Humans have relied tremendously on radio-frequency communications for exchanging information. But nature seems to rely on chemicals, light, acoustics and so on for communication between members of the same species. Are there any examples of radio-frequency communications by organisms other than ourselves? If not, what is the physical basis for this exclusion?
鈥� Given the ubiquity of cell membranes with controllable one-way resistance, living organisms probably could develop radio reception, but it would be more difficult to develop mechanisms to radiate strong signals. Natural selection is not teleological; it selects only for immediate benefits in fitness, so it is hard to see how true radio signalling could develop in nature. Conversely, artificial selection and genetic engineering are highly teleological, so there might be no theoretical obstacle to other organisms developing radio communications through the use of such tools, though it would be a long-term project.
Still, there is one class of sensory and communication organs that could perhaps be classed as radio or ELF (extremely low frequency). Various species of fish use pulsed or oscillating electric fields at frequencies of up to a few kilohertz, depending on the species and the type of sense organ. Many species hunt using passive reception, but some actively generate fields for navigation, communication and hunting. Such fish are so varied they form a field of study in their own right, and the function of much of their field modulation is not understood but, for example, if the signal frequencies of two fish interfere, they will shift frequencies to accommodate each other鈥檚 transmissions.
Advertisement
鈥淟iving organisms probably could develop radio reception, but it would be more difficult to develop mechanisms to radiate strong signals鈥�
Jon Richfield, Somerset West, South Africa
鈥� One reason animals do not communicate over radio is that there has never been any need to communicate over such long distances. I guess the expense and energy needed to evolve something like a radio transmitter/receiver would not be justified by the benefit over chemical signalling.
鈥淪hort-distance communication and more permanent forms of signalling, such as scent marking, have proved more useful during evolution.鈥�
Short-distance communication and more permanent forms of signalling, such as scent marking, have proved more useful during evolution. It is more important to know 鈥渨ho is or was here鈥� rather than 鈥渨here is everybody?鈥�. Marking your territory with long-lasting chemicals is evolutionarily cheaper than sustaining a radio beacon.
Jan Strojil, Olomouc, Czech Republic
鈥� I think that asking the question differently would help to shed light on the subject. Why would an animal want to use radio waves to communicate?
Radio waves and light waves have different wavelengths. Visible light wavelengths are in the region of 400 to 700 nanometres. That happens to be a good size for cells to detect. Radio waves, which run a wide spectrum from AM radio frequencies to TV signals to FM and more, are much larger. Even short-wave radio wavelengths range from 13 to 60 metres.
Long wavelengths are great for humans to use in communications systems because they can travel long distances without interfering with things in their way. But they are no use to an animal. How would it detect the waves? In any case, animals generally don鈥檛 need to communicate over long distances, and when they do they can use acoustic methods, for example, which are perfectly good enough. Over short distances, visible light is much easier for biological organisms to detect, and it uses systems already in place.
David Taub, Karlstad, Sweden