Main Text (Word count: 1197) 23Language and music are peculiar human behaviors. We spend a large portion of our lives speaking, 24 reading, processing speech, performing music and listening to tunes. At the same time, we still know very 25 little as to why and how these structured behaviors emerged in our species. For the particular case of 26 music, the mystery is even greater than language. Music is a widespread human behavior which does not 27 seem to confer any evolutionary advantage. A possible approach to study the origins of music is to 28 hypothesize and empirically test the mechanisms behind this structured behavior [1, 2]. For language, 29 potential mechanisms were first tested in-silico [3, 4], showing how random pairs of signal-meanings 30 become more structured and systematic when artificial agents play a 'game of telephone' with them. 31These results were replicated with human participants evolving a language-like system [5], confirming the 32 importance of computer simulations in testing hypotheses on the cultural evolution of human behavior. 33Finally, recent work applied this approach to musical rhythm [6], showing that musical structures can 34 indeed emerge via cultural transmission . 35
36A recent paper in Artificial Life adopted this methodological approach, testing the emergence of a sound 37 system at the boundary between music and language [7]. Similar to communication systems found in 38 humans, other animals and in-silico experiments, a meaning space was paired with a signal space. The 39 meaning space coincided with a set of pictures showing different facial emotional expressions. The signal 40 space was a set of 5-note patterns. Crucially, the experimenters randomly paired meanings to signals, 41 which were in turn randomly structured. These random pairings of emotional expressions and random 42 note sequences were then used in signaling games, where pairs of participants used note sequences to 43 communicate emotional states. The resulting signal-meaning pairs, with all their human-introduced 44 variations, were then used in new signaling games with new participants. Over time, the small biases 45 introduced in each artificial transmission step accumulated, displaying quantitative trends. In particular, 46 the authors found the emergence, over the course of artificial human generations, of features resembling 47 some properties of language and music.
49A number of methodological solutions make this paper quite valuable. For instance, an obvious potential 50 confound when mapping proto-musical structures to emotional states is that some of these mappings are 51 already ingrained and universal in human cognition [8]. The authors circumvent this potential confound 52 by using the Bohlen-Pierce (BP) scale [9], to which the average human being is never exposed, rather 53 than the common 12 tone equal temperament scale (the black and white piano keys). 54
55For centuries, the study of music has been the sole prerogative of the humanities. Lately, however, music 56 research is being increa...