When do locomotor appendages get complicated?
Society for Integrative and Comparative Biology, vol. 57, pp. E385, 2017
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.
BibTeX
@conference{revzen-2017-sicb,
author = {Revzen, Shai},
title = {When do locomotor appendages get complicated?},
booktitle = {Society for Integrative and Comparative Biology},
year = {2017},
volume = {57},
pages = {E385}
}