Re: It's possible to exist men who have one eye in the middle of the forehead?

Back in my teaching days, I used to have a great slide that I would use for 
my embryology classes.  I got it from the front page of The Star, a tabloid 
newspaper.  The caption for the photograph was "Doctors Stunned by Birth of 
One-Eyed Baby", and the picture was a mostly normal-looking baby with his 
eyes airbrushed out of the photograph and a totally fake looking picture of 
an eye pasted to his forehead.  It was always good for a laugh.

This condition does exist in real life in both animals (as you have seen) 
and humans, and it is called cyclopia.  Real-life examples don't look 
anything like they do in the comics or sci-fi movies - check out the link 
for some examples - 
www.seatopia.com/miscellania.html [Not for the squeamish - Moderator].

Cyclopia in humans and animals is probably the most severe manifestation of 
holoprosencephaly, which is a defect in brain development in the early 
embryo.  In mild cases of holoprosencephaly, brain development is nearly 
normal and there are few or no obvious facial deformities.  In cases severe 
enough to cause cyclopia, the brain is so defective that the baby is either 
stillborn or dies soon after birth.

The causes of cyclopia and holoprosencephaly are mainly unknown, although 
clues are being discovered.  There are studies indicating that part of the 
cause may be a defect in how the embryo uses cholesterol during development.  
A gene that may be involved in holoprosencephaly has also been identified - 
it's called, believe it or not, Sonic hedgehog (yes, after the video game 
character - it was discovered originally by fruit fly geneticists and they 
often have a strange sense of humor).  Here's another link to an article 
describing some of this research - http://www.niehs.nih.gov/centers/1998news/ctrnews9.htm