Genetic & maybe "melanin" & maybe where they living?
Phenylketonuria or overload with something like Aspartame & maybe alcohol mixed.
Can't remember if got it right, but I know phen & melanin are on correct side. The hole picture of this:- They is one missing on the left & one missing after dopamine. I think I will try and find the image again.
http://www.bupa.co.uk/individuals/healt ... lketonuria
Too much breaks this
Phenylalanine / / tyrosine
tyrosine side attached
melanin / dopamine
[img][800:473]http://www.willroberts.com/pku/block.gif[/img]
_________________
INTJ, Type5 Observer, Ecologists,
?When you make a mistake, don't look back at it long. Take the reason of the thing into your mind and then look forward. Mistakes are lessons of wisdom. The past cannot be changed. The future is yet in your power.?