These reports are simply variants of a very old thing, but mostly relating to blondes, and they've been quite debunked so far. I'm sure much of the same reasoning also applies to red hair.
And the slightly less mind numbing version on Snopes.
All these articles online say that National Geographic says so. I can't find any such article in NG. Get back to me when they actually do.
There will always be redheads!
I'll do my part!
Anyone wanna help? >.>