Les Français parlent rapidement à Paris. This translates to the French speak very fast in Paris. A major and obvious change since coming to France has been the language. After being here for a month, I feel as though I’m able to grasp more and more, especially since I’ve been learning French for a long time. However, I still encountered many difficulties such as people automatically speaking to me in English after realizing I’m not a native French speaker. On the other hand, even my friends, with little to no French background, have grasped some French and learned to communicate efficiently most places we go. Either by hearing phrases a lot or communicating with others by gesturing, the French and the Americans can communicate even with a language barrier. It occurred to me how even though the world has so many languages, humans can still communicate universally with one another. If humans can use language to communicate, does language exist in other species too? Well, it depends on how you define language.
There are many ways to define it, which is why many scientists cannot agree on whether some animals have a “language” or not. Language is used for the “purpose of communication is the preservation, growth, and development of the species” (Smith and Miller 1968). If we use this definition, most animals have language because most animals communicate with each other. However, what makes human language unique is that humans have voluntary control of language, while animals use language instinctively (Hedeager 2010)
Another language-related skill unique to humans is vocal production learning (VPL), or the ability to change how and what we say in response to auditory inputs (Janik and Slater 2000; Petkov & Jarvis, 2012). Interestingly, VPL has also been shown to occur in two species of bats, Phyllostomus discolor (P. discolor) and Rousettus aegyptiacus (R. aegyptiacus). Bats are known to communicate through a process called echolocation. Echolocation is the ability to use a biological, built-in sensor to navigate and detect objects. For example, a bat releases high frequency sounds to detect potential prays, and if the sound reflects back from the prey, then it uses this information to hunt. Humans can hear between 10 and 20,000 Hz, while bats detect low-frequency sounds of 1,000 to 200,000 Hz. Frequency is the number of wave cycles that a sound travels in a set time (Biointeractive 2019). Now that we know a little about how bats communicate, we can examine some language-related genetic similarities that are present between us and bats.
One particular study, Rodenas‐Cuadrado et al. (2018), found evidence that three genes, or parts of the DNA passed from parent to offspring, were found to be shared by both bats and humans. FoxP2, FoxP1, and CntnaP2 are well-known genes that are associated with human language (Abrahams et al. 2007). Mutations in the FoxP2 or FoxP1 genes can result in language impairments in children. Mutations in CntnaP2 is known to cause speech and language problems in autism, epilepsy, and intellectual disability (Rodenas‐Cuadrado, Ho, & Vernes, 2014).
Within the study, two species of bats’ brains were studied to determine how much of the three genes were expressed, or active, via immunohistochemistry, a technique to visualize proteins in brain slices (ProteinAtlas 2019).
The researchers organized the results of the three genes found in the bats’ brains by brain region. FoxP2, FoxP1, and CntnaP2 were all found in the cerebral cortex, an area involved in cognitive function, or being able to process sensory output (Rodenas-Cuadrado et al., 2018). FoxP1 and FoxP2 both were abundantly present in the striatum of the brain (Rodenas-Cuadrado et al., 2018). The striatum is involved in echolocation in bats (Tressler et al., 2011) and voluntary motor control in both humans and other species (Hikosaka et al., 2000). Another aspect that the researchers looked at was juvenile (2.5 months old) vs. adult (> 1-year-old) bats. They found that juvenile bats had more gene expression than the adults, which can tell us that the juveniles are still developing to enhance their communication and echolocation. A limitation would be the lack of looking at which brain areas are active when echolocation itself is occurring. This could possibly be done using a functional magnetic resonance imaging (fMRI) tool, where a scan detects certain brain areas activated based on oxygen flow. However, the researchers did examine multiple brain slices, which strengthens the claims where they demonstrate that the three genes are expressed.
Seeing that this study by Rodenas-Cuadrado et al., (2018) examined how bats and humans share three essential language-related genes has made me think that bats and humans are more related than I originally thought! Most animals share a common ancestor who acquired these three language-related genes, but various factors and time brought many changes between species. However, knowing that bats share some language-related genes can open up research on bats and other species to explain how they communicate. Whether it be someone traveling to a foreign country where a different language than their own is spoken or bats using echolocation to communicate, communication is essential to life. Language can mean a lot of things, but in its most basic sense, we all share the process of communicating with one another.
Rodenas-Cuadrado, P. M., Mengede, J., Baas, L., Devanna, P., Schmid, T. A., Yartsev, M., … Vernes, S. C. (2018). Mapping the distribution of language related genes FoxP1, FoxP2, and CntnaP2 in the brains of vocal learning bat species. The Journal of comparative neurology, 526(8), 1235–1266. doi:10.1002/cne.24385
Hedeager, U. (2010). IS LANGUAGE UNIQUE TO THE HUMAN SPECIES?.
Smith, F. and Miller, G.A. eds. (1968) The Genesis of Language – A Psycholinguistic Approach. 3rd ed. (1st ed. 1966). Cambridge Massachusetts and London: The MIT Press.
Rodenas‐Cuadrado P., Ho J., & Vernes S. C. (2014). Shining a light on CNTNAP2: Complex functions to complex disorders. European Journal of Human Genetics: EJHG, 22(2), 171–178.
Tressler, J., Schwartz, C., Wellman, P., Hughes, S., & Smotherman, M. (2011). Regulation of bat echolocation pulse acoustics by striatal dopamine. The Journal of experimental biology, 214(Pt 19), 3238–3247.
Hikosaka O, Takikawa Y, Kawagoe R. (2000) Role of the basal ganglia in the control of purposive saccadic eye movements. Physiol Rev. 80(3):953-78.
Janik V. M., & Slater P. J. (2000). The different roles of social learning in vocal communication. Animal Behaviour, 60(1), 1–11.
Petkov C. I., & Jarvis E. D. (2012). Birds, primates, and spoken language origins: Behavioral phenotypes and neurobiological substrates. Frontiers in Evolutionary Neuroscience, 4, 12.
Language map from https://www.vox.com/2014/7/2/5862696/where-people-speak-what-languages
R. aegyptiacus bat image from https://www.reddit.com/r/BatFacts/comments/2pt451/the_egyptian_fruit_bat_rousettus_aegyptiacus/
Last three images all from Rodenas‐Cuadrado et al. (2018)