Universal constants

[wehasband]

Hello everyone!

I was getting lonely (again) so I thought I'd try to do something with everyone.
The mechanics of this little game of mine goes starts with this question: Is it possible for human beings to share a common trait/preference/experience or is the adage about rugs true? That we're all spun from different fibers and that there is not single thing that we can share commonly amongst ourselves?

So the game starts with me proposing a universal constant with the next poster responding on why it couldn't apply to all human beings. As soon as the explanation has been done then we move on to the next universal constant. The one who put the proposal can also counter-response if he/she can. The one who makes the most convincing proposal wins! [being vague is also an option and a good tactic]

For example:
Universal constant:
Hair
Response:
Alopecia
Not everyone enjoys a head (or bodyful) of hair. Medical conditions that prevent hair growth exist, ranging from skin disorders to medical treatment such as chemotherapy.

Spoiler: Note

While I encourage answers that exhibit profound understanding of the universe, it also wouldn't be bad to keep it simple. The goal is to have fun and learn stuff.

Universal constant:
Biological parents

 

[Ghost Kitty~]

So... are we working with the assumption that everyone has the universal constant? So clones would work here?

 

[Anayomex]

Since thread is dying it means that samy's clones don't work here.

 

[FinalPyre]

Clones still kind of have biological parents. They are still comprised of the DNA of two persons/animals. Unless the clones are completely synthesized (and no longer clones of anything but themselves), but I somewhat doubt that creating such a being will soon, if ever, be within the capabilities of mankind.