Colorblindness

[Asguard]

In the Paleolithic, men were the hunters and women were the gatherers. They had to be able to tell the ripe fruit from the green fruit and the tasty leaves from the poisonous ones. Men went out hunting and the large animals they hunted with spears generally don't bother with camouflage coloration, so they didn't have to figure out what color they were. Maybe that was it.

Alternately, maybe the colorblind gene is on the X chromosome and it's a recessive trait. (Sorry, maybe that info is in here somewhere. I read this whole thread four years ago but I'm not going to do it again.) So the baby will be colorblind if and only if two X chromosomes with the gene double up, and that can only happen in a female.

These are just pure speculation.

Your second part is the correct one, red green colour blindness is caused by a ressssive mutated x which means you need to inherit it from BOTH parents for it to effect a girl but only mum to effect a boy. Blue colourblindness on the other hand (which is much rarer) is not carried on the x and therefore I believe equally effects girls and boys

 

[DavidN]

Every colorblind driver knows that red is on top and green on the bottom.

That I understand; but I have a couple of friends in the severe category who can't see the new LED traffic lights till they are a car length away, unless of course it is yellow.