Origin of language
From-where-to-what theory

The "from where to what" model is a language evolution model that is derived primarily from the organization of language processing in the brain into two structures: the auditory dorsal stream and the auditory ventral stream. It hypothesizes seven stages of language evolution (see illustration). Speech originated for the purpose of exchanging contact calls between mothers and their offspring to find one another in the event they became separated (illustration part 1). The contact calls could be modified with intonations in order to express either a higher or lower level of distress (illustration part 2). The use of two types of contact calls enabled the first question-answer conversation. In this scenario, the child would emit a low-level distress call to express a desire to interact with an object, and the mother would respond with either another low-level distress call (to express approval of the interaction) or a high-level distress call (to express disapproval) (illustration part 3). Over time, the improved use of intonations and vocal control led to the invention of unique calls (phonemes) associated with distinct objects (illustration part 4). At first, children learned the calls (phonemes) from their parents by imitating their lip-movements (illustration part 5). Eventually, infants were able to encode into long-term memory all the calls (phonemes). Consequentially, mimicry via lip-reading was limited to infancy and older children learned new calls through mimicry without lip-reading (illustration part 6). Once individuals became capable of producing a sequence of calls, this allowed multi-syllabic words, which increased the size of their vocabulary (illustration part 7). The use of words, composed of sequences of syllables, provided the infra structure for communicating with sequences of words (i.e., sentences).

The theory's name is derived from the two auditory streams, which are both found in the brains of humans and other primates. The auditory ventral stream is responsible for sound recognition, and so it is referred to as the auditory what stream. In primates, the auditory dorsal stream is responsible for sound localization, and thus it is called the auditory where stream. Only in humans (in the left hemisphere), is it also responsible for other processes associated with language use and acquisition, such as speech repetition and production, integration of phonemes with their lip movements, perception and production of intonations, phonological long-term memory (long-term memory storage of the sounds of words), and phonological working memory (the temporary storage of the sounds of words). Some evidence also indicates a role in recognising others by their voices. The emergence of each of these functions in the auditory dorsal stream represents an intermediate stage in the evolution of language.

A contact call origin for human language is consistent with animal studies, as like human language, contact call discrimination in monkeys is lateralised to the left hemisphere. Mice with knock-out to language related genes (such as FOXP2 and SRPX2) also resulted in the pups no longer emitting contact calls when separated from their mothers. Supporting this model is also its ability to explain unique human phenomena, such as the use of intonations when converting words into commands and questions, the tendency of infants to mimic vocalisations during the first year of life (and its disappearance later on) and the protruding and visible human lips, which are not found in other apes. This theory could be considered an elaboration of the putting-down-the-baby theory of language evolution.
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