Spare Parts

At what point do you stop being you?

There’s an old joke that goes “I’ve had this axe for fifty years. Of course, the handle’s been replaced three times and the head twice.” It’s humorous because obviously that’s not the same axe anymore in terms of having any of the original components that it was built with. But it’s not entirely a joke, in that you can easily picture somebody feeling that they’d always had “that axe” even though they’d had to replace parts of it over a long period of ownership. And at what point did it stop being the same axe? When you replaced the first part? When you replaced the second part? Would it matter if Head 2 and Handle 1 had been together longer than Head 1 and Handle 1?

These questions become pertinent as we approach an era of replaceable human parts. We can now transplant hearts, lungs, livers, kidneys, eyes (or parts thereof), bone marrow and, of course, blood. In the near future, it’s becoming clear that stem cells will be key to growing all manner of replacement parts, from teeth to brain and nervous system cells.

I’m all in favor of this technology, but I do think it raises some questions about the human condition. It forces us to think about the nature of humanity in ways we’ve never really had to before. What is it that makes us human, and how much of our body can I replace and still be me?

The first question might be, what makes me me in the first place? From the inside, it’s indefinable, I’m just me. I’m a conscious, sentient person and as long as I remain self-aware, I’m me. But as a society, we find it necessary to be able to tell one person from another reliably. People aren’t inherently interchangeable with each other, so from a socio-economic and legal standpoint, it’s vital to be able to distinguish one from another. But how do we really do that?

By facial appearance? Heck, a little acid can fix that, and face transplants are now a reality (though both leave the individual badly disfigured at this point).

By fingerprints? Oops, were those your hands in that wood chipper? Sorry!

By retinas? We know that it’s all fun and games until somebody loses an eye. Or two. Besides, I think it’s still up in the air as to whether a stem-cell-grown eyeball will manifest the same retinal pattern or not.

By dental records? If we can grow new teeth from a stem cell bud in just a few months, how reliable are those going to be?

By DNA? This one’s actually pretty good, but if you’re monozygotic twins (something like .2% of the human population), it can’t identify which twin you are, just that you’re one of them. “You’re one of the Jackson twins.” Oh yeah? Well am I the rich-CEO-twin or the alcoholic-bum-living-on-the-street twin?

By knowledge? Each of us typically knows stuff that nobody else could possibly know. But if nobody else knows it, how easy will this be to use to conclusively identify somebody?

At this point, we’re still far short of consciousness transference – moving one mind into a different body – but nearly every other marker can be destroyed or invalidated in some fashion already. Passing yourself off as somebody else is still a challenge, particularly a particular person, but becoming “not me” is manageable. And once we can grow spare parts, it becomes far less debilitating. And make no mistake, there will be a black or grey market for these sorts of parts and services (as there already is in certain transplantable body parts today) once the technology makes them available – regardless of the laws and ethical dilemmas in place. If you can grow me a new me, and I can afford it, hell yes I’ll take that 6-month-old part to replace my decrepit 70-year-old original. But if replacing my hands or my face or my eyes makes it impossible to validate that I’m still me, or makes it easier for criminals to escape justice, then society will need to come up with a new definition of what makes a person a person. Or an axe an axe.