Abstract
The origin of language is one of the most significant evolutionary milestones of life on Earth, but one of the most persevering scientific unknowns. Two decades ago, game theorists and mathematicians predicted that the first words and grammar emerged as a response to transmission errors and information loss in language's precursor system, however, empirical proof is lacking. Here, we assessed information loss in proto-consonants and proto-vowels in human pre-linguistic ancestors as proxied by orangutan consonant-like and vowel-like calls that compose syllable-like combinations. We played back and re-recorded calls at increasing distances across a structurally complex habitat (i.e. adverse to sound transmission). Consonant-like and vowel-like calls degraded acoustically over distance, but no information loss was detected regarding three distinct classes of information (viz. individual ID, context and population ID). Our results refute prevailing mathematical predictions and herald a turning point in language evolution theory and heuristics. Namely, explaining how the vocal–verbal continuum was crossed in the hominid family will benefit from future mathematical and computational models that, in order to enjoy empirical validity and superior explanatory power, will be informed by great ape behaviour and repertoire.
Highlights
Communication in natural and artificial systems rests on three vertices: the encoder, the decoder and the communication channel linking the two [1]
With regards to language origin—the last major evolutionary transition of life on Earth [2]—much attention has been dedicated to the role of the encoder, the receiver and the interactions between the two [19]
The role of the channel [1]—the interval between encoder and decoder that a signal must traverse— in the emergence of language has remained virtually ignored [20]. This knowledge gap is problematic in light of game theory and mathematical models of language evolution [21,22,23]
Summary
Communication in natural (e.g. human language) and artificial systems (e.g. computer language) rests on three vertices: the encoder, the decoder and the communication channel linking the two [1]. To implement an empirical proof of the currently prevailing mathematical models of linguistic evolution, we assessed information loss in wild orangutan voiceless consonant-like and voiced vowel-like calls [7]. The playback playlist included 120, 118 and 249 calls to assess individual ID, context and population ID information, respectively (see more in electronic supplementary material). Three playbacks sessions were conducted, one for each information type: one playlist comprised recordings varying in individual subjects, an other in context and an other in population. Time = 0.5 means it occurred half-way through the call’s duration) These parameters have been found to be strong descriptors of orangutan calls and their informational content [25,28,33].
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