Great apes and siamangs—but not humans—possess laryngeal air sacs, suggesting that they were lost over hominin evolution. The absence of air sacs in humans may hold clues to speech evolution, but little is known about their functions in extant apes. We investigated whether gorillas use their air sacs to produce the staccato ‘growling’ of the silverback chest beat display. This hypothesis was formulated after viewing a nature documentary showing a display by a silverback western gorilla (Kingo). As Kingo growls, the video shows distinctive vibrations in his chest and throat under which the air sacs extend. We also investigated whether other similarly staccato vocalizations—the whinny, sex whinny, and copulation grunt—might also involve the air sacs. To examine these hypotheses, we collected an opportunistic sample of video and audio evidence from research records and another documentary of Kingo’s group, and from videos of other gorillas found on YouTube. Analysis shows that the four vocalizations are each emitted in rapid pulses of a similar frequency (8–16 pulses per second), and limited visual evidence indicates that they may all occur with upper torso vibrations. Future research should determine how consistently the vibrations co-occur with the vocalizations, whether they are synchronized, and their precise location and timing. Our findings fit with the hypothesis that apes—especially, but not exclusively males—use their air sacs for vocalizations and displays related to size exaggeration for sex and territory. Thus changes in social structure, mating, and sexual dimorphism might have led to the obsolescence of the air sacs and their loss in hominin evolution.

中文翻译：

---

大猩猩可能会使用他们的喉气囊来发出嘶嘶声和雄性表演

类人猿和暹罗猿 - 但不是人类 - 拥有喉气囊，这表明它们在人类进化过程中丢失了。人类没有气囊可能为语言进化提供线索，但对其在现存猿类中的功能知之甚少。我们调查了大猩猩是否使用它们的气囊来产生银背胸部节拍显示的断断续续的“咆哮”。这个假设是在观看了一部展示银背西部大猩猩 (Kingo) 展示的自然纪录片后提出的。当金戈咆哮时，视频显示他的胸部和喉咙有明显的振动，气囊在其下方延伸。我们还调查了其他类似断断续续的发声——嘶嘶声、性嘶嘶声和交配咕噜声——是否也可能涉及气囊。为了检验这些假设，我们从研究记录和 Kingo 小组的另一部纪录片以及 YouTube 上发现的其他大猩猩的视频中收集了视频和音频证据的机会样本。分析表明，这四种声音都以相似频率（每秒 8-16 次脉冲）的快速脉冲发出，有限的视觉证据表明它们可能都伴随着上躯干的振动而发生。未来的研究应该确定振动与发声同时发生的一致性，它们是否同步，以及它们的精确位置和时间。我们的研究结果符合这样一种假设，即类人猿——尤其是，但不完全是雄性——使用它们的气囊来发声和展示与性别和领土的尺寸夸大有关。因此，社会结构、交配、