Even Edgar Allan Poe, master of eerie twists and turns, would have been mystified by this mind-boggling coincidence created in part by one of his stories. But let's start from the beginning.
In 1838, Poe's only novel was published - The Narrative of Arthur Gordon Pym of Nantucket. Partway through the book, the crew of a ship called Grampus finds themselves with a busted boat and no food or water. They manage to catch a tortoise and strip off its shell, but eventually, in order to survive, the crew draws straws to figure out which of them will be sacrificed to provide meat for everyone else. The death straw goes to a former mutineer named Richard Parker, who is promptly stabbed to death; his head, hands and feet thrown overboard (you can read the whole grisly thing here). This keeps the floating Donner Party alive a little bit longer, but the two remaining crew members are still on the brink of death when they're finally rescued.
A creative story - Poe actually called it "very silly" - but here comes the real twist. In 1884, a yacht named the Mignonette left England, headed toward Sydney, Australia.
The yacht wasn't really made for trips around the world, so it shouldn't have been a surprise to anyone when it sank in a storm. The four-man crew barely escaped in a lifeboat, but they definitely didn't have enough provisions for survival. They did catch a turtle and eat it, but just like their counterparts in the 45-year-old Poe tale, they needed more if they were going to be found alive when a rescue boat found them.
One man - a 17-year-old named Richard Parker - fell overboard and then made the mistake of drinking seawater to attempt to quench his thirst. Parker started going downhill fast, and that's when his fellow survivors decided they would kill him to ensure their own survival. The men had considered drawing straws, but they figured Parker was so far gone they might as well kill him and drink his blood while it was fresh (instead of risking the contaminated blood that might occur if they just waited for him to die due to illness). After stabbing Parker in the throat with a penknife, the three men devoured him. They were rescued a few days later.
The Mignonette case became quite famous in England. The men went to trial for their crime; two of them were originally sentenced to death. This was later amended to six months in prison. This Monty Python sketch was inspired by the ill-fated yacht and its tragic crew: