http://www.adn.com/2007/10/08/219344/theories-differ-on-the-cause-of.html
Did 24-year-old Christopher McCandless inadvertently poison himself when he died in an abandoned bus in the Denali wilderness 15 years ago?
In his best-selling book "Into the Wild," author Jon Krakauer argues that McCandless did -- upon eating the seeds of Hedysarum alpinum, a historically edible plant commonly known as wild potato (also "Eskimo potato").
Collecting some near the area where he died, Krakauer sent the seeds to the University of Alaska Fairbanks chemistry department for testing.
At first, lab testing appeared positive for poison. But a more extensive analysis the next year -- examining additional seeds that UAF graduate student Ed Treadwell harvested near Fairbanks -- prompted department of chemistry chairman Tom Clausen to conclude that the seeds weren't poisonous after all.
"There were no toxins," Clausen said in a recent telephone interview. "And we looked at everything -- roots, seeds, stems and leaves."
End of theory, right? Not yet. When movie director Sean Penn's film version of "Into the Wild" reaches Alaska this month, viewers will see a variation of Krakauer's theory. In it, McCandless confuses wild sweet pea -- which local guidebooks have long listed as poisonous -- with wild potato.
(Krakauer was aware of that possibility, but he dismissed it in his book after concluding that McCandless probably knew the difference between the two plants -- since he'd been eating wild potato roots for weeks.)
As Alaska wildflower expert Verna Pratt points out, however, the wild potato and the wild sweet pea are much harder to tell apart once they lose their blooms in midsummer.
The leaves look almost identical unless you examine them from below, Pratt says. The underside of the wild potato leaf has small veins on it; the underside of the sweet pea leaf doesn't.
"It's not difficult to confuse them if you're not familiar," says Pratt, the author of "Field Guide to Alaskan Wildflowers." "He could have made a mistake."
So is the poisoning theory in the movie a better bet than the poisoning theory in the book?
Not necessarily, says Clausen, the UAF chemistry professor. Because when he and Treadwell tested the wild potato seeds, they also tested wild sweet pea seeds harvested near Fairbanks -- and determined that they didn't contain any alkaloids either. Neither did their roots, nor their leaves.
Then why do guidebooks, like "Wild, Edible and Poisonous Plants of Alaska," published by the University of Alaska Fairbanks Cooperative Extension Service, call wild sweet pea poisonous?
The sole evidence the book cites is the anecdotal experience of a 19th century party of Arctic explorers led by Sir John Richardson who reported getting sick when they ate wild sweet pea that they thought was wild potato.
Clausen questions why no one else has gotten sick from wild sweet pea since then, and he thinks Richardson's men may have been poisoned by something else.
So is the poisoning theory in the movie as unlikely as the poisoning theory in the book?
Not necessarily, says Pratt, who notes that plants in the pea family do have a demonstrated tendency to absorb selenium from the soil. (Selenium is a trace element that's essential to livestock and humans in small amounts, but can be highly toxic in large amounts, resulting in a condition veterinarians call "blind staggers.") The Western states are notorious for selenium-saturated soils. How much occurs in Alaska, however, isn't readily known.
Still, location matters when you test the toxicity of flora, Pratt says. A plant that isn't poisonous in one spot can easily be poisonous in another -- if the soil it's growing in is saturated with something toxic.
Maybe so, Clausen said. But he hasn't seen any evidence yet that the plants McCandless ate are poisonous -- either from the book or the movie.
"And at some point," he said, "you have to let your hypothesis go."