Well, as far as I know, there are still many proven cannibal-cases known from the near past as well as present, when in severe survival stresses, like after a plane crash into the nowhere, or a japanese regiment on a northern island, who lost contacts and where separated and could only survive by eating some of them (Something similar is known about the Japanese, having eaten Chinese in China during the war etc.), when out of contact with the rest of their folks. But some members obviously also kind of offered themselves, when realising, that they could not make it anyhow. There were according films, plus reliable background informations about real facts and interviews from survivers, but I can't remember their names.
Apart from this, yes, an important amount of the Christ mythology dates back to mediterranean ritual cannibalistic activities, very well proven, but I do not have the sources at hand, yet they are very well known in historican circles hereabout,
For example in Jordania and around, as well as on some mediterranean islands, I think, also Malta and Sardinia for pretty sur.
It dates back to an old moon cult. The cycle was of importance, since you for example have the three days "dead", plus resurrection after, already clearly included.
They expected the moon to be eaten and reborn. Thus, the oldest son often was sacrificed on an altar (the places are still there, and they found human children bones on all places) and eaten by the priests. While the following born one, after the ritual, was supposed to be the very same one, a reappearance of the one, who was eaten, and thus honored accordingly.
This was later replaced by a lamb, and is the reason, why many believe, that the Isaac (the bush and the ram) story represents the change of that habit, been shown another sacifical object than just the son.
But the later lamb-idea is still connected with eastern, for example, and the basics in the last meal ceremony before christ's (sacrifical for believers) death is clearly also related to this old habit, including the resurrection after three days. Eastern (and the lamb!) still is related to moon cycles, not sun, by the way, although now to the fullmoon.
You can be sure, that in that region, the old local rituals were still known to priests.
Since there are similar stories in old egypt, also related to the moon's disapearance and resurrection, some get it confused with solar myths as well. If they also practiced cannibalism, I do not know, but could also be, since it was all interconnected.
Ritual human heart eatings on the american continent thus were later even.
However, it simply shows, that it was an accepted practice in small, thus maybe before this, even in large. I would not be surprised.
You may also like to read this page:
Cannibalism - Wikipedia
(oops. . .)