Of all the apologies to have to make, surely one of the most awkward must be over the small matter of having eaten someone's great-great-grandfather. This, however, is precisely what the inhabitants of Erromango, part of the South Pacific island state of Vanuatu, are doing.

A hundred and seventy years ago, the distinguished missionary career of the Rev John Williams came to a premature end when he and his companion James Harris stepped ashore on Erromango's Dillon Bay. Unfortunately, recent European visitors had killed some inhabitants, and consequently the newcomers' welcome was violent and brief. When a Royal Navy ship later arrived at the island, as Williams's great-great grandson Charles Milner-Williams explains in this BBC report: "The islanders then said that, yes, they had killed and eaten both Harris and Williams."

Milner-Williams and 16 other relatives have just taken part in a reconciliation ceremony during which the place where their ancestor landed was renamed Williams Bay. A local MP, Ralph Regenvanu, says that many of the (now overwhelmingly Christian) islanders thought that their home may have been placed under a curse because of the killing of Rev Williams and were keen to make reparation. But he also hastened to point out that:

Cannibalism, contrary to what a lot of people think, was traditionally a very ritualistic and sacred practice. It was not something like, you know, have your neighbour for lunch. It was practised in a very ritualistic way and was considered to be a very sacred activity. A lot of the time it was a way of vanquishing a threat, absorbing the power of an enemy. John Williams may have been eaten because he represented this threat, this incursion of European civilisation that was coming into Erromango at that time.

The practice of cannibalism exerts a peculiar horror for us, although, if one accepts the idea of some kind of physical ensoulment, it is not entirely without logic. The philosopher Ted Honderich, for instance, once told me that he was convinced that the Hawaiian islanders ate Captain Cook "because they knew he was a great man". (As Ted's wife, Ingrid, then added sagely: "Yes, you'd fortify yourself greatly by eating someone else.")

Not to make light of this in the least, but apart from societal taboos and various medical reasons, I'm not quite sure what the, say, atheist, utilitarian arguments against cannibalism would be. However repulsive it sounds, I can see why an extreme libertarian might argue that if a body is merely a collection of dead flesh and bones, then why not? Some people do eat placenta (a UK mothers' website even has a page with recipes). Others happily donate their bodies to medical research . . . though any doctor can tell you tales of the mischief students get up to with cadavers: disrespectful is not the word. And as was noted in a trial that received a great deal of attention in 2003, cannibalism is not even against the law in Germany.

None of this is to diminish the importance of the gesture the people of Erromango have made. But I have to say that, given the actions of Europeans carving out their empires with the bible and the sword in the 19th century, I don't blame the islanders for attacking the next white men to land on their shores -- even if putting them in the cooking pot was a bit de trop.

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