"We should go one at a time, just to be safe. It would be bad if we all devolved too far and then couldn't get back." He nodded to Kevin. "Let's start with you first."
After some discussion, the three teens decided to strip down to their underwear so the most body would show. Jeff set the Chronivac up and aimed the camera. "OK. I'm going devolve you until you are something like a Neanderthal. When we get that far back, I'll stop and we'll see how you feel." He started the camera. "Here we go."
Kevin grinned and slipped off his underwear just before Jeff started the Chronivac. "Might as well get the whole picture."
Rose chuckled. "Don't worry. You won't scare anyone with that thing."
"Wait until I'm a huge honkin' cave man!" Kevin looked down at himself and felt his face. "Doesn't seem much different."
Jeff watched the screen. "We're going back about 100 years a second. You do look a little hairier, and shorter." It was true - some light body hair had started to appear on Kevin's normally-smooth skin. And he was no longer taller than Rose. As they got close to a minute, the changes got more obvious. He developed body hair all over, and he had lost about 4 inches in height. At the same time, his body got thicker, and his features coarser.
Rose and Jeff watched in awe. It was still Kevin, but the changes were dramatic enough hat he looked like some brutish relative. About a minute and a half in, there was a sudden and more drastic change. Kevin's face shifted to a more simian look, and his skull seemed to get lower, but extend back further. Jeff nodded. "He's going Neanderthal, I think."
Kevin stared at himself, feeling his arms and chest, grunting in what sounded like approval. They stared as he settled into a smaller and thicker, hairier version that seemed to match most illustrations of Neanderthals. It was so fascinating to watch, that another shift started before Jeff thought to turn off the Chronivac. Kevin got smaller, and his skull shrank down to something more like a chimpanzee's. He was very hairy now, almost ape-like, and was no longer recognizable as ever having been human.
Rose stared at the primitive creature, who was still staring at itself and now feeling its genitals. It grunted and clicked to itself. "I think he's way back before even Neanderthals! Homo Erectus! Like two million years ago!"