Shared characteristics in language between ourselves and other species
You are only able to read this paper right now because I communicated it to you through language and you (hopefully) understood. Command of words is a skill thus far known to be unique to humans, and one could argue that the capability of speech is part of what allowed us to thrive as a species. Across the animal kingdom, many organisms have developed systems of vocal communication that, though they may not necessarily constitute a language, nevertheless play an important role in their survival. Birds use song as a means of attracting mates; dolphins have a very sophisticated set of squeaks, chirps, and whistles whose extent and function are currently beyond the domain of human knowledge (Foer 2015). By examining the abilities of various bird species and dolphins to produce and perceive sounds, we can gain insight into the evolution of speech sounds across the tree of life, including where humans fit into this larger picture. In order to communicate vocally, an organism must be able to both produce and perceive sounds. The size and shape of a bird and its beak can have an effect on their sound production, and a comparison of birds’ and human vocal organs can reveal how speech might have evolved in people. Perception of human noises, as well as the way birds and dolphins perceive the noises made within their species may also help gain understanding of which traits exist only in people, and which evolved in some form long ago.
One of the most well known forms of vocal communication is birdsong, and the avians that perform this action are generally considered to include three taxa of songbirds: trochiliformes, psittaciformes, and passeriformes, commonly known as hummingbirds, parrots, and songbirds respectively (Miyamoto 2006). In order to communicate, birds must be able to both produce and perceive sounds. The primary organ that birds use for speech is the syrinx. It is situated in the thoracic cavity between the two bronchial tubes, which lead to the birds lungs; by contrast, humans and most other mammals have a larynx. When a bird vocalizes, membranes on the two bronchi vibrate to produce sound waves as air passes by them. The bird can control these membranes individually in order to create two sounds simultaneously (Attenborough 1998). Additionally, the size and beak shape of birds have also been shown to play a role in the sounds they produce. A bird with a larger body will produce sounds with longer wavelengths; a bird whose beak gapes widely will produce a sound of higher frequency. In closed habitats like the forest or the woods, where sound can be lost to the surroundings, it is advantageous to produce sounds of lower frequency than those produced by birds from open habitats such as the savannah or grasslands (García 2018). Thus, the habitat of a songbird may indirectly affect its body shape.
As birds have incredible control over the sounds they can produce, this skill is used primarily in mating rituals. Although both male and female birds have the mechanisms to produce and perceive song, male birds are the primary performers of song as part of their attempt to attract a mate. In order to attract a mate, males must use increasingly complex songs; otherwise habituation will occur in the female birds. Habituation refers to a female bird becoming “used” to a sound, so that it no longer captures her attention. Song learning birds, who are able to develop and produce new sound patterns within their lifetime, have been shown to mimic the calls of other birds, perhaps in order to increase the complexity of their repertoire and appear extra impressive. However, this behavior is somewhat paradoxical. Female birds must be able to distinguish calls made by their same species, or conspecific songs, in order to mate with those individuals, and genetically prefer conspecific songs (Miyamoto 2006). The perception of song by other birds plays a crucial role in bird evolution; those males whose songs are successful will mate, reproduce, and pass down their superior song-making abilities.
While the noises produced by dolphins are not technically considered song, they provide a fascinating contrast to the form of vocal communication used by birds. Rather than creating sounds via a syrinx, the sound organ of birds, dolphins vocalize by pushing air through their nasal sacs. Within the nasal region, dolphins have two sets of phonic lips, structures that cause the surrounding tissue to vibrate as the air passes through. However, because studying the anatomy of dolphins as they make noises is difficult, science is not certain about the exact nature of these structures (Dolphin Research Center). Dolphins use their sounds not for mating, as birds do, but in order to communicate. They have been observed to chatter extensively with each other and seem to have their own names- a unique series of clicks and squeaks created by themselves as young dolphins- which they use to signal each other. Their communication capabilities are complex, and many dolphins have been trained to perform tricks that can provide insight into the extent of their capabilities. For example, show dolphins can repeat a series of commands at the signal of a trainer, including a signal to “innovate,” which prompts the water mammals to perform a trick that they have not already performed during that show. This demonstrates a level of understanding beyond mere memorization. More impressive still, a pair of dolphins, when signaled to innovate a trick in unison, will appear to consult each other before performing a new trick, such as blowing bubbles, in perfect synchronicity (Foer 2015). Although projects to determine the extent of dolphin communication and the possibility of a dolphin language are underway, their full capabilities currently remain mysterious.
Perhaps because language is such an innate part of human existence, many become invested in legends like that of a dolphin language. Furthermore, fascinated as we are by ourselves, we yearn to know more about just exactly how special we are; for some, this means studying birds in the hopes to gain insight into the evolution of human speech. Clearly, birds have no difficulties understanding each other, but recent research is working to determine how perceptive birds are to human noises. The verification of this ability would suggest that there is some innate capability within the animal kingdom that allows for the possibility of speech rather than having evolved separately in humans. One study tested this by having birds listen to a variety of people of various sexes pronouncing common English vowels such as /a/ as in hot, /æ/, as in hat, and /ɛ/ as in bet. Additionally, the birds were tested to determine if they could distinguish common consonants /b/ and /p/, or /g/ and /c/. The results showed that birds did indeed possess the ability to differentiate between these human phonemes and remained consistent even when the voices projected were from different speakers. These conclusions add useful information to the timeline of the evolution of speech in humans: some form of phonemic distinction appear evolved long ago, or else emerged convergently (Beckers 2011).
Vocal communication amongst a wide variety of species has always captured the human imagination. Some of the most notable vocalizations are produced by songbirds and play a key role in mating behaviors. By contrast, dolphins use sound to communicate socially and give wonder to viewers with their intelligence and signals to each other. Within both species are many avenues for further exploration. Do dolphins have a language of their own? Why would some birds mimic the cries of other species when this would appear to discourage potential intraspecific mates? There is still much to be learned about both types of organisms, and studying their behaviors gives us as people some perspective as to our place in this world. As we learn more about the shared characteristics in language between ourselves and other species, and consider the evolution of speech, a defining characteristic of humanity, it is humbling to realize that we, too, are all just animals.