How do we know that nobody 10,000 years ago had blue eyes? Er, well, of course it's impossible to _know_, but what leads us to conclude that nobody 10,000 year

How do we know that nobody 10,000 years ago had blue eyes? Er, well, of course it's impossible to _know_, but what leads us to conclude that nobody 10,000 years ago had blue eyes? Anyone know? Edit: posted this before I saw the other thread and the excellent answer here - http://news.ycombinator.com/item?id=824543 http://news.ycombinator.com/item?id=824543 My mistake.