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We all recognize the regenerative capacities of the countless characters from Marvel and DC, and Wolverine is one the first that comes in my mind when speaking of immortality (or "unkillability"?), after Deadpool and many others.
There is already a thread about Deadpool, and although it is also included in X-Men universe, the logic clearly is not the same for both characters. Furthermore, after the events in many X-Men movies - particularly in X-Men Origins or The Wolverine, which in my country is titled "Wolverine: The Immortal" -, we also perceive much more the immortality or semi-immortality after him being shoot in the head or losing part of his members.
I'm a layman when speaking of Marvel comics, but I'm always very curious when it comes to be a subject matter of immortality. For example, what would happen if Wolverine was vertically cut in half? Two wolverine are generated? At least two brains, in ideal conservation ambient, could develop by themselves?
In the real world something similar can happen with non-differentiated stem cells, but I don't know what logic is used when concerning adamantium and tissue regeneration in Marvel universe. I wonder if there are any references that put this topic in evidence in the comics.