Periodicity Emerges from Evolved Energy-Efficient and Long-Range Brachiation

This paper examines the emergence of periodic motion as consequence of evolutionary pressure for energy-efficient partially-passive dynamic brachiation. Brachiation was simulated for gibbon-like creatures in a realistic physics environment. The morphologies of the brachiators were identical to each other and consisted of a simple 3-bodied system two arms and a torso. Brachiator performance was controlled by their genome, which contained their initial position at t=0 and torque functions which were applied to the shoulder for t>0. Performance for each brachiator was measured by total distance traveled and energy-efficiency of locomotion. Brachiators found in the first two Pareto-optimum curves were selected for reproduction. It was found that energy-efficient long-range motion resulted in periodic motion in the brachiators.