Derrick gasped as the rough fabric of the loincloth started ot heat up. His groin felt tingly. Grok stood there, staring, with a big smile of his hairy face. Derrick blushed as he began to get hard. His cock was soon at full mast, his normal 5 inches. Just then the feeling got more intense. Derrick's crotch was throbbing.
Derrick saw his erection getting longer and longer, stretching the fabric even more. It felt like someone was pulling his penis, stretching it out longer and longer. He could feel his balls getting bigger and bigger, too. Within seconds, the loin clothe ripped open. Derrick gasped as a huge thick hose of a cock spilled out. It was around a foot long. It didn't resemble his old cock at all, or a human cock for that matter. It was criss crossed in a network of thick veins, and the skin on his cock was now dark and very leathery. Hair had erupted everywhere! He couldn't even see his balls his jungle like bush was so thick. He reached into the hair and found his balls. He found them to be much bigger, around the size of tennis balls. He sniffed his hands and gagged; his crotch reeked! It smelled like BO and stale sweat! Gross!
Just then, Grok reached over and grasped Derrick's cock. He started roughly stroking. Within seconds, Derrick blew his load. At first, it was pearl white, but after a couple shots, it turned into thick, chunky, yellow neanderthal cum. It was so sticky and smelly! He shot load after load after load of the new cum. Finally, his orgasm subsided, and his huge cave cock became soft. It slowly drooled precum and cum all over the floor.
"There. You now have caveman cock. Just first step", Grok grunted out. Derrick couldn't believe what had just happened. His cock was now a caveman's cock! Hairy, huge, and stinky! His balls were massive now, churning out thick, inhuman cum! And Grok says that is only the first step! Is he going to turn me fully into a caveman?!
Derrick glanced down and saw a few brown hairs sprouting in between his small pecs. This unnerved Derrick as he had never had any chest hair before. What was happening?!