Dr. Kenneth Kamler, a surgeon and adventurer who has explored the Amazon and climbed Mount Everest, said he has seen people survive incredible injuries in some of the most extreme conditions on Earth.
"The human body has this very subtle but extremely powerful ability to squelch pain when you need to have it squelched to survive," he said. "Your brain is directing all its power to get you to survive."
Kamler said that kind of will is an incredibly powerful thing.
"The will to live is paramount in your survival in a desperate situation," he said. "I think it makes all the difference between life and death for many, many people."
Duncan's left leg was amputated at the hip, and the right leg was amputated above the knee. He hopes to soon explore getting prosthetic limbs
Today Duncan has an office job at the rail yard and is an inspiration to everyone who saw him on that June day -- living proof that human beings can beat impossible odds.
"That day," he said, "was a miracle."
To find out what kind of a survivor you are, take the Survivor IQ test.