Now that we know the general idea of the theory of the evolution of humans, let us discuss some of the physical prerequisites for language in humans.

6.1 Descent of the larynx

Most languages are spoken in their most basic form and thus humans require the ability to pronounce consonants and vowels. This ability is only found in humans and not in other primates such as chimpanzees, evident in the role of descended larynx in humans. However, it is important to note that other non-primate animals have a descended larynx as well, but are unable to use language like humans.

7.1.1 The Human descended larynx

From William T. Fitch’s speech on the Evolution of Language (2005), the larynx, also known as the “voice box” for humans, can engage into the nasal cavity of animals, allowing the ease of breathing while swallowing simultaneously.The larynx in humans is lower than that of other primates, allowing more space for the the tongue to move during speech production.The descended tongue root (i.e. the back of the tongue) allows additional degree of freedom for vocal tract acrobatics during speech production. This mobility of the tongue allows it to produce highly coordinated motions, and therefore giving humans the ability to produce consonants and vowels. The difference in anatomy of other primates’ vocal tracts from humans thus prevent them from speaking well, even with speech training.

6.1.2 The comparative method on descent of the larynx

A descended larynx was believed to be uniquely human until recently. However, it has been shown that animals generally lower their larynx during vocalization (e.g. dog barking) when vocalizing (i.e. producing sounds). Lowering of the larynx during vocalization may hence, be an analogous trait (i.e. traits that are similar in function, but from a different evolutionary source).

Additionally, several species of animals have similarly been observed to possess descended larynx. Examples include koalas, deers and even lions. Since the common mammalian ancestor of these species do not have a descended larynx, this convergence indicates that selective evolution may have taken place. From this discovery, Fitch (2000) proposed that the motivation for the descent of the larynx was not only caused by the need for speech in humans, since this descended larynx in animals did not cause them to speak, unlike the descended larynx in humans.The evolution of the vocal tract thus requires consideration of other factors like selective evolution. Both homology (i.e. similar function, but different evolutionary source) and analogy traits must then be analysed for a comprehensive understanding of human’s capacity for speech.This comparative approach presented by Fitch (2005) then suggests a probable hypothesis that the trait of a lowered larynx may have already been present even before the the humans and chimpanzees species split from a possible common ancestor.Further research was then done on nervous and muscular control to explore other prerequisites for language to account for the reason behind this occurrence. Specific movements of mouth and teeth are crucial to the production of consonants and vowels. Thus, researchers hypothesised that there could be a particular gene in humans that control this fine motor skill, leading to the significance of the research on the FOXP2 gene.
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6.2 Nervous and muscular control – FOXP2

Another physical prerequisite for language in human beings is the presence of the FOXP2 gene. In general, FOXP2 in humans is a gene which codes for oral motor control and speech production in humans. Speech production in human beings require fine nervous control. One of the most evident aspect is that enhanced motor control over vocal articulators like the tongue, lips, jaw, etc., is needed for speech production. For example, the movements of the tongue has to be synchronised with the lips and vibrations of the larynx (voice box) when we speak (Liberman & McKarthy, 2007).

It is important to note that the above discussion on FOXP2 applies to the human variety of the gene. However, since this blog focuses on the features and origins of human language, we will not discuss how this gene codes for other functions in vertebrates other than humans. More information on the differing function of the FOXP2 gene in animals can be found in this this hyperlink.

To conclude this section, both the descent of the larynx, and the presence of FOXP2 in humans are crucial for speech production, and thus are also important in the physical development of humans to produce language. However, in terms of processing and understanding language, we need to also look at the cognitive prerequisites, which brings us to the topic of the next section.
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