Hyoid Bones

Or, U.

When I speak to you, you hear sounds quite distinctive in the animal kingdom. My flexibility of sound production, powered by a single, drawn-out breath, is unusual. You hear me, identifying individual words with ease, even though I speak quickly.

One of the characteristics of the production of human language is the physiology of our throats, in which the hyoid bone is of particular interest. It’s a U-shaped bone positioned on the mid-line of the neck between the chin and the thyroid cartilage. Unlike other bones, it’s our only one not connected to other nearby bones. Instead, it’s anchored by muscles from three directions, providing an attachment focus to the muscles of the floor of the mouth and the tongue; also the larynx, and the epiglottis and pharynx. The hyoid bone facilitates a wide range of tongue, pharyngeal and laryngeal movements by bracing these structures alongside one another.

In 1989, the first fossilised Neanderthal hyoid bone was discovered in Israel. It looked a lot like the standard homo sapiens version. Recent 3D X-ray analysis and subsequent computer modelling of how the bone related to the Neanderthal throat showed that the bone – as deduced from micro-stress patterns within it – was used in a similar way to those of ourselves. But does this mean Neanderthals would have sounded like us when they spoke?

Last week I wrote about the qualities of Neanderthal speech, and the idea that they spoke an advanced, but non-compositional language. Authors of prehistory fiction have so far assumed that Neanderthals spoke with words – if a more limited selection, indicating their antiquity – but many these days think that unlikely. My own novel about Neanderthals resurrected from ancient DNA (as yet unpublished) follows the non-compositional language route, with all the communication problems that would entail.

The hyoid bone, then, is critical for making utterances and speaking because it supports the root of the tongue; in every one of our ancestors it doesn’t sit in the correct position to speak like us. But those ancestors would still have been able to make a wide range of sounds, albeit not as wide as we do. Yet the notion that the Neanderthal hyoid bone not only looks like ours but seems to have worked in the same way is indicative of speech. Complex speech… although that doesn’t mean compositional language as a logical consequence.

When we breathe in, then open our mouths to speak, we push air out of our lungs through the larynx, the set of taut, folded muscles and ligaments in the throat forming our vocal cords. As the air passes through, the larynx opens and closes at speed, changing the frequency of the uttered sounds. Precise movements of the larynx muscles then fine-tune the sound’s pitch. Relaxing the folds of the vocal cords produces lower pitches, while tightening them produces higher ones.

Like our ape ancestors, early hominids had larynxes, but apes’ vocal tract openings lead down into a different set of air sacs. Some scientists think these increase the volume of calls, while others believe they’re a way of supporting comparatively heavy neck muscles. As a consequence, however, apes can’t produce the clear, single-frequency tones which are a vital part of human speech.

Neanderthals’ larynxes were larger than those of homo sapiens, and it’s thought likely that their hyoid bones weren’t placed in quite so advantageous a position. This larger larynx and its surrounds affected the timbre of the sounds which emerged from it. Computer models of such organs show that eee and ooo sounds could be produced well; less so our ahh sound, which is more like an uhh. There is also ambiguity over whether or not the i sound could be uttered by Neanderthals. This is important as that sound is used by human brains to indicate size and relative distance of a speaker – a fundamental part of the cultural matrix in which all modern languages exist. Of course, much debate exists over all this, with the input of computer modelling deemed by some to be more of a hindrance than an asset.

Many scientists now think that complex language in homo sapiens began around 125,000 years ago, though evidence for this is, of course, difficult to find. It’s an educated guess. The phrase ‘complex language’ however does not necessarily mean words made up out of endlessly recombined phonemes, for example when applied to Neanderthals. In his superb book The Singing Neanderthal, Steven Mithen describes a form of language which is holistic – that is, uttered in one-off forms – but which is still able, alongside gesture, tone of voice, body language and facial expression, to convey a wide range of information. So, complex language, in the sense of communicating information, does not necessarily mean compositional language.

This area is a mixture of physiological evidence, archaeology, linguistics and computer modelling, and there is much more work to be done. Neanderthal skeletons are relatively rare, so the 1989 find was unusual. We need more skeletons to acquire more evidence about this critical change from holistic to compositional language, and whether or not that change matched the known differences between ourselves and the Neanderthals.