The economy of the shape of limbed animals

A simple, high-level wire-minimization model appears to drive the relationship between animal limb number and body-to-limb proportion in some animals across at least seven phyla: annelids, arthropods, cnidarians, echinoderms, molluscs, tardigrades and vertebrates. Given an animal's body-to-limb proportion, the model enables one to estimate the animal's number of limbs, and vice versa. Informally, the model states that a limbed animal's large-scale morphology is set so as to maximize its number of limbs subject to the constraint that there is not a more economical shape which reaches out to the same places. A consequence of animals conforming to the model is that their large-scale morphology is "minimally wired." Just as wire minimization is important in artificial information processing devices, it is hypothesized that one reason why animals' large-scale morphologies conform to a save-wire principle is to minimize the system-wide information processing times.