Natural selection is an astoundingly creative phenomenon, molding species to fit their environments, even if that means turning their faces into shovels. It's also created a galaxy of ways for animals to move about, from walking to crawling to flying. Nature does know what it's doing, and roboticists are more than happy to steal evolution's ideas. The result is a plethora of curious and clever machines that are beginning to traipse and hop all over the place.

Which is not to say you'd want to precisely copy the way an animal moves. (Good luck to whoever tries to replicate every bone and tendon and muscle in a snake's body.) Instead, researchers simply take inspiration from the natural world and run with their imaginations. Researchers at Carnegie Mellon, for example, have developed a snake robot made of 16 decidedly unbiological actuators, or motors, that move in concert to mimic the way a real serpent would.

Sure, being made of metal means the robot isn't as pliable as a fleshy organism. "But it also means that there's going to be things that this robot can do that a biological snake can't," says CMU roboticist Matt Travers. The thing can constrict around your leg like a real snake, but can then twirl its motors to move up and down your limb--more rolling than slithering. Robots that mimic biology are both limited in what they can do with metal and plastic, but also gifted in their own way.

As roboticists look to nature, they can sometimes prove--albeit accidentally--just how efficient evolution's creations are. Take Cassie the bipedal robot. It looks like a pair of disembodied ostrich legs not because its creators at Agility Robotics set out to mirror that form. Engineers did the math to get the most efficient locomotion they could, and landed on a form that just so happens to look avian.