Yesterday's octopus story brought it back to mind. When does a change in degree become a change in substance? That is, when does enhanced tool use change into, to coin a word, cyborgisation?
For that is surely what we're undergoing if you accept the logic of this argument:
Technically, you're already a cyborg. If you keep your cell phone with you most of the time, especially if the earpiece is in place, I think we can call that arrangement an exobrain. Don't protest that your cellphone isn't part of your body just because you can leave it in your other pants. If a cyborg can remove its digital eye and leave it on a shelf as a surveillance device, and I think we all agree that it can, then your cellphone qualifies as part of your body. In fact, one of the benefits of being a cyborg is that you can remove and upgrade parts easily. So don't give me that "It's not attached to me" argument. You're already a cyborg. Deal with it.
To think we may already have almost imperceptibly started morphing. Such ideas provide the thrill of science fiction - and yet we're living them. Possibly.