Are we witnessing the next step in human evolution?

If you were trying to describe a rainbow to a person that cant see, what would you say? Your response would probably essentially be: "It is a ribbon of the colors red, orange, yellow, green, blue, indigo, and violet.

 We are able to see these colors because the average human retina is trichromatic, it contains three color-detecting cones: Red, Blue, and Green.

From these three cones, roughly 100 gradients of color can be picked up by the the human eye and these gradients are then translated by our brain into a million different hues.

Now even though we can describe a rainbow to someone that can't see it, it may be difficult for them to imagine those colors if they have never seen them.

That is exactly how we would feel if we posed the same question to a tetrachromat.
What is a tetrachomat? It is an individual that has an extra cone that lies somewhere in between the red and green cone, essentially an orange cone. This extra cone allows these individuals to have "super" vision--they can see an additional million hues. The rainbow a tertachromat will see has colors within colors.  Is this the next evolutionary state for human vision?

Maybe for a few. The majority of genes that dictate vision are on the X-chromosome and tetrachromatic vision is thought to arrive through a gamate that contains two green cone gene. Ironically, this type of x-chromosome comes from a parent that has at least one x-chromosome that causes the recessive disease of color blindness.

So a child with super color vision arises from color blind parent (unless x-inactivation is taking place). Wow, I am not sure if this is natures way of playing a joke....you just have to love genetics!!


References/Future Reading:
http://ghr.nlm.nih.gov/condition/color-vision-deficiency
http://nexthumanproject.com/references/Tetrachromats.pdf
http://www.post-gazette.com/news/health/2006/09/13/Some-women-may-see-100-million-colors-thanks-to-their-genes/stories/200609130255