They almost made it. They reached the slopes of the Sierra Nevada mountains in early November, but then the weather turned with a vengeance. One of the harshest winters ever recorded arrived early, as Michael Wallis, author of the book The Best Land Under Heaven: The Donner Party in the Age of Manifest Destiny, told NPR. The area was blanketed with foot upon foot of snow. Their supplies and herds had already been decimated during the previous weeks of struggle. They were snowbound; before long, they were starving. They really did eat everything else first — oxen, then their hides; leather; bones cooked and re-cooked. They were left with each other. It’s unclear who might have been deliberately murdered in order to provide meat for the survivors; it’s certain that two Native Americans were shot and butchered.

In a February 2017 interview in Smithsonian, Bill Schutt, author of Cannibalism: A Perfectly Natural History, said, “We have these sets of rules we try to follow. But when the going gets tough, that stuff eventually goes out the window… . There’s a biological directive to survive and at that point, when you reach that extreme, you’re not worried about the fact that there’s a taboo. You simply want to live.”

Rescue parties finally reached them in March 1847. Of the 81 trapped by the snow, 45 walked out alive. Roughly half had engaged in cannibalism. Only two of the original dozen families made it to California without suffering a death.