Beyond Zero and One (Andrew Smart) / quote 118 of 171
Dragonflies fooled by polarized light
Donald Hoffman relates the following example about dragonflies to illustrate the idea that biological perception does not report the truth about the world: Many dragonflies, for instance, lay their eggs in water. For millions of years, their visual systems have guided them to bodies of water appropriate for oviposition. This is an impressive feat and might suggest that their visual systems have evolved to report the truth about water. Experiments reveal instead that they have evolved a quick and cheap perceptual trick. Water slightly polarizes the light that reflects from it, and dragonfly visual systems have evolved to detect this polarization. Unfortunately for the dragonfly, Homo sapiens have recently discovered uses for crude oil and asphalt, and these substances polarize light to an even greater degree than does water. Dragonflies find pools of oil even more attractive than bodies of water, and end up dying in large numbers. They also are attracted to asphalt roads. Pools of oil and asphalt roads are now ecological traps for these dragonflies. Apparently their visual system evolved a quick trick to find water: Find something that polarizes light, the