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Humans Have Apes to Thank for Colorful World 


By Patricia Reaney

LONDON (Reuters) - Humans have apes and monkeys to thank for their acute 
sense of color, scientists in Hong Kong said on Wednesday.

If our primate ancestors had not needed to distinguish red from green to 
survive -- to find tasty ripe fruit and nutritious leaves in forests -- 
humans may not have evolved with the ability to enjoy such a colorful world.

``We humans owe our unique color vision to our primate ancestors,'' Nathaniel 
Dominy, of the University of Hong Kong, said in an Internet interview.

Apes and monkeys from Africa and Asia can see vivid reds, greens and blues 
just like humans in contrast to all other nonprimate mammals. Dominy and his 
colleague Peter Lucas studied four species of Old World primates in Uganda to 
find out why.

``Our study is the first to link a nutritional value with primate food 
colors,'' said Dominy.

In research reported in the science journal Nature, the scientists monitored 
the eating habits of primates in the Kibale Forest in Uganda to see how their 
ability to see colors influenced which fruits or leaves they ate. 
Distinguishing the healthiest food is essential for primates to survive.

Dominy and Lucas found that apes and monkeys can choose fruit using only 
yellow/blue vision but the animals had to see red and green to find the most 
nutritious young leaves which often have a tinge of red that sets them apart 
from the green forest.

``We found that a primate lacking the ability to discriminate red-green could 
still detect ripe fruits but not red leaves. There is value to this because 
young leaves are rich in protein and easier to chew. All primates, even those 
that eat mostly fruits, have to rely on young leaves during the year when 
fruits are unavailable,'' Dominy explained.

But he added that more humans suffer from color blindness than monkeys so we 
may be losing our ability to distinguish red from green.

Only about three percent of monkeys are red-green color blind compared to 
eight percent of Caucasian males.

``So it looks like the selective pressure on we humans has been relaxed, 
perhaps because we have lived outside the forest for some time now,'' he 
added.