Open plains are not a level playing field for hominid consonant-like versus vowel-like calls

Abstract

Africa’s paleo-climate change represents an “ecological black-box” along the evolutionary timeline of spoken language; a vocal hominid went in and, millions of years later, out came a verbal human. It is unknown whether or how a shift from forested, dense habitats towards drier, open ones affected hominid vocal communication, potentially setting stage for speech evolution. To recreate how arboreal proto-vowels and proto-consonants would have interacted with a new ecology at ground level, we assessed how a series of orangutan voiceless consonant-like and voiced vowel-like calls travelled across the savannah. Vowel-like calls performed poorly in comparison to their counterparts. Only consonant-like calls afforded effective perceptibility beyond 100 m distance without requiring repetition, as is characteristic of loud calling behaviour in nonhuman primates, typically composed by vowel-like calls. Results show that proto-consonants in human ancestors may have enhanced reliability of distance vocal communication across a canopy-to-ground ecotone. The ecological settings and soundscapes experienced by human ancestors may have had a more profound impact on the emergence and shape of spoken language than previously recognized.

Editorial: The adaptive value of languages: non-linguistic causes of language diversity, volume II

“…Hartmann et al (2024) report that geospatial and historical autocorrelation were not controlled for, because climate changes through time (cf. Roberts, 2018;Gannon et al, 2023). So like languages, we cannot assume that the current state of things was always the same-in linguistics the inverse is known as the uniformitarian principle (Labov, 1972;Walkden, 2019), i.e., that the current distribution of features across languages are the same, similar, or at least useful, for predicting aspects of languages in the past.…”