Most Mammals Are Colorblind orThe Evolution of Color Vision

Our color vision is based on three different types of visual pigments. This is called trichromacy and as a matter of fact, it is quite unusual in the animal kingdom.

The following information is a compilation of the article Color Vision: How Our Eyes Reflect Primate Evolution.

Animals have either only one visual pigment, like a few nocturnal mammals. Or they are dichromats, which means they have two different pigment types. This is true for almost all mammals—except the primates, which are most often trichromats. And some birds, fish and reptiles even have four different types which makes them sensitive also for ultraviolet light sources.

The questions arises now: How comes that we are trichromats?

1st step: It looks like that the short-wavelength (S) pigments are the most ancient ones, as they are found in almost all vertebrates.

2nd step: Similar forms to our medium- (M) and long-wavelength (L) pigments are also found quite often—and therefore very old. But only a few primates have both of them, so this has to be a recent evolution.

3rd step: Let’s say the M pigment existed (we actually don’t know). And then through some mutation of a few acids in the DNA the L pigment evolved. Now a first interesting step happened: Some female primates inherited one X chromosome encoding the M pigment and one X chromosome the L pigment and they became thrichromats! This way only female primates could be trichromats as only they have two X chromosomes (male = XY).

4th step: Now the New World primates evolved away from Old World primates. They still are carrying the information encoding color vision as described above. But in the lineage of Old World primates a next interesting development happened: A female primate merged the M and L encoding into one single X chromosome through mutation! This way also male primates became trichromats (thanks!).

5th step: This genetic mutation had such a strong advantage (seeing more colors = finding more good food) that X chromosomes encoding only one pigment were wiped out of the genetic pool.

This five steps of the evolution of color vision sound very interesting. But there are also some questions which arise when reading through, which make me think that we didn’t get to the bottom of it yet. Here are my questions:

  1. How comes that our ancestors suddenly could see the new colors only because of a new pigment type?
  2. Can really only one female primate be the source of our trichromatic vision?
  3. And why the hack are there still so many color blind people? Why is color vision deficiency in so many forms still that widespread?

The authors of Color Vision: How Our Eyes Reflect Primate Evolution have some answers ready. But I’m not sure if I can believe what they are writing.

And there is still no answer for my most important question. Maybe you have one? — Why is color blindness still such a common disease?

Color Blindness in Transportation

Brian Chandler—a red-green colorblind Traffic Engineer from Missouri—just started a new web site to discuss colorblindness and its effect on transportation. He named it Grey Means Go and gathered already some very nice examples.

Grey Means Go by Brian Chandler

If you tell somebody about your color blindness they often ask, if you have a driver license (“I’ll better watch out when you’re on the road :-)”). This is actually handled very differently in each country. For example in Romania you are not allowed to drive if you have any form of color blindness (visit Discromat by Vasile Tomoiaga to learn more about this).

Are colorblind drivers a danger to society?

Some say yes, others say no. Brian has at least some ideas, how to enhance certain aspects in transportation to help not only the drivers which are suffering from color blindness. Have a closer look at the following examples from Grey Means Go:

  • Reflective and even retroreflective backplates of traffic light signals help to identify the correct position of the light at night.
  • Yellow tail lamps increase the vehicle visibility and reduce reaction time in a significant way. But would this also be true for colorblind drivers?
  • Shaped signal heads which definitely are a great aid for colorblind drivers.

I’m looking forward to read more about this very interesting topic and I hope that also many other traffic engineers will take this issue more seriously.

WoW Improves Accessibility for Colorblind Gamers

If you are colorblind it can be sometimes quite hard to play certain games. Something as simple as a green team playing against a red one can be a big issue if you have a color vision deficiency.

World of Warcraft is one of the most played games around the world. Blizzard, the company behind the game, will introduce with the next patch (3.1) a module for disabled people. This includes a part for enhancing the interface for colorblind people. Some objects, which were traditionally color coded, can now be assigned to letters or symbols.

The people from AbleGamers, a community for disabled gamers, interviewed a lead developer from Blizzard, Tom Chilton. They wanted to learn more about this new colorblind option.

Here is a list of enhancements for colorblind WoW gamers. The listed features either support an already existing color coding or replace it.

  • Tags distinguish friendly, neutral, or hostile creatures and enemies.
  • Gear quality has additional text descriptions.
  • The three different coin types are labeled with single letters.
  • Recommended character level is listed as a number.
  • Learned recipes will be rated from + through to +++.

This sounds like quite a big step forward. As a colorblind less than part time gamer I am very happy about every little enhancement in the games I play. Almost never I can see the difference between color coded stuff in the first moment. So I either will learn it during the gameplay or just never really know what I am doing.

In the case of such a big game like World of Warcraft, there are obviously many more possibilities to enhance it for gamers suffering from color blindness. Here is one more example, taken from the same article:

Additionally, some things were overlooked in Blizzard’s version of this add-on. Rogues accumulate combo points as they attack their victims. These combo points are shown as red dots in an arc around the picture of the rogue’s target. As the points are accumulated, the red dots are filled in.

Someone who was colorblind to the color red would not be able to tell the difference between a red dot filled in with red and a red dot lightly shaded with red. One member of the player base identified this problem and created a specific add-on called Kast Combo Points that would change the way the points are displayed. This modification changed the red dots so that they are completely hidden until a combo point is awarded.

Dear colorblind gamer, I’m sure you will and already found your personal way to play the games you like. And if color blindness gets to much into your way, just play another game. Don’t forget, it’s just a game.