Any estimate is just that, an estimate. However ...
A study published at
http://faculty.plattsburgh.edu/thomas.wolosz/introtoevolution.htm
offers some details about probability and the passing down of eye
color.
In order to use this research, we must make some assumptions:
1) Assume that the entire world population has either brown or blue
eyes. I know this is not true, but bear with me for now.
2) Assume that even in societies where brown eyes are incredibly
dominant (ie. Africa, the Orient), there is always a chance that blue
eyes will pop up once in a while.
3) Assume that despite the dominance of brown-eye genes, some
societies (ie. Scandinavia) will produce more blue-eyed people than
science can account for.
Assuming a normally distributed population, roughly three-fourths
would have brown eyes at any given point in time. According to the
U.S. Census Burea ( http://www.census.gov/ipc/www/worldpop.html ),
there are about 6.2 billion people in the world now.
Let's eliminate all those odd folks out there with green or gray eyes
by lowering the population sample to 6 billion.
The best (and admittedly very rough) estimate I can come up with is
that 4.5 billion people have brown eyes, or about 73% of the world's
population.
Search terms:
"brown eyes" world percentage |
