As you might imagine, the procedure is loaded with ethical concerns. Whether or not you're not averse to animal testing in the first place, the notion of performing a head transplant (especially one where the patient likely won't live long) could easily go beyond the pale -- the Harbin tests probably wouldn't have received funding in the US. There are a number of major technical hurdles to conquer before this is practical for humans, too, such as boosting the number of nerve connections, preventing immune system rejection and keeping the brain healthy in mid-surgery.

The hope, of course, is that all these troubles will pay off. You'd theoretically have a head transplant as a option when replacing limbs and organs just isn't possible. One neurosurgeon, Sergio Canavero, is even vowing to try a human head transplant within two years. The plans are ambitious (and arguably grotesque), but the very fact that they're even on the table shows how much medical technology has changed in recent years.

[Image credit: AP Photo/David Longstreath]