Color blindness is not always a disadvantage, according toUniversity of Calgary primatologist Amanda Melin and her colleagues,who found that wild color-blind capuchins in Costa Rica are better atdetecting camouflaged insects than individuals with broader colorvision.

To determine how color vision affects insect hunting, theresearchers used DNA samples to distinguish capuchins that werepartially color-blind from those with a wider spectrum of color vision.Observations of capuchins foraging for surface-dwelling insects showedthat color-blind capuchins made nearly 20 insect-capture attempts perhour, compared with only about 16 for those with normal color vision.

One possible explanation for the color-blind advantage is that areduction in color signals makes the differences in texture andbrightness more apparent, so it’s easier to see past color camouflage,says Melin.

Could similar effects have caused color blindness to arise andpersist in humans? It’s hard to tell. “Two things could have happened;there may have actually been some advantage for color-blind earlyhumans—they might have been hunting animals with camouflage,” saysMelin. “Or selection pressure for maintaining color vision could haverelaxed because it wasn’t a big advantage in the habitat or types ofhunting used at the time.”