On the origins of human articulated speech

Articulated speech is rooted in earlier structures that changed their function and did fossilise. Photo: Daniel Vargas Ruiz / Pixabay

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David Rabadà

Tracing the origins of human articulated speech is no simple task, largely because speech does not fossilise. There are no texts or recordings to tell us when humans first began to speak. What, then, can we do? Inevitably, we must appeal to informed imagination. Evolution works with what is already in place: some structures that initially served no clear function acquire one when they prove advantageous to the organism as a whole, while others lose or transform their roles. Articulated speech is rooted in earlier anatomical structures whose functions were modified—and which, crucially, did fossilise. The challenge, therefore, is to assemble different strands of evidence and identify the point at which they converge.

A first clue lies in the human larynx. In adults, the larynx occupies a low and expanded position, allowing the production of vowel sounds, without which articulated speech would scarcely be possible. In human infants—and in other great apes—the larynx is instead high and narrow. This arrangement enables swallowing and breathing to occur simultaneously. Adult humans cannot drink and breathe at the same time without choking, whereas infants can suckle and inhale concurrently. This ability is gradually lost shortly before the age of two, as the larynx descends to its adult position. In this sense, human infants recapitulate the ancestral evolutionary trajectory of the larynx. Articulated speech is therefore a derived and relatively recent feature in human evolution.

The descent and expansion of the larynx, despite increasing the risk of choking, made articulated speech possible. The persistence of this trait indicates that its evolutionary advantages outweighed the risk of choking. Otherwise, we would not even be speaking about it. The key question, then, is when this capacity emerged. Fortunately, an enlarged larynx leaves traces in a structure that does fossilise: the base of the skull. Some researchers associate a more rounded cranial base with the evolution of this anatomy. Although the interpretation remains debated, such changes appear in late Homo erectus and in all later members of the genus Homo. Moreover, a large larynx requires sufficient space behind the maxilla. Several scholars note that early sapiens already show a marked flexion between the maxilla and the cranial base, dating to around 500,000 years ago. Let us consider whether other lines of evidence support this timeframe.

Another anatomical system linked to articulated speech is the vertebral nervous system. Producing sequences of phonemes, words and sentences requires fine respiratory control. Effective vocalisation and intonation depend on regulated hyperventilation of the lungs. The first hominins to require such efficient pulmonary control were those who colonised open environments—Homo erectus. This adaptation demanded precise control of the diaphragm and later became essential for speech. Articulated language also requires thickened spinal nerves passing through the vertebrae. In early Homo erectus fossils, such as KNM-WT 15000, the vertebral canals are too narrow to accommodate these nerves. The same is true of australopithecines and other great apes. We must therefore conclude that early Homo erectus lacked articulated speech. This anatomical configuration, however, does appear in human fossils dating to around 500,000 years ago.

Speech is also associated with specific regions of the human brain, notably Broca’s area, Wernicke’s area and the supplementary motor area. In sapiens, these regions support many linguistic functions. Importantly, Broca’s and Wernicke’s areas leave detectable impressions on the inner surface of the skull, visible in fossil endocasts. Such impressions are present in Homo heidelbergensis dating to around 500,000 years ago, as well as in later human species. This does not mean, however, that these brain regions always performed the same functions across different species and periods. Broca’s area, for instance, exists in many primates, and cortical folding often obscures its identification. As a result, while suggestive, this evidence cannot be considered decisive.

Another potential correlate of articulated speech lies in lithic technology and cerebral asymmetry. The increase, over the course of human evolution, in the diversity and complexity of lithic tool-making may reflect a corresponding increase in cerebral abstraction. The brain governed the ability to coordinate both hands, a capacity that correlates with cerebral asymmetry. In modern humans, there is a duality between left- and right-handed individuals: in right-handed people, language is processed predominantly in the left hemisphere, whereas in left-handed individuals it is processed predominantly in the right. The same asymmetry underpins stone-tool production. Many lithic assemblages indicate that most of our ancestors were right-handed, and that cerebral asymmetry intensified after Homo erectus.

The progressive enlargement of the left hemisphere—controlling the right hand—may therefore be related to the emergence of speech. This hemisphere hosts most abstract functions, including grammar, verbal memory and logical reasoning, and it contains Broca’s area, Wernicke’s area and the supplementary motor area. Language also requires the ability to imagine utterances in advance, much like imagining a tool, a recipe or a drawing. It is plausible that tool-making, cerebral asymmetry and articulated speech were mutually reinforcing processes during human evolution. Around 500,000 years ago, hemispheric asymmetry became more pronounced, potentially laying the groundwork for the earliest forms of artistic expression—another relevant indicator of articulated language.

Art has often been viewed as a relatively recent phenomenon, centred in Europe around 40,000 years ago. Yet archaeological evidence challenges this assumption. Sites older than 300,000 years show the use of pigments for drawing, bas-reliefs or painting. Examples include the bas-reliefs depicting huts and hearths at Bilzingsleben in Germany (c. 370,000 years ago), the drawn huts at Terra Amata in France (c. 400,000 years ago), and numerous sites containing ochre, likely used for body painting, dating back more than 200,000 years. It is worth noting that body painting for ritual or aesthetic purposes does not fossilise. The absence of cave paintings does not imply the absence of conceptual art. Today, tattoos flourish across the skin of my students.

Taken together, the evidence suggests that by around 500,000 years ago humans possessed the capacity to imagine and to translate imagination into material form. Articulated speech required the same abilities, combined with creativity and symbolic cognition. When modern humans manufacture tools, they activate brain regions involved in sound, abstraction and planning. Articulated language is thus neurologically intertwined with motor coordination, symbolism and tool production. Imagining tools, alternative futures or extended sentences relies on interconnected processes within the brain. These capacities appear to have evolved together from around half a million years ago.

To this picture we must add neoteny—the retention of juvenile traits into adulthood. Neoteny allows the “inner child” to persist, sustaining imagination and enabling the continued formation of new neural connections. The human brain remains capable of learning throughout much of life. Creativity, therefore, underlies our capacities for tool-making, planning and language, supported by extensive neural networks. Cognitive flexibility, memory and attentional control operate simultaneously when we converse, plan or manufacture artefacts.

This broader context also challenges a long-standing assumption in human evolution: that Homo sapiens alone was responsible for conceptual art. As we have seen, earlier members of the genus Homo already displayed such abilities. With Homo sapiens, however, abstract and artistic creativity diversified dramatically. Examples attributed to sapiens include ochre used for body painting at Pinnacle Point in South Africa (c. 165,000 years ago), iron oxide applied to shells at Blombos Cave (c. 100,000 years ago), necklace beads from Skhul in Israel (c. 100,000 years ago), and a decorated bone harpoon from Katanda in the Congo (c. 80,000 years ago). Some researchers associate this expansion of symbolic culture with genetic changes linked to cognitive complexity. The spread of the ApoE3 allele around 200,000 years ago coincides with increased symbolic expression, later reinforced by the emergence of the ApoE2 allele, further enhancing symbolic complexity and human cerebral plasticity.

Perhaps the most significant discovery relating to articulated speech, however, concerns the FOXP2 gene. Present in most mammals, this gene carries a mutation in humans that is essential for sentence articulation. The same mutation has been identified in Neanderthals from El Sidrón cave in Spain. If both lineages possessed this trait, they must have inherited it from a common ancestor. Genetic evidence places this ancestor earlier than 500,000 years ago—a timeframe that aligns closely with the anatomical, neurological and archaeological evidence reviewed here. A plausible origin for articulated speech, then, lies among archaic homo sapiens and their contemporaries living more than half a million years ago

Source: educational EVIDENCE

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