While you wait for answers, you might want to check out some previous threads on handshakes:

• When did the handshake become commonplace? - 8 comments, over 2 years old.
• The commenters draw evidence from Antiquity, the Late Middle Ages, and the Early Modern Era.
• What is the History of the Handshake? - 15 comments, over 8 months old.
• Handshakes are traced back to ancient times by one of the commenters.
• How far do handshakes date back? [x-post from r/history] - 7 comments, over 2 years old.
• The commenters in this thread go a bit deeper in the reasoning behind handshakes.