I find it so disturbing and unnerving how, in famines that occurred in the socialist world, some people were in such an extreme situation that they had to resort to eating their own family members and friends. In particular, I heard this occurred during the Great Leap Forward, and the Soviet famines of the 1920s and 1930s.
What caused this to happen?
Cannibalism under extreme scarcity has been a worldwide phenomenon since the dawn of time. Graeber has a chapter on it in debt. Some cultures even had systems where people, usually elderly or disabled people would volunteer themselves. It's pretty depressing but it also shows the sacrifice that people are willing to make to keep their community alive, and would never happen in today's individualised alienated capitalist societies. The alternative is the community dying so from a utilitarian perspective it's an interesting ethical debate. We of course are now well beyond post scarcity, and in the modern day I'd argue for dying while fighting the rich for resources over genociding the elderly and disabled.
They also display this communal behaviour in Snowpiercer, a communist movie/book/tv, where people would sacrifice their limbs for food to keep others alive and the class struggle going.