At first glance, Cassie sure looks like a copycat. Or should we say copybird? Designers used a lot of the Creator’s ideas when they engineered the leggy robot. They experimented with the angles and lengths found in bird limbs.

But motors are not muscles. Rods are not bones. And computer chips are not brains. A robot will never be able to match the incredible complexity of God’s creatures. And anyway, if engineers were really setting out to create a copybird, they didn’t get very far.

Take a close look at Cassie’s legs. You can see gray rods that connect to electric motors. The motors push and pull on the rods to move Cassie’s limbs and feet. Push? Whether it is bird legs, tiger paws, monkey arms, or your big toes, muscles never push. Your body has more than 600 muscles, and every one of them only pulls.

Your muscles work in pairs. The bicep muscle is a flexor. When it flexes, it bends the elbow. The tricep muscle is an extensor. When it tightens, it straightens the arm.

In some ways, Cassie is like a bird. The muscles that move a bird’s long legs are up close to the animal’s body. Bird muscles pull on long tendons that stretch over joints and attach to bones. When muscles flex, they pull the tendons to move the bird’s legs and feet. God’s design gives bird legs a loooong range of motion with a short pull of a muscle. Cassie’s designers used that idea.

You can see how this works with a few simple materials: a long strip of cardboard, string, duct tape, and a table or counter. String and tape the cardboard as shown. Then tug the string from above. Watch how the cardboard “leg” swings a long way with a short tug.