Jon Krakauer, the reporter responsible for the bestselling survival stories Into Thin Air about a Mt. Everest climbing disaster as well as the harrowing tale of Chris McCandless’ flight from civilization in Into The Wild, which was turned into a major motion picture by Sean Penn in 2007, has made a discovery surrounding the death of McCandless. A highly emotional tale, the story elicited a variety of responses from viewers and readers, some finding McCandless to be a woefully immature and unprepared young man who made a rash decision that ended his life, while others imagined themselves in his shoes and admired McCandless’ radical decision to leave society behind in favor of a less wasteful lifestyle.

In a personal blog entry written for New Yorker Online, Krakauer reopened his investigation into the conditions surrounding McCandless’ death. Krakauer had initially speculated in the 1996 first edition that McCandless poisoned himself by accident through wild potato seeds (Hedysarum alpinum). Based on unsubstantiated speculation, the alkaloid poisons that Krakauer believed killed McCandless didn’t exist: the literature, both popular and scientific related to the plant suggested that its seeds were non-toxic.

Since then, Krakauer received thousands of letters that speculated their own theories about McCandless’ death. Regardless of peoples’ personal opinions, for 20 years nobody has managed to accurately assess the conditions surrounding McCandless starving in the Alaskan wilderness, until very recently.

A second theory Krakauer floated involved McCandless accidentally eating wild sweet pea seeds (which actually are toxic) instead of wild potato seeds, but Krakauer ruled that theory out when he noted that McCandless had extensively researched a field guide on edible plants, called “Tanaina Plantlore / Dena’ina K’et’una: An Ethnobotany of the Dena’ina Indians of Southcentral Alaska” in which the similarity between wild potatoes and sweet peas is thoroughly explained.

With McCandless’ death still unexplained, Krakauer stumbled upon an article written for a website collecting essays reflecting on the life of Chris McCandless. “The Silent Fire: ODAP and the Death of Christopher McCandless,” written by a bookbinder named Ronald Hamilton from the Indiana University of Pennsylvania Library, postulated that a common legume containing an amino acid called ODAP was responsible for McCandless’ failing strength all those years ago. Neither a chemist or botonist, how did Hamilton discover this amino acid that scientists supposedly missed for 20 years?

Hamilton had read about a WWII-era concentration camp called Vapniarca, where Nazis had fed the legume Lathyrus sativus to its male prisoners in the form of bread. Krakauer says that Lathyrus sativus has been known to be toxic since Hippocrates was practicing medicine, and that the conditions described in Hamilton’s report on the concentration camp mimic the conditions McCandless lived under since fleeing civilization. If young men eating poor diets and working strenuous conditions find themselves with an excess of ODAP in their system, they find themselves battling paralysis and extreme weakness. The description seems to match the account McCandless wrote in his journal mere weeks before he died: “EXTREMELY WEAK. FAULT OF POT[ATO] SEED. MUCH TROUBLE JUST TO STAND UP. STARVING. GREAT JEOPARDY.”

Hamilton wrote that “[ODAP] affects different people, different sexes, and even different age groups in different ways. It even affects people within those age groups differently …. The one constant about ODAP poisoning, however, very simply put, is this: those who will be hit the hardest are always young men between the ages of 15 and 25 and who are essentially starving or ingesting very limited calories, who have been engaged in heavy physical activity, and who suffer trace-element shortages from meager, unvaried diets.”

At that moment, Krakauer felt certain that they had found their answer, and he decided to return to the scene of McCandless’ death and collect wild potato seeds for lab analysis. When the analysis came back, the seeds McCandless collected to subsist upon were discovered to contain .394 percent ODAP, which the laboratory reports was more than enough to cause the weakness. And so it was that Christopher McCandless died not of caloric deficiency, but of paralysis brought on by ODAP toxicity.

Read Krakauer’s full article here; it’s a fascinating read.

[Image via a YouTube video about a hiker exploring the trail to the bus where McCandless died in the Alaskan wilderness]