"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 Rose. "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."
Rose looked down at herself and felt her 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 Rose's normally-smooth skin. And she was no longer taller than before. As they got close to a minute, the changes got more obvious. She developed body hair all over, and she had lost about 4 inches in height. At the same time, her body got thicker, and her features coarser.
Kevin and Jeff watched in awe. It was still Rose, but the changes were dramatic enough that she looked like some brutish relative. About a minute and a half in, there was a sudden and more drastic change. Rose's face shifted to a more simian look, and her skull seemed to get lower, but extend back further, an unibrow forming above her eyes. Jeff nodded.
Rose looked in awe at her now devolved body, a lot more muscular and harier than usual, but still sexy in her opinion. "Me like new cavewoman look", grunting to herself as new instincts permeates her primitive mind.
Sending a lustful glare at Jeff and Kevin, the now neanderthal Rose decides to...