The Sontarans, not yet a species of clones, were already, in the Seventh Doctor's words, a "fierce, martial race". They began to sweep over Mutter's Spiral. Only the Rutans opposed them. Reacting to this, the Sontarans stopped reproducing naturally and turned themselves into a clone species. (COMIC: Pureblood) The Rutans and Sontarans both involved themselves in the Millennium War of 150 million years BC. (PROSE: The Quantum Archangel)