Howling:The Tenth Planet - part of a negated timeline?

I've been wondering recently if the class series story "The Tenth Planet" might actually take place in an earlier version of history that's since been negated. It's set in 1986, but the technology is far too advanced for our 1986 - There is something called International Space Command, and Earth possesses Z-bombs, which are said to be powerful enough to split the planet apart. Obviously, these things don't exist as of the present day in the Whoniverse, otherwise the goverment would probably have used a Z-bomb rather than plain nuclear warheads in the Osterhagen Project in "The Stolen Earth/Journey's End." The thing is though, if the timestream of that story was negated, what happened in the subsequent version of history when Mondas came to Earth? Even if the Cybermen were still defeated, it would not occur in the same way, and much of subsequent Cybermen history would be effected. If we assume that the timeline in the episode is negated, what could have negated it? Of course, if anyone can come up with explanations as to how it could still fit in current Whoniverse history, I'll be very interested in reading them. 82.2.136.93 08:16, August 2, 2011 (UTC)