I remember reading, it may be apocryphal, that Stan Lee created the idea of a "mutant origin" in comic books because he was tired of coming up with individual origins for each and every superhero he created. Regardless of the truth of this statement, in the past forty years the Marvel universe has seen a significant population increase in its mutant minority. Whole nations in the marvelverse are populated with them, or at least they were.
According to ICV2, and you already have a sense of this if you have been reading House of M, there will be a 95% reduction in the mutant population in the Marvel universe. To "non-fans" that might seem drastic, it might even seem like something that would upset this "curmudgeony" comic collector. Well it is drastic, but it isn't particularly upsetting.
One of the most compelling elements of early mutant stories was that they paralleled the civil rights struggle. Mutants were a persecuted minority. X-men like Cyclops and Jean Grey were hated for their "freak powers," while Iron Man and Thor were adored for theirs. At first, that might seem absurd. Both sets of individuals have powers (okay Iron Man has technology technically, but you get the point) so why aren't they feared equally? When I was younger it didn't make any sense at all. It wasn't until I really thought about the X-men/Civil Rights parallel that it became clearer. Sure I had always "known" what the undertones of the X-stories were, but I hadn't asked the same "why" about our own society. Why would people be hated just because of the color of their skin, their gender, religion, you name it? That didn't make sense either. So why do people hate the X-men and not Power Pack? Because they do, and they do so without reasons. Are there evil mutants? Sure, but Rhino isn't a mutant and he is powerful and evil so why not hate all superheroes?
This compelling element had been diluted in recent years by the explosion of characters. No longer were mutants a persecuted minority, they had become a persecuted "seeming" majority. The pathos was lost in the commonality, but all that is about to change.
Joe Quesada, the Editor in Chief at Marvel has been adamant that "As long as [he] am EIC [he is] not bringing any of these (characters) back." He also "pointed out that the effects of the 95% reduction in the number of mutants in the Marvel Universe would be reflected through the line -- Wolverine will be the only mutant in The New Avengers."
Addressing the curmudgeon in me Quesada stated, "The idea behind House of M and Decimation is to scale back the number and role of mutants in the current Marvel Universe to something similar to the Silver Age Marvel Universe."