Are humans unique in being able to see things in colour

asks homer

A. A few animals, including humans and the other primates, fish, amphibians, and some birds can see colour. But only a small group of primates, including humans, can see the full range of colours, from reds to greens. The others' colour vision is restricted to blues and yellows.

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Q. How did humans and some other primates evolve full colour vision

A. New research suggests that this advanced form of colour vision, known as trichromatic vision because it involves three colours, gave our ancestors a survival advantage as it allowed them to select the most nutritious food.

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Q. How does red-green vision help with food selection

A.�Peter Lucas and Nathaniel Dominy of the University of Hong Kong, China, studied the eating habits of primates in the Kibale National Park, Uganda, to see how their ability to see colours influenced the leaves they ate. They found that the chimpanzees and monkeys able to see the full red-green colour spectrum selected the tasty young red leaves among the green trees in the Tropics.

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Q. Why are young red leaves better to eat than older green ones

A. They are easier to digest and have a higher protein content.

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Q. But some humans do suffer colour blindness, why

A. In some ethnic groups, notably Caucasians, up to 8% of males have red-green colour blindness, a condition virtually none existent among the group of non-human primates that have red-green vision. Because more humans suffer from colour blindness that monkeys, we may be loosing our ability to distinguish red and green, perhaps because it is no longer essential for us to do so.�

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by Lisa Cardy