Communication via chemical means appears to be the oldest and most widespread mode of signaling among animals. ~ American biologist Kevin Theis et al
Chemistry is the universal language of life. Microbes earn their living as chemists.
In contrast, conscious sense of smell in humans is slight compared to its unconscious perception. Conscious human communication is dominated by sight and sound, with the world becoming tangible via the sense of touch.
For most species, chemo-communication is common, and is a communication channel notably well-developed in insects and mammals. Caste-bound eusocial ants maintain massive colonies using sophisticated communication systems via ~20 different pheromones.
Just as 2 ears and 2 eyes aid perceptiveness in hearing and sight respectively, so too 2 nostrils afford keener olfaction. Locating objects is much easier with stereo inputs, as differential in signal strength determines direction.
Duration is one facet of chemical communication. Some chemical signals are designed to last only a short time. For that, volatile compounds with low molecular weight are employed.
Ant pheromone alarms – to signal others of impending danger – are detectable only within 3–5 meters, and usually fade within a minute or less. If not so, it would be impossible to localize the threat.