The Doctor, the Old Man, and the Boy Scout

A Famous Doctor, an Old Man and a Boy Scout were on an airplane with engine failure. Unfortunately, there were only two parachutes. 

The quick thinking Doctor stated "I am the smartest man here", so he jumped out! 

The Old Man said "My time has been good and the end is near so go on kid." 

The Boy scout replied "No that is okay, The Doctor who was the smartest man here was in such a hurry, he just jumped out with my knapsack."