Designers of prosthetics and artificial organs have for a long time tried to replicate the human body. From the earliest peg legs to some of the most modern robotic limbs, the prosthetic we make looks like the body part that needs replacing. Lose a hand? Dean Kamen’s DEKA arm, aka the “Luke arm,” is a robotic prosthesis that will let you grasp an egg or open a beer. The Luke arm is a cutting edge piece of technology based on a backward idea – let’s replace the thing that went missing by replicating it with metal and motors. Whether it’s an artificial leg or a glass eye, prostheses often seek to reproduce not only the function of the body part, but the form and feel as well.

There are good reasons to want to reproduce form and feel along with function. The first reason is that our original bits and pieces work quite well. The human body as a whole is a natural marvel, let alone the immense complexity and dexterity of our hands, eyes, hearts, and legs. No need to reinvent the wheel, just replicate the natural model you’ve ...