tas8831

The green nerve is a different nerve - the Superior Laryngeal Nerve. I don't know if the argument is that the Recurrent Laryngeal Nerve is "bad design" necessarily, rather it is an example of inefficient or weird 'design.' It is easy to understand as an artifact of embryological development, and as a 'leftover' of evolution, a retained developmental pathway. So basically, early in development, the region that become the larynx is 'right below' the developing brain and skull. The Vagus Nerve travels from the brain to the thorax and abdomen, and the RLN is a branch off of this. And during this early development, that branch goes pretty much straight to the larynx. However, when doing so, it goes below a blood vessel, which will become the aortic arch. The developing heart and in this case, the aorta, is much closer to the area we think of as the throat at this time, so that makes sense. However, as embryological development continues, the heart, and its attached blood vessels (like the developing aortic arch), moves down into the thorax. But the RLN is still 'below' the aortic arch, so it gets 'dragged down' into the thorax as well. Now in humans, this is an oddity but not a huge deal, I suppose. But consider the giraffe....