Consider these two phenomena in the ocean environment:
Imagine yourself as a blue whale roaming over the deep ocean. Your sensory perception is well adapted for listening to very low frequency sounds, and attending to sound patterns and reverberations (ambient noise as well as other whales) over long periods of time. You are also acutely atuned to water temperature gradients and pressures. You eat small zooplanktonic organisms; millions is a single mouthful, tons in a single day.
Describe what the two phenomena in the ocean environment events would sound like (images and metaphors might be useful here). How could you sense them? Can you figure out a way to predict when and where your next feast might occur? Does listening to the sounds of the ocean for finding food pre-adapt you for acoustic communication or navigation? Something else? What might the whales' descendents be like in another million years?
In the ocean, sound is the most effective modality for communicating and sensing one's environment. All marine vertebrates studied to date are known to perceive and produce sound. The sub-order of marine mammals known as the mysticetes, or baleen whales, evolved from a common terrestrial ancestor some 25-30 million years ago. Existing evidence shows that whales have well developed inner ears and proportionately large auditory areas in the central nervous system. Species that primarily inhabit shallow, coastal waters are considered most ancestral, while those that roam the deep ocean are more derived. There are obvious differences between the types and characteristics of sounds produced by the coastal and pelagic species. Interestingly, there are also major differences between shallow and deep water environments, especially in terms of how well sound propagates through the water and features of the ambient noise. Thus, for example, coastal species such as bowhead, right, and humpback whales all produce a great variety of complex sounds over a wide range of frequencies. Bowheads and humpbacks also sing complex songs that undergo constant improvisation, indicative of cultural learning. In contrast pelagic species, such as blue and fin whales, produce very loud infrasonic sounds and their songs are relatively simple patterns of infrasonic notes that very little variability.
Certain fundamental features of the whales' calls and songs are very well adapted for long-range communication. All this so far fits within a fairly classic case in which long-range signaling behaviors are adapted to the physical environment. However, I propose to go beyond this basic explanation by sharing several insights synthesized from a suite of experiences studying whales. These insights are derived by realizing that the acoustic experiences available in the marine environment are not as simple as they might appear. To start with, sound fields generated either by one's own voice, the voices of other whales, or the natural ambient environment (e.g., waves, rain, wind) and their interactions with the hard and soft components of the ocean create opportunities for sensory exploitation. Reflections are constantly everywhere. This raises the possibility that over the course of evolution, whales have evolved mechanisms to acoustically map their environment by exploiting such phenomena as long-range reverberations (echoes) and modal excitations of the water column. One conclusion from such considerations is that these animals have cognitive maps of large portions of the ocean world, long duration acoustic memories, and are mentally adept at processing perceptive reflections. If one's perceptions, memory and one's sense of position in a three dimensional world are primarily acoustic (i.e., you don't close you eyes and envision memories of food, landscapes or mates you close your ears and audition memories of food, ocean scapes and, mates), and highly evolved for dealing with acoustic reflections, how might this influence one's sense of being?
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