Johnny Matheny wants you to try something tomorrow: Put on some pants, and a belt—and then shove your dominant hand between your waist and your belt, so it’s strapped in at the wrist. Now brush your teeth, take a shower, make coffee, and do everything else you need to do—with just the other hand.
I tried it. It wasn’t just slow and frustrating, it was damn near impossible. One example: to clean my teeth, I had to open the toothpaste bottle, put it down, pick up the toothbrush, stick it handle-first between my clenched teeth, pick up the bottle again, squeeze some out, put the bottle back down, take the toothbrush out of my mouth, then go at my teeth. It took me 10 minutes.
But Matheny does it every day, at least since his left arm was amputated in 2008 because of cancer. As he told me when we met this past summer, the world is designed for the two-handed. Which is why he’s volunteered himself to be the human guinea pig for the latest and greatest prosthetic experiment currently going on at the Defense Advanced Research Projects Agency (DARPA), the US military’s research wing. He’s gotten a metal socket grafted into his humerus bone and electronic device implants in the nerve bundles of his chest and back, and DARPA has designed and built the most advanced, robotic prosthetic to date specifically with Matheny in mind. (Sadly, his insurance won’t pay for it—it did after all cost millions to develop—so he can only use it during tests at DARPA’s lab.)
Matheny has become one of a handful of modern-day Vasco de Gamas of the human nervous system. Not a decade ago, the best options for those who lost their arms or legs to cancer, infection, enemy fire, or other accidents looked a lot like they did a century ago: rigid, unmoving stumps, maybe with a hook at the end to grasp. But thanks to intrepid patients like Matheny—and innovative neuroscientists, engineers, designers, physical trainers, and surgeons—we’re nearing a time when prosthetic designs will make the leap from rough and clumsy tools to customized, integrated, and elegant replacements that not only obey signals directly from your brain but transmit sensations back to it. The ultimate goal: a replacement limb that can basically do everything important your old one did, without the sunburns and bleeding.