The Riddle of The Sphinx

In Greek mythology, the Sphinx was a creature with the body of a lion and the head of a human or sometimes a ram or a falcon. It was said to guard the entrance to the city of thieves and would ask travelers a riddle. The riddle was what walks on four legs in the morning, two legs in the afternoon and three legs in the evening. The answer was a human who crawls on four legs as a baby, walks on two legs as an adult and uses a cane as an elder.