Rotating locomotion in living systems.
Rotating locomotion in living systems includes both the rolling of entire organisms, and the use of structures that propel by rotating relative to a fixed body, such as a wheel or propeller. Though the former mode is used by varied forms of life, including pangolins and tumbleweeds, the latter is only known to occur in bacteria using microscopic, corkscrew-like flagella. While other human technologies, like wings and lenses, have common natural analogues, multicellular organisms have apparently never evolved rotating propulsive structures. Such structures may be infeasible to grow and maintain with biological processes. Compared with walking or running on limbs, in natural environments, wheeled propulsion is rarely as energy-efficient, versatile, or capable of navigating obstacles. This is likely why at least one historical civilization abandoned wheels. Rolling and wheeled creatures have appeared in speculative fiction and the legends of many cultures.
