Occasionally,some owe their survival not to struggle,but to simple luck.Take the starting case of Mitsutaka Uchikoshi.One ice-cold October day in 2006,Uchikoshi had been at a party on a mountain in western Japan.After wandering off into a field on his own,Uchikoshi tripped,hit head,and was knocked unconscious.As Uchikoshi remembers,"I was in a field,and I felt very comfortable.That'my last memory."He remained unconscious in almost-freezing temperatures without food or water for more than three weeks.