At the same time that the human lineage developed speech toolmaking was growing more elaborate. Did these two trends influence one another? The answer obviously is yes, if you believe that speech depends on general human capacities, and just as obviously the answer is no if you believe that speech depends on a specialized language faculty. So I was interested to run across a recent paper that concludes, “… the archaeological record of technological change … document[s] … engagement with materials … [and] neural circuits supporting E[arly] S[tone] A[ge] toolmaking partially overlap with language circuits, strongly suggesting that these behaviours share a foundation in more general human capacities for complex, goal-directed action and are likely to have evolved in a mutually reinforcing way.” It is one more bit of evidence in the humanist side, one more problem for the proponents of specialized modules.
That quotation came from a paper by archaeologist Dietrich Stout and a team of three others (Nicholas Toth, Kathy Schick, Thierry Chaminade in the Philosophical Transactions of the Royal Society B titled “Neural Correlates of Early Stone Age Toolmaking: Technology, Language and Cognition in Human Evolution” (abstract here). It is about the neurology of early-stone-age toolmaking, but it makes two important points for this blog:
- Toolmaking forces engagement with materials.
- Toolmaking and language production brain circuits are supported by some of the same circuits.
Engagement with materials.
Regulars on this blog know about the speech triangle: the speaker, the listener, and the topic. The interest in a neutral topic is one of the peculiarities that separates humans from our ape cousins. Apes and other animals will come to attention when a brute fact of survival is at stake, but they show no interest in neutral topics. It is difficult to find Darwinian reasons to justify an interest in things that don’t matter to one’s survival or ability to reproduce. Yet people talk about just such things. Where did that interest come from? The engagement with materials that is inevitable in working with tools offers a natural transition from interest in survival to a more general interest.
The paper covers the “early stone age,” which lasted from about 2.6 million years ago when the Oldowan tools first appeared until 200/250 thousand years ago when Homo sapiens appeared. In other words, the paper is about the toolmaking efforts of ancestral species.
The oldest tools are called Oldowan, after Olduvai Gorge where the tools were first found. They date from 2.6 million years ago and are cutting tools, sharp-edged “flakes” broken off from a larger stone. They were made by striking a “core stone” with a “hammerstone.” The hammerstone knocks flakes from the core. So we have three tools:
- the hammerstone, which is simply a rock that is picked up and used much as an ape today might use a stone to crack a nut,
- the core which has to be examined closely to determine how best to create flakes, and
- the flake, that has been created by the toolmaking process.
Stout’s team reports that novice Oldowan-tool makers focus their attention on the hammerstone and hitting with it effectively and rhythmically. Experienced makers have the rhythm and action with the hammerstone down to automatic behavior, so they shift their attention to the core stone, its position in space and its details, so that the best flake can be hammered off. Right here we see attention to an early topic, the changing surface of the core stone.
The next set of tools, the Acheulean “hand axes,” were “more-or-less symmetrical, teardrop-shaped tool well suited for butchery and other heavy duty cutting tasks” . The were made by flaking a “blank” from a core stone and then shaping the blank. The process follows three general steps: (1) use a hammerstone to create a roughed out flat stone with a regularly edge; (2) chip off long thin flakes from the blank so that it becomes thinner at the center; and (3) sharpen the edge. This process shows what comes with a more deeply attentive examination of a topic.
About 500 thousand years ago (2 million years after the appearance of Oldowan tools) come the Late Acheulian toolmaking which “seems much more demanding than Oldowan flaking, requiring greater motor skill and practical understanding of stone fracture … more elaborate planning … and an increased number of special purpose knapping tools and technical operations.”  The Oldowan hammerstone has become a group of toolmaking tools, implying a much more detailed understanding of the topic and a closer attention to shaping it.
Thus, the archaeological evidence establishes that the pre-sapiens species were attentive to neutral topics and show a very early date for one of the corners of the speech triangle. It is as old as the genus Homo.
During this whole period of toolmaking, the brains of the toolmakers were growing larger. Stout’s team performed a series of experiments in which they taught people how to make various early stone age tools and then used PET scans to determine which part of the brain were needed to perform the actions. The intriguing finding is that the areas used spread out in a manner consistent with the growth of the brain in the fossils. Oldowan technology depends on the posterior, sensorimotor portions of the brain. The frontal areas, that evolved later, are not necessary even for modern humans making Oldowan tools. Also striking is the way in novice Oldowan toolmakers there is a preference for using the left side of the brain, but experienced artisans use both sides. Language scholars used to say that speech was a left-brain activity, but the right hemisphere is important for speech as well “particularly with respect to larger scale phenomena such as metaphor, figurative language, connotative meaning, prosody and discourse comprehension.”  This pattern matches what we see in Oldowan tool making. Once the organization of an activity is automated the attention can shift elsewhere.
I don’t want to overstate the linkages between the neurology of speech and toolmaking. Stout’s paper says the common denominator in these technical and linguistic tasks is likely the need to coordinate and organize actions to suit the details of the matter at hand. That point sounds about right. The issue of a language faculty, then, is not settled, but the pattern is consistent with the idea that speech arose as part of a broader process of becoming human. Can you do more than shrug it off, if you believe in a language faculty that either made us human or arose for distinct reasons unrelated to the other things that were going on?