I had a random thought today: why haven’t wheels evolved in nature? They’re so straightforwardly useful, hence their ubiquity in human-designed mechanical devices, and yet they don’t seem to have emerged in nature – despite billions of years of evolution and lots of other highly complex things emerging through that process.
As ever, Wikipedia pulled through. (What a brilliant human achievement it is.) It’s probable that the wheel is unlikely to emerge through evolution because it’s only useful in its full form, rather than its intermediate forms; you’d have to reach it in one fell swoop, rather than gradually. As Richard Dawkins notes in Climbing Mount Improbable:
“The wheel may be one of those cases where the engineering solution can be seen in plain view, yet be unattainable in evolution because it lies [on] the other side of a deep valley, cutting unbridgeably across the massif of Mount Improbable.”