As you watch you caveman brother explore your room, walking on his feet and knuckles, you wonder how far back you could go. Your brother grunts and spasms, as turn the knob back further. Hair covers his body as he becomes smaller. His face pushes out, and all traces of humanity dissapear.
Your primate brother continues to shrink, and a tail grows from his spine. Your brother was now a monkey.
He crawled over to you, and climbed up on your head. You smile as he picks your hair for insects.
Wanting to go further, you give the knob one good twist. Shaun shudders as his body dwindles in size. His tail became hairless and pointed, as his front teeth became incisers. Shaun was now a small rodent. Shaun should've run like any other prey, but he was still in there... sorta.
Satisfied, you change the year back to the current date and place Shaun on the floor.
As you do, you wonder what kind of dog he'd evolve into.
As soon as you think it, Shaun grows quickly. His form went through another branch as he gained more canine features. His snout pushes out as he becomes a wolf. his fur stared to change to a golden sheen as your bro finished his change into a golden retreiver.
He jumped up, and gave you a big doggy kiss. This was so cool! You could devolve and evolve things, and you could change what branch they evolved along.
Even though this was cool, Shaun was still your brother. you devolved him back to a rodent and sent him on the right branch back to humanity. You watch as his body grows back into an apes. His face draws in and Shaun the caveman stands before you once more.
He grunts and spasms again, as his hair recedes, and his muscles soften. His fore head shrinks back as his face returned to normal.
Shauns eyes were dim and animal like. You see them light up as your brother shakes his head and looks at you.