One of my favorite examples of evolution and how we can see it in living things today: The laryngeal nerve of the giraffe, linking larynx to brain, a few inches away — but because of evolutionary developments, instead dropping from the brain all the way down the neck to the heart, and then back up to the larynx. In giraffes the nerve can be as much as 15 feet long, to make a connection a few inches away. Richard Dawkins explains:
All mammals have the nerve, and as a result of our fishy ancestry, in all mammals, the nerve goes down the neck, through a heart blood vessel loop, and back up. In fish, of course, the distance is shorter — fish have no necks.