Koban

We colonized over seven hundred planets in 200 years. Humankind enjoyed the benefits of unlimited expansion and the end of wars. We even disbanded our military. Then the Krall found us. The Krall have used thousands of years of combat to select the genes of the strongest and fastest warriors for breeding. They are a species determined to rule the galaxy, through death, destruction, and domination of every opponent. Ruthlessly, they tested captured humans on a savage planet called Koban. The choice faced was simple for the prisoners: Prove humans can produce fighters again, or be exterminated now. The aliens are only part of the captive's problem. Left to die, the captives must survive Koban's high gravity and superfast animals, with organic superconductor nerves. The huge tiger-like rippers are predators too fast even for armed Krall to face. The human solution, with the help of a ship full of captive bio scientists is genetic: If you can't beat them as you are, become more like a ripper. The Krall will discover more than one species can bypass natural selection.