Meeting Abstract
Some animals contact the substrate on which they move using simple appendages — limbs with few degrees of freedom, which interact with the substrate with what is effectively a single rigid contact, such as a horse’s hoof. Other animals have large multi-fingered feet, prehensile tails, or multi-segment tarsi. Why do some locomotor appendages have many mechanical degrees of freedom while others have only a few?
From first principles of Newtonian mechanics, it can be seen that when animals need to produce distinct and unanticipated mechanical configurations (“symbols”) so rapidly that environmental noise becomes a challenge, this produces a lower bound on the number of degrees of freedom needed in the body.
In particular, if an animal needs to emit N different symbols, the animal’s energy budget for emitting each symbol must be at least order of 2N times the energy of typical environmental noise — otherwise simple bodies cannot work. As this safety margin approaches 1, the number of degrees of freedom needed in the locomotor appendages quickly rises to infinity.
