Meanwhile, elsewhere tomgpalmer.com: How States Get Started: Darfur, The standard account — horse-riding nomads conquering settled agricultural populations — was written by Franz Oppenheimer and Alexander Rüstow. Woot?! No meeting-in-th…

“I will give this one proof among many from which it may be inferred that all men hold this belief about their customs. When Darius was king, he summoned the Greeks who were with him and asked them for what price they would eat their fathers’ dead bodies. They answered that they wouldn’t do it for any amount of money. Then Darius summoned those Indians who are called Callatiae, who eat their parents, and asked them (the Greeks being present and understanding through interpreters what was said) what would make them willing to burn their fathers at death. The Indians cried aloud, that he should not speak of so horrible an act. So firmly rooted are these beliefs; and it is, I think, rightly said in Pindar’s poem that custom is king of all.”

Now, custom may be king when it comes to how we express certain values (or how much emphasis particular values get), but someone holding out for a general objectivity (or ubiquity) of values would point out that, while each society has its own way of doing it, they are both showing respect for the dead. (Of course, many in each society would think that members of the other society were being disrespectful, but this could be dismissed as a kind of short-sightedness, or a failure of depth of understanding about what the other society’s practice is aiming at.)

I suspect that if one were to take a poll, one would find an overwhelming majority of the population would regard cannibalism as morally wrong, even if it is a question that has not exercised the attention of moral philosophers all that much.

You admit that the tradition of viewing it as “gross” does “anchor a bit towards disapproval,” but I would suggest that this has a lot to do with it, a whole lot. After all, rumor has it that human flesh is actually reasonably tasty, if properly prepared. The distaste is clearly socially induced, and pretty strongly socially induced. I think that a widely held moral judgment, if not adumbrated at length by official (or unofficial) moral philosophers, is very much what lies at the foundation of this distaste.

To paraphrase Mill, the only proof that gets people to adopt a new norm is that they try one and like it. Or, conversely, they find extant norms aren’t worth the trouble. If you like, this is a sort of natural selection: as the social environment changes (in large part thanks to technology), some norms cause more pain or other expense than they bring social utility. Case in point: excessive care for individual life may be maladaptive in a subsistence economy; thus infanticide (or, in extremis, gerontocide — cf. Turnbull’s The Mountain People) may be tolerated. As scarcity decreases, it becomes possible for individual life to become a sacred value: and this may be driven in part by logical considerations such as simple consistency. However, as technology extends the borderlands of life in both directions, people find the existing norm unbearably agonizing or absurd (could every sperm really be sacred?). Ergo, euthanasia and abortion become tolerated. This in turn requires (possibly substantial) revision of existing norms for the sake of coherence. Usw. (Rawls said all this decades ago.)

In this sense, then, there could be moral progress, just as one might regard a behavior or trait maladaptive to a given environment. (Such as, e.g., economists regarding bias as something to be overcome.) If this account is correct, one would expect norms to be partly biological. And they might be.

A last point: Robin said above that our ancestors were likely well aware of empirical evidence that, say, dark-skinned humans were people with inner lives basically the same as Europeans. I have my doubts. Kant, for example, had few if any opportunities to see any non-Europeans at close range. Even within one’s own nationality, it was acceptable practice (not so long ago) for eminent minds such as Gibbon’s to say of the peasant that he was “superior but little to his fellow labourer the ox in the exercise of his mental faculties.” (Remarks not dissimilar to Gibbon’s have appeared from time to time on this blog too, though fortunately not implying such traits are linked to any particular social class.)

In terms of conflicting moral codes, consider the current general
abhorrence of cannibalism. Now, probably pretty much everyone would
agree that it is wrong to eat prisoners of war, which was something
done in many societies. However, the other major form of cannibalism
in “primitive” societies was the ritual eating of relatives after they
died natural deaths. In certain societies this was considered both a
mark of respect for them and for the gods and indeed for the whole natural
order. In his book, Collapse, Diamond reports how back in 1965 he was
working in New Guinea, and his assistant quit to go home to eat a dead
relative (actually, prospective son-in-law) ritually. When told of how
the dead were buried in the West, this man was shocked and denounced the
“waste” and “disrespect” of sticking a relative’s corpse in the ground
to be consumed by maggots.

Can we really say this man was wrong?

I often note that people treat something an act as especially bad if the perpetrator benefits from it (for example “torturing babies for sport” rather than just “torturing babies”). It never made a difference to me whether the perpetrator enjoyed it or not; the victim was the only one that seemed relevant to me. I would guess that most people have that moral intuition because if people do benefit from certain acts they are more likely to commit them, so it is something we are primed to watch out for.