In the Tangled Bank, I wrote about how life has to evolve within constraints–constraints of physics, development, and history. One of the examples I used was the laryngeal nerve in giraffes. It travels down the giraffe’s neck, takes a U turn, and then heads back up again. It seems ridiculous, but makes sense if you think about how it was laid down in fish without necks, and was then gradually modified–rather than re-engineered outright–as tetrapods grew necks, and then taken to surreal extremes in the long-necked giraffe.
Youtube has an excellent snippet of Richard Dawkins hanging out with an anatomist as she dissects a giraffe’s neck, to show what this remarkable evolutionary legacy really looks like. Warning: it’s bloody, like all dissections. But it’s worth the gore!
(PS: Anybody know what show this came from?)