Strangely, this made me think about the recurrent laryngeal nerve in giraffes.
The nerve takes a 15-foot detour down the long neck and loops under the aorta near the heart before it travels back up because evolution needed to stay backwards compatible with previous iterations of protogiraffes as environmental selection pressure lengthened the neck.
I love this fact. If you're a fish with no neck, the route it takes is the most direct and obvious. But as evolution gradually lengthened necks the route remained the same!
The nerve takes a 15-foot detour down the long neck and loops under the aorta near the heart before it travels back up because evolution needed to stay backwards compatible with previous iterations of protogiraffes as environmental selection pressure lengthened the neck.