Sure…
Let me give you an example here:
My hair growth is EXACTLY the same as my father’s. My posture is also the same. It is unbelievable how much we look a like.
My father is of Mediterranean descent, so more hairy
My dad (and my uncle) warned me as a young teen not to shave against the direction of hair growth on your face as the blade will also catch the small vellus hairs and you will have more hairs.
Stubburn as I was, I shaved a part of the face against the hair direction because this way it was easier to get all the hairs there…Guess what, I got patchy hair growth at the EXACT spots where I had shaved against the direction of the hairs for a while…Up to this day I have dense hair growth there and nowhere else.
After I stopped shaving against the direction of the hair growth my face hair growth became stable.
Then, also as a teen, I was swimming with my dad. I noticed the hairs on his abdomen. He said “I was so stupid to shave down there and after every shave thicker and longer hairs started to grow”
I only have a hair line between the belly button and pubic hair. He had exactly the same hair growth but now his whole abdomen are full of hair. So I listened to him and didn’t touch it ever…Up to this day I do not have any hair growth there…
Maybe science has only tested on full European caucasian people…I don’t know but I am convinced shaving does have an effect in some people.
I am a scientist myself, a PhD in Neuro-Psychology. I know the importance of empirically based research and proof. But I do not blind myself by stating that science is absolute.
In the case of hair, I think we people do not know enough and I really think that hair is not physically dead. I think there is some sort of communication going on between the hair cells and the follicle. At least in some people of some descent, like my father and me…
I am utterly convinced that if I was to shave my earlobes, they would be covered in thick terminal hairs within no time…I don’t know why, but I do know my body has this reaction towards it…
So to get back to the experiment. Sure an 18 year old is fine. Make sure you shave the person at least a couple of weeks and report back what happened…