THE CANNIBAL'S PUZZLE

While exploring the jungle three scientists get caught by a tribe of cannibals. Begging for mercy, they finally are granted one last chance to save their lifes: Each of them is bound to a stake, so that one scientist can see the backs of the other two before him, the one in the middle can only see the back of the one in front, while the latter can't see anybody. They are now shown five colored feathers, among which there are three white ones and two black ones. They are then blindfolded and each of them is put one of the feathers into his hair. Finally they are taken off the blindfolds and posed the question to determine the color of their own feathers. If only one of them should be able to guess the correct color, all three of them would be released.
Time passes... then the man bound to the foremost stake (who actually can't see anybody) correctly names the color of his own feather. What thoughts must have lead to his answer?