Vision

People with red-green color blindness can see green camouflage in finer detail. Less distracted by color, they rely on brightness and texture, making concealment easier to spot. Wartime accounts say Allied forces used colorblind soldiers as photo interpreters.

Humans are the only primate with obvious white sclera. Apes have darker sclera that hide gaze direction, but human eyes broadcast where someone is looking. The Cooperative Eye Hypothesis says this 'eye that cannot lie' helped early coordination and group hunting.

An Ostrich eye is about 5 cm across and 60 g — heavier than its brain. The eyes occupy more skull space than the brain, flattening it between them. This visual system helps spot predators from up to 2 km away: an evolutionary trade-off for a flightless bird.

Claude Monet's 1923 cataract surgery removed his right eye's lens, giving him a rare ability: seeing ultraviolet light, which healthy lenses filter out. Water lily flowers glow in UV. His late paintings show it — strikingly more blue and violet than anything before the surgery.

Pirates may have worn eye patches for more than just injuries. Since they had to fight while quickly moving between the bright deck and the dark below, they may have used eye patches to keep one eye pre-adapted to darkness.

Humans see three colors; the mantis shrimp sees 16. Most mammals see only two, having lost color receptors during the dinosaur era as nocturnal creatures. Primates alone regained a third through a mutation that helped spot ripe fruit among leaves.

Before World War II, British RAF scientists couldn't crack bomber interception. Commander Grenfell guided fighters by eye, hitting 90% accuracy with the 'gaze heuristic.' This principle later inspired the American Sidewinder missile.

A baseball outfielder does not calculate where a fly ball will land. They simply run while keeping their line of sight to the ball at a constant angle. Falcons hunting ducks use the same method. This instinctive tracking is called the gaze heuristic.