rationalskepticism.org

The nerve has two branches, left and right. In humans one is longer than the other as it is 'entangled' with the aorta. As we reach adulthood this branch gets longer and longer. In the giraffe it seems clear that evolution of the neck, to feed and fight, has made this detour dramatic.
What Dawkins is saying is - if you wanted to design a creature from scratch one wouldn't create a huge and seemingly unnecessary loop of costly nerve fibre, fibre that should go from the brain and into the larynx (it does not feedback information from the heart).