From The Comics Journal #57 - 1980 Summer Special, John Byrne interviewed by Mitch Itkowitz on the origins of Wolverine:
"It will unless it's changed or we come up with something better. You see, we're already on our second origin for Wolverine. The first origin that was concocted, was that he was actually a mutant Wolverine, boosted up to human form by the High Evolutionary. Okay, that works... except that Archie did a similar number in the first Spider-Woman story. And no matter how things have changed in that strip since, the idea has been done before... so we dropped it.
Unless we change our minds in about a year, we have his origin pretty well worked out now... all sorts of details like where he got his adamantium bones, how he seems to heal so quickly, why he's a lot older than he looks. I don't know if all of those facts are going to come out at once, or in that order. Most of the fans I've talked to--and most of the mail has agreed--say that they like picking up the facts in dribs and drabs.
One of these days, Roger and I have a Captain America story we'd like to do, guest-starring the X-Men, where Cap will be talking to a couple of them, and Wolverine is real quiet at first. And when he finally speaks, Cap will do a take and say, "Corporal Logan?" Because, you see, Cap met him during the war. And that might be the first time we come out in the books and say just how old the guy is. Unless we change our minds. There's a sequence coming up which I hope we will do, where Wolverine will be meeting his father, who is Sabretooth. There will be a big fight and he will kill him on camera, and there will be no doubt about it. This is what Shooter calls a BFD, "Big F*cking Deal." Which I hope will be printed with asterisks, because I don't use that word.
Ho, ho. Gales of laughter. And that will be the one instance where because of the way the story is set up I don't think even Shooter would be able to object to a good guy killing somebody.