A billion years in the future, when the sun's increasing brightness has vaporized the oceans and organic life is no more, Iron Thorns rule the Earth. Human dominance was but a brief interval, a strange quirk of history which exploited a particular era's fauna and potential technologies; when conditions changed, the long-dominant Tyranitar body plan resumed its natural place atop the world's hierarchy of species.
Or so it is written, at least, at the end of the Violet Book.
It is easy to understand why humans chose to mechanize a pokemon who had dominated battlefields since the first of their number were tamed, and the early theory that an Iron Thorns rebellion will come to annihilate organic life is no longer taken seriously. Organic life likely died out or mechanized themselves as a means of coping with an inhospitable world, and although it is possible the use in warfare of powerful artificial pokemon such as Iron Thorns made that world inhospitable, natural processes alone, on long enough timescales, are a perfectly viable explanation; to say more would be beyond the scope of this entry.
Futurists and those geologists who deal primarily with space-time distortion rocks refer to the last period of this world's history, one as long-lasting and distant from our own time as the Pre-Cambrian, as the Sideroankathic epoch, after the Greek name for this pokemon. The question of how to avert the Sideroankathic is a difficult one, but popular sentiment and Paldean law strictly forbid anything remotely related to creating Iron Thorns or experimenting on Tyranitar; even electric terastallization is highly illegal. Yet evidence of Iron Thorns continued to appear whenever the space-time continuum was sufficiently disrupted. As of now, we can only conclude that the future refused to change.