At One Time The U.S. Military Used What To Spot Heavily Camouflaged Enemies?
Answer: Colorblind Men
Camouflage relies heavily on blending an object into the surrounding area both by mimicking the color and the patterns found around the object. Any skill at detecting problems in the coloration or pattern give the observer an immediate advantage in locating camouflaged prey or enemies.
To that end, the U.S. Army discovered that colorblind men were excellent at detecting camouflaged enemy equipment and installations because their brains were more inclined to examine and match patterns (since color data wasn’t as reliable or accurate for them). When shown photos of locations with hidden enemies and their equipment, they were able to find them faster and more consistently than their non-colorblind counterparts.
Colorblindness affects roughly 8% of men versus 0.5% of females. Evolutionary biologists have argued that the ability to see camouflaged prey and hunt it more easily must have served men well enough for it to be preserved as a trait in a larger percentage of the male population.
Image courtesy of Wikipedia.