[mapt]

Some of the arguments would imply that we should only really have the one ear, since you can do it all with complex spectrum shaping.

But binaural gives us a dramatically easier grasp of left-right localization. For a lot of things, that's all you need!

But the animal kingdom is large and diverse, and high-fidelity up-down-left-right localization would be similarly valuable in numerous places. It is a little bizarre to me that there's no freaky bat or something out there that evolved an extra molar into its own little secondary sonar sensor, with a centimeter of baseline from the normal set. Because with robotic sensors it wouldn't even be a question what to do.