Department of Psychology, University of Warwick, Coventry, UK.
Department of Anthropology, Durham University, Durham, UK.
Sci Rep. 2023 Dec 21;13(1):21138. doi: 10.1038/s41598-023-48165-7.
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.
非洲古气候的变化代表了语言进化历程中一个“生态黑箱”；一个有发声能力的原始人走了进去，数百万年后，一个会说话的人类走了出来。目前还不清楚从森林茂密的栖息地向干燥开阔的栖息地的转变是如何影响原始人类的发声交流的，而这种转变可能为语言进化奠定了基础。为了重现树栖原始元音和辅音与地面新生态系统的相互作用，我们评估了一系列猩猩无声辅音样和有声元音样叫声在热带稀树草原上的传播方式。与它们的同类相比，元音样叫声表现不佳。只有辅音样叫声在不需要重复的情况下，能够在 100 米以外的地方有效地被感知，这是一种非人类灵长类动物大声呼叫行为的典型特征，通常由元音样叫声组成。研究结果表明，人类祖先的原始辅音可能增强了在树冠到地面生态过渡带进行远距离声音交流的可靠性。人类祖先经历的生态环境和声音环境对口语的出现和形成的影响可能比以前认识到的要深远得多。
