This blog is strong on the idea that speech is reasonably old, say two million years plus or minus a couple of hundred thousand years, so I'm always on the alert for arguments in favor of a much more recent date. What do they know that I don't?
I was therefore interested to see a new doctoral thesis that argues language is only about 120 thousand years old, younger than Homo sapiens. A book length argument seems about the best way to amass the evidence and determine whether I should rethink my position on language dating. What does, Susan J. Lanyon of the University of New South Wales, have to say that refutes my position and defends her thesis that, "all of the unique cognitive traits attributed to humans arose as the consequence of one crucial mutation, which radically altered the architecture of the ancestral primate brain."
I have some general principles on my side. First, the rise of voluntary control of speech was not a trivial feat. It required the creation of an ability to manipulate the tongue, lips, and jaw with ultra precise synchronization. At the same time, and under the control of a different region of the brain, the sound has to be shaped by the vocal cords.
Second, developing a series of words and conventions for organizing them takes time. It's not enough just to see something and coin a word for it. You have to want to draw attention to an X and distinguish it from Y. Otherwise, you can just call it Y. To make a sentence you have to draw attention to X and Y and state how they are related. That is a tremendous feat, bringing two separate foci of attention together into one understanding. Apes cannot do it.
Both of these achievements, it seems to me, require hundreds of thousands of years, What's more than cannot be simultaneous. First comes control of vocalization, then comes development of vocabulary and syntax. Why not have them coevolve? Probably there was some overlap, but if vocalization was not already well under control when speech began it probably would not have been useful enough to persist. Or if it did persist, the process of coevolution stretches the whole thing out even longer.
But those are logical reasons and science is as hard on a priori reasoning as it is on scripture. So, is there any supporting evidence for language's hyperantiquity?
Some evidence is anatomical. Apes have air sacs while humans don't, probably because, as Bart de Boer has shown, you get more precise articulation without the air sac. (See: Fossil Evidence of Speech?) The loss of the air sac has given humans a different hyoid bone than apes, but the bone is delicate and rarely fossilized. It has been found in a three-million-year-old Australopithecus fossil, in ape form (see: The Selam Fossil), and in an 800 thousand year old Homo fossil, in modern form. By itself that does not settle the matter of an ancient date, but there is a general pattern of anatomical novelties in humans that give fine control over the larynx, lungs, tongue, lips that suggest evolution was shaping our ability to vocalize for a long time. Some of these changes could have been for other purposes, but with all of them together it becomes harder and harder to say that the changes in the organs, nerves, and muscles were just a happy circumstance.
There are also some scenarios, a couple of them based on hairlessness. Robin Dunbar notes that this loss dealt a blow to social grooming, and Dean Falk adds that infants were no longer able to travel by hanging on to their mother's hair. They had to be carried and sometimes the mother had to put the baby on the ground. Dunbar sees language, gossip really, as a substitute for grooming, while Falk sees language as a means for mother and child to maintain contact while the baby was on the ground. The usual complaint against these theories is that although they may show that language could have been useful, they don't show how it got its present form.
But that complaint is overly strong. Vocalizing without speaking could have worked as a grooming substitute and a way of maintaining contact between mother and child. Our ancestors did not have to be gossiping and singing lullabies from the start. And they have identified something critical about human origins that does not produce much discussion—the crisis that was presented by the loss of body hair.
The loss of grooming relationships threatened a breakdown of a bonding mechanism for holding the troop together and it presented a problem for mothers. Children became persistent burdens who were at constant risk of being left behind. These problems had to be dealt with in some way and vocalizing to form bonds and maintain contact is a possibility. I'll leave it to others to propose other solutions. Layton herself offers none. She does not discuss the loss of hair in her thesis, and although she mentions both Dunbar and Falk, in neither case does she cite their work on the relation between hairlessness and speech.
Hairlessness can be dated by the study of lice DNA to 3.3 million years ago, (See: Lousy Timelines.) going back to our lineage's Australopithecine days. At last we have an evidence-based, possible date for the start of vocalization. Infants still go through such a period of meaningless vocalizing today, and it lasts much of their first year as they move from goo to lala lala. We tend to see these sounds as preparation for proper speech, but the babies themselves don't see it that way, and presumably neither did our babbling ancestors, especially if you suppose that the vocalizing went on for a million or more years before the use of words. Perhaps, for as much as half of the period when the human lineage was vocalizing it wasn't speaking at all, merely babbling or cooing.
Ideas like that always sit me up straight, because they cannot be dismissed a priori and they suggest something utterly new. In this case, we are forced to wonder if we have a Papageno period to our history.
Around 2.5 or 2.8 million years ago a series of surprises converge. The true African grassland appears, Homo fossils make their first appearance, the brain starts to get bigger, and a stone technology known as Oldowan emerges. Does it matter? As for the grassland, we are the only primate able to survive on it. Baboons and vervets hang around its edges, but we can walk out into it and live to tell the tale. It is not surprising that a new genus, one able to survive in the new habitat also appears at the same time. How did they do that? Based on that bigger brain evidence, our ancestors began cooperating.
I have discussed the relation between cooperation and brain growth before (see: The Riddle, the Mystery, and the Enigma), so I will limit my observation to saying that cooperation provides a way to move brain growth beyond the 'ceiling' imposed by ape individualism. This intelligence manifests itself in the Oldowan tools, which are not just one more ape tool. Chimpanzee and bonobo tools are used to perform direct tasks such as catching ants or opening nuts. Thus, a chimpanzee may strip a twig of its leaves to form something to poke in a termite mound and snag termites. They are fashioning tools to satisfy their needs.
Oldowan technology takes that process one step further: they fashioned tools to fashion tools to satisfy their needs. The ultimate Oldowan tool is the flake, or cutting blade, but it is made from other tools. First the toolmaker needs to select a core stone and a hammerstone to smash against the core and produce a flake. This difference may sound outlandishly subtle, but it is the difference between thinking tactically and thinking strategically.
By 2.5 million years ago there was a new genus, Homo, which consisted of cooperative groups, capable of rudimentary strategic thought, and already vocalizing. What's more, we know from the evidence of trained apes that those creatures were already smart enough to use words and phrases. Does this sound like a population on the cusp of language? It is not enough to convict (based on evidence beyond a reasonable doubt), but it might well win a civil case in the US courts (based on the preponderance of evidence).
That outlines my argument for speech, at least at the single-word level, having appeared 2.3 to 1.8 million years ago. But even if you hesitate to buy that line--Lanyon is dismissive of cooperation and denies that it ever happened; she considers brain growth to be a reflection of body growth, and takes Oldowan tools to be no different than any other ape tool--the notion of a single mutation 120 thousand years ago transforming ape intelligence into human seems mighty bold. Lanyon has to explain away fire, the Acheulean axe, Mousterian axes, the mining of ochre, and Neanderthal achievements. She knows it and makes a stab at it. I'm not persuaded, but the case is right there online for you to decide yourself.