Our vision is limited to a tiny segment of the electromagnetic spectrum, where wave frequencies in their fullness range from gamma radiation at the upper end, downward to the ultralow frequency used in some specialized forms of communication. We see only a tiny bit in the middle of the whole, which we refer to as the “visual spectrum.” Our optical apparatus divides this accessible piece into the fuzzy divisions we call colors. Just beyond blue in frequency is ultraviolet, which insects can see but we cannot. Of the sound frequencies all around us we hear only a few. Bats orient with the echoes of ultrasound, at a frequency too high for our ears, and elephants communicate with grumbling at frequencies too low.
Tropical mormyrid fishes use electric pulses to orient and communicate in opaque murky water, having evolved to high efficiency a sensory modality entirely lacking in humans. Also, unfelt by us is Earth’s magnetic field, which is used by some kinds of migratory birds for orientation. Nor can we see the polarization of sunlight from patches of the sky that honeybees employ on cloudy days to guide them from their hives to flower beds and back.
Our greatest weakness, however, is our pitifully small sense of taste and smell. Over 99 percent of all living species, from microorganisms to animals, rely on chemical senses to find their way through the environment. They have also perfected the capacity to communicate with one another with special chemicals called pheromones. In contrast, human beings, along with monkeys, apes, and birds, are among the rare life forms that are primarily audiovisual, and correspondingly weak in taste and smell.-- E O Wilson
Photo: Alistair Lee
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