Many comic book characters are recognizable by their costumes and still many are recognizable even just by looking at their silhouettes. Wolverine, however, is in the rather unique situation where he is recognizable by his skeleton! Yes, if you strip away all of the excess flesh, muscle and tissue, Wolverine's skeleton is still so distinct that he is easily identifiable.
What's interesting, though, is that for as popular and as famous as Wolverine's adamantium skeleton is, there are still a lot of things that are a bit of a mystery about how it all works. For instance, it's been over 40 years and we still don't know for sure who was behind Wolverine getting the adamantium skeleton in the first place! It had been around for almost two decades before someone said, "Hey, how does this actually work with his bones breathing?" And, of course, it wasn't until 1993 that we got to see what Wolverine would be like without the famous skeleton, and boy, were we in for a shock when we saw what he was like without the adamantium. Here, we will try to fill you in on as much of the history of Wolverine's adamantium skeleton as we can.
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20WAS WOLVERINE BEHIND WEAPON X?

For years, there was not even an actual mystery over where Wolverine received his adamantium skeleton. He worked for the government, they called him Weapon X, it was pretty much implied that the government gave him the metal. He never acted like it was a mystery. Then, sometime in the mid-1980s, he revealed that he did not actually remember anything that happened to him before he showed up at the home of James and Heather Hudson.
That led to Barry Windsor Smith writing the storyline "Weapon X" in the pages of Marvel Comics Presents, where he showed how a government project kidnapped Wolverine and experimented on him, giving him his adamantium skeleton. The story, though, left it a mystery as to who was actually behind the project. It was later revealed that it was this mysterious clawed mutant known as Romulus. Romulus, though, shocked the world when he said that he was told to do the project by Wolverine himself! That has since been forgotten about, so it is unlikely that it is still part of continuity. It seems like it would be a rather major deal if Wolverine had been the person behind the Weapon X project!

19THE SKELETON WAS ORIGINALLY SOLID ADAMANTIUM

It is fascinating to see the various ways that ideas in comic books are developed as times passes by. Something that made sense when it was first introduced might soon turn out to be based on iffy reasoning, and people had to come back in and alter things to make them work out. A notable example of this is when the writers on X-Men revealed that Cyclops could only open his visor by clicking on a button on the side of his visor. The problem there, of course, was that numerous artists over the years had drawn Cyclops opening his visor without touching his visor at all. So it was revealed that Cyclops also had a button on his glove that he imperceptibly pushes on other occasions.
Similarly, when Wolverine's adamantium skeleton was introduced, the idea was that he literally had a skeleton made out of adamantium. That fact lasted for a while until people started to wonder, "Wait, how could that possibly work? Wouldn't that mess with all of the traditional functions of bones?" So it was then revealed that his skeleton was instead coated with adamantium instead of just being made out of adamantium (even that changed over time, as well).

18WAS APOCALYPSE REALLY BEHIND IT ALL?

The interesting thing about Windsor-Smith's original "Weapon X" story is that he specifically wrote in a mysterious boss who was in contact with the scientists working on the Weapon X project. He did this because he did not want to mess with Chris Claremont's original plan for who was going to be behind Wolverine's adamantium. Claremont had come around on the idea of using Apocalypse to be the one who gave Wolverine the adamantium, considering that Apocalypse had done a similar experiment on Angel, turning him into Archangel. When Wolverine and Archangel first met, Wolverine smelled something familiar about him that drove him insane.
Moreover, in the classic graphic novel, Wolverine: The Jungle Adventure, by Walter Simonson and Mike Mignola, Wolverine traveled to the Savage Land, where he ended up fighting Apocalypse in a secret lab that Apocalypse had there that he was using to experiment on natives of the Savage Land. Wolverine freed them and killed Apocalypse. It turned out, though, that "Apocalypse" was actually a robot made to look like Apocalypse and the real Apocalypse had manipulated Wolverine into eliminating his malfunctioning robot. While at the lab, though, Wolverine discovered an adamantium skull and it really made him think.

17LADY DEATHSTRIKE'S PROBLEM

Another issue with adamantium is the question of how could Wolverine have been given an adamantium skeleton in the past if we saw the issue of Avengers where Adamantium was invented and it was fairly recent, certainly not set years earlier than when Wolverine made his debut. That, in turn, led to a reveal that it was actually a Japanese scientist who came up with the idea for adamantium bonding, likely unrelated to the metallurgy experiment which resulted in the creation of Captain America's shield. The experiment that adamantium was ultimately based on, you see, was an attempt to replicate Cap's shield.