or Nazism becomes an organising idea - a constraint - at a larger social or biological scale that it starts to be judged by the forces of natural selection.
So if you are going to go the natural philosophy route, it is much more Pragmatic in this fashion. It is all about constructing an appropriately organised landscape across which our behaviour adapts. Like an onion, we have to be able to place biology at its best distance from our moment to moment decision making.