Lameira Adriano R, Hardus Madeleine E
Department of Psychology, University of Warwick, Coventry CV4 7AL, UK.
Independent researcher.
PNAS Nexus. 2023 Jun 27;2(6):pgad182. doi: 10.1093/pnasnexus/pgad182. eCollection 2023 Jun.
Speech is among the most complex motoric tasks humans ever perform. Songbirds match this achievement during song production through the precise and simultaneous motor control of two sound sources in the syrinx. Integrated and intricate motor control has made songbirds comparative models par excellence for the evolution of speech, however, phylogenetic distance with humans prevents an improved understanding of the precursors that, within the human lineage, drove the emergence of advanced vocal motor control and speech. Here, we report two types of biphonic call combination in wild orangutans that articulatorily resemble human beatboxing and that result from the simultaneous exercise of two vocal sound sources: one unvoiced source achieved through articulatory maneuvering of the lips, tongue, and jaw as typically used for consonant-like call production, plus one voiced source achieved through laryngeal action and voice activation as typically used for vowel-like call production. Orangutan biphonic call combinations showcase unappreciated levels of, and distinct neuromotor channels for, vocal motor control in a wild great ape, providing a direct vocal motor analogy with birdsong based on the precise and simultaneous co-control of two sound sources. Findings suggest that speech and human vocal fluency likely built upon complex call combination, coordination and coarticulation capacities that involved vowel-like and consonant-like calls in an ancestral hominid.
言语是人类所执行的最为复杂的运动任务之一。鸣禽在鸣唱时通过对鸣管中两个声源进行精确且同步的运动控制,实现了与人类言语成就相当的壮举。综合且复杂的运动控制使鸣禽成为研究言语进化的卓越比较模型,然而,与人类的系统发育距离阻碍了我们进一步理解在人类谱系中推动高级发声运动控制和言语出现的前体因素。在此,我们报告了野生猩猩的两种双声呼叫组合,它们在发音上类似于人类的口技,是同时运用两种发声源的结果:一种是通过嘴唇、舌头和下颚的发音动作产生的清音源,这通常用于发出类似辅音的叫声;另一种是通过喉部动作和声音激活产生的浊音源,这通常用于发出类似元音的叫声。猩猩的双声呼叫组合展示了野生大型猿类在发声运动控制方面未被重视的水平以及独特的神经运动通道,基于对两个声源的精确且同步的共同控制,提供了与鸟鸣的直接发声运动类比。研究结果表明,言语和人类发声流畅性可能建立在复杂的呼叫组合、协调和协同发音能力之上,这些能力在原始人类中涉及类似元音和类似辅音的叫声。