The two on the front nine where added for variety primarily, as there was a run of similarly length two-shooters on the original routing.
Wille Fernie added his short hole "Ailsa" c.1909 (replacing a similarly named two-shooter), which was then shortened by James Braid ahead of the Open in 1923 (now known as "The Postage Stamp")
Braid also added two bunkers on the LHS "The Coffin" and one further forward at the foot of the bank, this stopped the bail-out to the left from where some balls were known to run back down onto the green.
He also lowered a bank at the rear of the green to open up the surface to wind and allowing balls to run through from the rear of the slightly extended green.
The genius of shortening the hole, encouraging a higher ball flight bringing the wind even more into play was evident yesterday, as was the deterent of "The Coffin" as not one player went into this on Day 1 from the tee.
Braid added the new 5th Hole "Greenan" along the coast at the same time.