Journalist Jon Krakauer, who authored the book Into the Wild (later adapted into a film by Sean Penn and starring Emile Hirsch) about the life and death of vagabond Christopher McCandless, has written a fascinating new article for The New Yorker explaining his new, nearly conclusive determination for the cause of the young man’s death.

If you’ve not read the book, Krakauer hypothesized that McCandless had accidentally ingested the poisonous seeds of wild sweet pea, Hedysarum mackenzii, confusing it for a staple of his diet, the wild potato, Hedysarum alpinum. Though the mistake is easy to make due to their similar appearance, many people have derided McCandless for (among many other things) this final, fatal error. Further, his final note read, “EXTREMELY WEAK. FAULT OF POT[ATO] SEED. MUCH TROUBLE JUST TO STAND UP. STARVING. GREAT JEOPARDY,” indicating that he never realized that he’d even made a mistake (which contradicts the Hollywood ending in the film).

However, Krakauer found an article penned by writer Ronald Hamilton that explains that McCandless most likely did die from eating the seeds of the supposedly nontoxic wild potato, heretofore thought to be safe to eat — even by the very scientists who studied the plant on Krakauer’s behalf:

“I tore that plant apart,” Dr. Clausen explained to Men’s Journal in 2007, after also testing the seeds for non-alkaloid compounds. “There were no toxins. No alkaloids. I’d eat it myself.”

Krakauer relates Hamilton’s findings though, and states that “the toxic agent in Hedysarum alpinum turns out not to be an alkaloid but, rather, an amino acid, and according to Hamilton it was the chief cause of McCandless’s death. His theory validates my conviction that McCandless wasn’t as clueless and incompetent as his detractors have made him out to be.”

The “toxic agent” in question is a neurotoxin, beta-N-oxalyl-L-alpha-beta diaminoproprionic acid, a compound commonly referred to as ODAP. While the wild sweet pea would kill anyone from ingesting due to the alkaloids, it does also contain ODAP — as does the wild potato. And that substance, according to Hamilton, “affects different people, different sexes, and even different age groups in different ways.” He continues:

“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.” [bold added]

Hamilton’s target group essentially describes McCandless perfectly, and the condition he died from is known as “lathyrism,” which kills nerve receptors and causes weakness, difficulty with balance, and ultimately degrees of paralysis and therefore starvation — caused by eating a plant that only now, two decades later, is being realized as having life-threatening qualities. Had he avoided the plant and survived, he would be 45 as of 2013. Instead, he died on August 18, 1992 at the age of 24.

The article provides much more information, including how Hamilton came to gather his knowledge of ODAP poisoning. To read Krakauer’s article, click here, and to read Hamilton’s lengthy essay on the subject, click here.