Derrick broke into a brisk jog; he had to get to the tree as fast as possible. He felt Drok in the back of his mind, mere moments away from breaking through. Derrick didn't want to end up a smelly, hairy caveman. Derrick, or more accurately, Drok's thick cock was as hard as a steel pipe. The temptation to just stop and jack off was immense. The musky stink wafting up from his hairy pubic bush was making his head swim.
Derrick glanced down and saw his chest was much broader and hairier than it was just a few seconds ago. Derrick had a thick brown rug stretching unbroken from his oversized cock all the way to the base of his neck. Derrick also saw his arms were much longer, with his knuckles hanging down to his knees. His long arms were covered in wiry brown hairs. "Uh Oh. Me change. getting worse.", Derrick grunted to himself.
He looked down at his throbbing erection. He saw pre cum leaking out of the tip of his huge, leathery cock. Derrick grunted and stopped running. The temptation was too great for him. Derrick knew Drok had won. He gripped his erection with his large hand, noticing he now had a great deal of hair on his knuckles. Drok moaned deeply as he began pumping up and down.
The pleasure felt immense as he pleasured him self. Drok was now the dominant part of his mind. Derrick was screaming in his head as he was pushed deeper and deeper into unconsciousness. Derrick was no more. A hairy, smelly caveman by the name of Drok stood there jacking off.
As he pumped his huge neanderthal member, the changes sped up. Drok's body was undergoing thousands and thousands of years of devolution in mere minutes. Drok felt his spine curve and hunch over, forcing his arms to hang lower, very close to the ground, in fact. Drok's forehead bulged out even more as more bone grew on his foreheard, making his thick brow stick out even more. Drok felt a sharp pain in his head as his brain shrunk, becoming smaller and less complex. Drok felt the memories of his old life leave, laving nothing behind but Drok. Even more body hair pushed its way out of Drok's skin, giving him a very thick covering. Drok scratched his armpit with his left hand and he noticed all his pit hair. It was a lot! Just then, a thick, potent BO hit his nostrils. Drok grunted; he really stunk!
With a bestial roar, Drok came spurt after spurt of stinky, yellow caveman cum. His massive hairy balls were being emptied into the grass beneath him. It felt incredible. Drok panted as his orgasm subsided. He let go of his member, which swung and slapped wetly against a hairy thigh. Drok knew he had to get back to his home; the cave room with Grok. He exited the room and made his way back to the lobby. Several guests were visibly disgusted by the new scents his neanderthal body produced, or the sight of a naked hairy caveman. The receptionist pinched her nose as he walked by. "Didn't make it in time", she said under her breath to no one in particular. Drok finlly made it to the cave room and opened the door...