Dieter Wunderlich on the Evolution of Language (Part 2): Mirror Neurons, Gestures, and Imitation

As I already said, according to Wunderlich’s review of the archaeological and primatological evidence, it is likely that homo erectus already possessed a substantial number of the design features that make human language possible. In his presentation, Wunderlich then goes on to speculate about the relationship between language evolution and mirror neurons, neurons that were first observed firing both when a monkey either saw someone perform a grasping movement or performed the grasping movement itself. For Wunderlich the mirror neurons system gives a possible explanation for two crucial features of language:

- Intentionality ( Speaker intends to produce a certain effect in the Hearer)

- Parity (Speaker and Hearer are able to seamlessly switch roles in conversation)

Mirror Neurons also make plausible a gestural origin of language, because (Arbib 2005, Corballis 2003):

- Chimps are much better at controlling their hands than controlling their vocal apparatus, indeed, chimps are able to learn some kind of sign language and other forms of symbolic communication (i.e. via symbol keyboards), but have problems with learning a vocal-based arbitrary communication system

- We still use gestures when talking, and, as Susan Goldin-Meadow has shown, these speech-accompanying gestures are part of an language-independent knowledge system, so that, for example, in some experimental settings children sometimes indicate the right answer with their gestures but still give the wrong answer verbally.

- There are a lot of sign languages spoken either by the deaf or in some religious communities, and these are just as morphosyntactically fully-fledged as any spoken language

- deaf children born to deaf parents learn sign language just as quickly as hearing children learn spoken language

- in deaf children born to hearing parents, who are thus unable to expose them sign language, there is even a phenomenon of so-called home sign, a kind of spontaneously produced “signed pidgin” ,with the intention to communicate and express needs and desires, which exhibits a very rudimentary grammatical and morphological structure, something which speaks for some kind of innate communicative structuring.

- Also, manual gestures often still bear a closer link to their original motivation, and although arbitrary, they may have the tendency to be more transparent as to their iconic motivation, which could make them easier to learn

- If you consider the cognitive implications of toolmaking described in the last post, gestural language would also be a more natural explication of these, especially because they can combine Topic and Comment in a very visual and illustrative manner, namely manual.

- It is also only a small step from ritualized gestures to symbols. In chimpanzees, for example, there is the phenomenon of ontogenetic ritualization, in which the demand to have access to the breast of her mother is ritualized by child and mother: At first the child pushes her mother’s arm away in order to get to the breast, but after a while she just has to touch her mother’s arm so that she lifts it for her child to be able to be breastfed. But this specialized gesture vanishes by the time the child doesn’t need to be breastfed anymore, and every mother-child generation has to develop this ritual anew. Humans somehow transcend this ritualistic confinement and turn behavior like that into long-lasting symbolic behaviors (see e.g. Tomasello 1999: 31f.)

Another advantage of the mirror neuron hypothesis is that it helps understand the instinctive imitation capacities of children, which can not only be seen as a motor of language acquisition and thus further language evolution, but also as a crucial factor in cultural evolution via iterative learning by members of successive generations, each time with slightly differing input. Indeed as recent experiments show, imitation may be one of the key cognitive specializations that sparked the success of the human evolutionary story. Particularly intriguing are experiments done by Victoria Horner and Andrew Whiten from the Unviersity of St. Andrews in Scotland, and Derek Lyons and his colleagues from Yale University: Children aged 3-4 and young wild-born chimpanzees were shown how to get a little toy turtle/ a reward either 1) out of a transparent puzzle box or 2) out of an opaque puzzle box. Here’s the catch: the right solution is much simpler as the one shown by the demonstrator, who includes a lot of unnecessary steps.

(You only have pull out the red thing at the bottom, to get at the reward, but the demonstrator also removes the tube on the tope and pushed a stick intot he box)

The stunning result: In this task, the chimps prove smarter than human children.

If the box is opaque, that is, if chimps and children are unable to look at the internal workings of the puzzle box and are thus unable to assess which steps are necessary and which are unnecessary, both copy all the actions done by the demonstrator.

If however, the puzzle box is transparent, and children and chimps are in principle able to make out which steps are unnecessary and which aren’t, chimps only copy the relevant actions – and human children still copy every action, including all the obviously unnecessary ones.

taken from Horner & Whiten 2005

This phenomenon is called overimitation. For most tasks in the real world whose causal or internal structure we don’t understand, it pays to closely match the behavior of a more knowledgeable person. However, although in general it is a very powerful learning strategy, it often carries a cost and, as it seems, in children this process is sometimes so automatic that it overrides any relevant causal reasoning about the task itself:

“Children who observe an adult manipulating an unfamiliar object show a strong tendency to encode all of the adult’s purposeful actions as causally meaningful, revising their causal beliefs about the object accordingly.” (Lyons et al. 2007: 19756)

Whiten and Horner (2005: 179) concur:

“differences in the behaviour of chimpanzees and children can best be explained by a combination of a differential focus of attention on actions, results and goals, with the latter possibly influencing the interpretation of the actions of the demonstrator as purposeful.”

However, they also see this as part of a more general tendency of adhering to cultural conventions and norms (Whiten and Horner 2005: 164), something which, albeit in a rudimentary form, is also present in chimpanzees (Whiten et al. 2005: 164)

Thus it is certainly right to say that:

“Much of the success of our species rests on our ability to learn from others’ actions. From the simplest preverbal communication to the most complex adult expertise, a remarkable proportion of our abilities are learned by imitating those around us Imitation is a critical part of what makes us cognitively human and generally constitutes a significant advantage over our primate relatives.” (Lyons et al. 2007: 19751)

But is it right then to say that chimpanzees “Don't Give a Hoot About Unnecessary Actions”?

Well the problem is that the experiments of Whiten and Horner where done with wild chimpanzees.

But what about enculturated chimpanzees raised by humans?

Buttelman et al. (2007) tested just that. They used the “rational imitation” paradigm, which features two conditions a) the subjects are shown an action in which the specific manner of the action is not purposive but result from the demonstrator being occupied with something else, e.g. carrying something so that has to use his foot to turn on light. b) the subjects are shown an action in which the demonstrator chooses a specific manner of performance on purpose, e.g., he has his hands free but still chooses to turn on the light with his foot.

taken from Call & Tomasello 2008

Another instance of the paradigm is an experimental setup in which the subject observes someone sitting on a chair with a light-box on the table in front of her. The person has a blanket wrapped around her. Now in one condition a) her hands are occupied (she is shivering and holding the blanket) and she leans forward and illuminates the light with her head, in the other condition b) her hands are free and she leans forward and illuminates the light with her head.

taken from Gergeley et al. 2002

In the experiment done by Gergeley et al. (2002), most 14-Months old human children re-enacted the demonstrator's way to illuminate the light in condition b) but not in condition a). The explanation for this is that in a) they probably see the demonstrator as being forced to use her head because her hands are occupied, whereas in b) they see the demonstrator as rationally choosing to illuminate the light with her head, because had she wanted to use her hands, she would’ve done. They thus encode her performance as causally meaningful and purposive, and re-enact it.

Interestingly, in Buttelman et al’s (2007) study, in both experimental setups presented here, the enculturated chimpanzees also copied

“the demonstrator’s action more often when he freely chose his action than when he was forced to use it by some constraint” (Buttelman et al. 2007: F37).

On a rich interpretation of these results, one could opt for the

“possibility that all great apes possess the ability to understand others’ intentions as rational choices of action plans to achieve goals, but that only some of them are able to show this understanding in these types of experiments due to special attentional or motivational qualities.” (Buttelman et al. 2007: F38).

Thus chimpanzees may even have a rudimentary Theory of Mind, which enables them to

"understand others in terms of a perception–goal psychology, as opposed to a full-fledged, human-like belief–desire psychology (Call & Tomasello 2008: 187)

As to the whole mirror neurons business, and Wunderlich’s remarks, I’m not sure how the socio-cognitive capacity of purpose-encoding rational imitation can bee seen as being motivated by a mirror neuron system, especially when it comes to language evolution. The language evolution link was motivated by the hypothesis that the premotor cortex of the macaque brain, which is the place where most mirror neuron activity takes place, was an evolutionary cousin, a homologue, to Broca’s Area in humans. But as recent research has shown, this is not the case, and Broca’s Area doesn’t show any mirror neuron activity. (Morrin & Grezes 2008).

I will return to Wunderlich’s presentation in my next post (If I proceed in this manner I’m going to spend the whole year writing about his presentation, given that today’s elaborated on a single slide and I’ve only reached page 10 of 29…)

References:

Arbib, Michael A. (2005) From monkey-like action recognition to human language: An evolutionary framework for neurolinguistics. Behavioral and Brain Sciences, 28(2):105--124.

Buttelmann, David, Malinda Carpenter, Josep Call, and Michael Tomasello (2007). Enculturated chimpanzees imitate rationally. Developmental Science 10.4: F31-8. doi:DESC630.

Call, Josep, and Michael Tomasello. (2008): Does the chimpanzee have a theory of mind? 30 years later. Trends in Cognitive Sciences 12.5: 187-192. doi:10.1016/j.tics.2008.02.010.

Corballis, Michael C. (2003) From hand to mouth: The gestural origins of language. In M.H. Christiansen and S. Kirby, editors, Language Evolution: The States of the Art. Oxford University Press.

Gergely, György , Harold Bekkering, and Ildikó Király. 2002. Developmental psychology: Rational imitation in preverbal infants. Nature 415 (February 1): 755.

Horner, Victoria, and Andrew Whiten. (2005): Causal knowledge and imitation/emulation switching in chimpanzees (Pan troglodytes) and children (Homo sapiens). Animal Cognition 8.3: 164-81. doi:10.1007/s10071-004-0239-6

Lyons, Derek E., Andrew G. Young, and Frank C. Keil. (2007): The hidden structure of overimitation. Proceedings of the National Academy of Sciences 104, no. 50 (December 11): 19751-19756. doi:10.1073/pnas.0704452104

Morin, O., and J. Grezes. (2008) What is “mirror” in the premotor cortex? A review. Neurophysiologie Clinique/Clinical Neurophysiology 38, no. 3 (June): 189-195. doi:10.1016/j.neucli.2008.02.005.

Tomasello, Michael (1999): The Cultural Origins of Human Cognition. Cambridge, Massachusetts; London, England: Harvard University Press

Whiten, Andrew, Victoria Horner & Frans B. M. de Waal. (2005): “Conformity to Cultural Norms of Tool Use in Chimpanzees.” Nature 437: 737-740.

Merry Christmas! (& Memes & Mirror Neurons)

So this is my last post before I’ll be heading home over the holidays.

As I tried to show in this post, it seems that the ability to imitate is crucial for learning a language. Most importantly, it also seems to be a major foundation of all human culture.

There is whole lot of research done in this field and there are hot discussions about the relationship between mirror neurons, imitation, Theory of Mind, language acquisition, language evolution, human cultural evolution, etc.

Memetics, for example, sees our ability to adopt cultural and cognitive patterns of behavior as mediated by our imitative abilities (Blackmore 2007). In 2005 Nick Chater and Susan Hurley published and edited Perspectives on Imitation: From Neuroscience to Social Science, a two volume monstrosity with 1024 pages covering Mechanisms of Imitation, Imitation in Animals, Imitation and Human Development as well as Imitation and Culture, This underlines the renewed appreciation of the importance of imitation as a fundamental property of cognition, instead of an uninteresting low-level phenomenon. (McEwen 2007)

The notion of a link between human culture and cognition on the one hand, and imitation and learning on the other, is of course not new – as we have seen in the passage of Puttenham’s Arte of Poesie I quoted in my last post on imitation. If you look up “imitative” in the OED, you find a 1777 quote by David Hume, who wrote that

“The human mind is of a very imitative nature”

as well as the assessment that

“At present, we are become an imitative, not to say a mimic, race” (in Gifford’s 1827 introduction to the plays of John Ford).

We can trace this notion as far back as to Aristotle, who in his Poetics, claimed that mimesis, the representation or imitation of a state in the world in the form of action, art, or speech, is a fundamental property of human cognition. Interestingly, he describes imitation as an “instinct of our nature” and writes that:

“the instinct of imitation is implanted in man from childhood, one difference between him and other animals being that he is the most imitative of living creatures, and through imitation learns his earliest lessons;”

As it seems, Aristotle’s assessment is indeed backed up by behavioral evidence. 30 years ago, Meltzoff and Moore (1977) found that 12 to 21-day old infants were able to imitate the experimenter’s facial gestures of mouth opening, lip protrusion and, tongue protrusion, as well as manual gestures such as the opening of the hand. In a follow-up study, they showed that even newborns who are less than 72 hours old are able to imitate these gestures (Meltzoff & Moore 1989). Interestingly, this tendency seems to disappear between two and three months of age. This is probably explained by the fact that autonomously controlled, spontaneus face-to-face social interaction (as a baby smiling at her mother, for example) kicks in around this time and infants start to communicate intentionally. (Myowa-Yamakoshi et al. 2004: 441)

Now is this a uniquely human trait?

Quite astonishingly, Myowa-Yamakoshi et al. (2004) found that chimpanzees who are less than 7 days old are also able to imitate the gestures of tongue protrusion, mouth opening, and lip protrusion.

As in humans, this tendency disappeared at two months of age. The authors conclude that
“like human neonates, chimpanzee neonates are born with the ability to match visually perceived oral gestures with a proprioceptive motor schemes .“ (Myowa-Yamakoshi et al. 2004: 440).

So what about other primates? Previously it was thought that only humans and apes posses these neonatal skills, but it seems that at 3 days of age, rhesus macaques are able to imitate lip smacking and tongue protrusion (Ferrari et al. 2006), facial gestures which later become important in social interaction (Gross 2006)

However, the macaques showed this behavior only a few days after birth and after that it vanished. This may be due the fact that motor as well as cognitive development in macaques is much more rapid in macaques than in the higher apes. It thus seems that the more advanced human imitation capacities built on these imitative foundations that must have been present at the time our lineage split from that of macaques, namely 25 million years ago.
Interestingly, macaques were the first species in which mirror neurons – neurons that fire both during the performance as well as during the observation of an action – were found, and hopefully there will be more studies on the neural basis of imitation in macaques.

Quite Remarkably, adult macaques are also able to notice when someone else is imitating their actions (e.g. a human experimenter), but it is unclear whether they are able to grasp the fact that the experimenter is intentionally imitating them, or if they just recognize it implicitly (Paukner et al. 2005). In the second case, the macaques would just exhibit this knowledge via metacognition, i.e. the awareness of some inner state, something which macaques seem to be able to do.
Evidence for metacognition in macaques comes from research done by H.S. Terrace and his team, who taught their macaques a matching game, and then offered them the options to either play the game and get some food if they won and nothing if they lost, or the option to not play the game and get less food. Interestingly, sometimes the macaques chose the latter, option, and sometimes they chose the former, but if they chose the first option, they performed pretty well, indicating that the macaques had a means of assessing how accurate they were at getting the game right. In another experimental setting, macaques also learned to ask for hints if they otherwise had to solve the problem by trial and error, again indicating that they had some metacognitive means of assessing what they knew and what they didn’t (Kornell et al. 2007).
It is much more questionable if macaques exhibit metarepresentation, i.e. the awareness of mental states of others (Hurford 2007: 35)

This of course taps into the discussion of which primates exhibit a Theory of Mind, or an awareness of the mental states of others, and whether the transition from nonhuman to human minds should be seen as continuous or discontinuous. The two main camps in this debate are that of Povinelli and his colleagues on the one side, who argue that nonhuman primates do not exhibit abstract inferences of others mental states, and that there is a qualitative gap between human and nonhuman cognition (Povinelli & Vonk 2003), and Tomasello and his team on the other side, who argue that chimpanzees are able to understand some psychological states to a certain degree, and that human cognition should be seen as much more continuous (Tomasello et al. 2003). It seems as if Povinelli and his colleagues are just about to launch their next major attack (to be publish in the journal Behavioral and Brain Sciences in 2008) awe-inspiringly called “Darwin’s mistake: Explaining the discontinuity between human and nonhuman minds” . As BBS consists of the target article along with 25 or so commentaries other researchers, I’m really interested in how this will turn out.

For now it is quite interesting enough (and also somewhat amusing) how both parties assess the importance of the debate:

Whereas Tomasello et al. (2003) claim that:

“At issue is no less than the nature of human cognitive uniqueness” (Tomasello et al. 2003: 156)

Povinelli et al. take a much more relaxed stance:

"the idea that theory of mind is the ‘holy grail’ of comparative cognition needs to be abandoned. Neither chimpanzees nor evolutionary theory will be insulted if the very idea of ‘mental states’ turns out to be an oddity of our species’ way of understanding the social world.“ (Povinelli et al. 160)

Dang, I still haven’t posted about either the Lyons et al. (2007) paper or the genetic differences between humans and chimpanzees. But I will do so next year. Promise. Cross my Heart and Hope to Die. As an apology, here’s a link to a great song by Jonathan Coulton, performed live in front of an audience of (judging by the chorus) zombies. Gotta love that.

So merry Christmas & Happy New Year, and see you in 2008.

References:

Blackmore, Susan. 2007. “Those dreaded memes: The advantage of memetics over “symbolic inheritance.” Behavioral and Brain Sciences 30.4: 365-366.

Ferrari PF, Visalberghi E, Paukner A, Fogassi L, Ruggiero A, et al. (2006) Neonatal imitation in rhesus macaques. PLoS Biol 4(9): e302. DOI: 10.1371/journal.pbio.0040302

Gross L (2006) Evolution of Neonatal Imitation. PLoS Biol 4(9): e311 doi:10.1371/journal.pbio.0040311

Hurford, James M. 2007. The Origins of Meaning: Language in the Light of Evolution. Oxford: OUP.

Kornell, Nate, Son, Lisa K. and Herbert S. Terrace. 2007. “Transfer of Metacognitive Skills and Hint Seeking in Monkeys. Psychological Science” 18.1: 64-71.

McEwen, Fiona. 2007. “Review: Perspectives on Imitation: From Neuroscience to Social Science.” Mind & Language, 22.2 April : 207–213

Meltzoff AN, Moore MK .1977. Imitation of facial and manual gestures by human neonates. Science 198: 75–78.

Meltzoff AN, Moore MK (1989) Imitation in newborn infants: Exploring the range of gestures imitated and the underlying mechanisms. Developmental Psychology 25: 954–962

Myowa-Yamakoshi M, Tomonaga M, Tanaka M, Matsuzawa T .2004. “Imitation in neonatal chimpanzees (Pan troglodytes).” Developmental Science 7: 437–442

Paukner A, Borelli E, Visalberghi E, Anderson JR, Ferrari PF (2005) Macaques (Macaca nemestrina) recognize when they are being imitated. Biology Letters 1: 219–222.

Povinelli, D.J. and Vonk. J. (2003) Chimpanzee minds: Suspiciously human? Trends in Cognitive Sciences, 7.4, 157–160.

Tomasello, Michael, Josep Call and Brian Hare. 2003. Chimpanzees understand psychological states – the question is which ones and to what extent. Trends in Cognitive Sciences, 7- 153-156.

Well, Mimes Still Suck

So in my last post I wrote about the importance of vocal imitation for the evolution of language. According to Hauser et al. (2002), it is one of the most important species-specific, but not language-specific components that make up the faculty of language in the broad sense (FLB), as opposed to the faculty of language in the narrow sense, (FLN), which they equate with the

"core computational mechanisms of recursion as they appear in narrow syntax and the mappings to the interfaces [of the conceptual-intentional system (e.g. vocal imitation, sound-pattern discrimination, language perception and production, etc.) and the sensory-motor system(e.g. Theory of Mind, nonlinguistic conceptual representations, voluntary control over signal production, etc.) - and whatever you think should be seen as a part of it, Hauser et al. don't care]" (Hauser et al. 2002: 1573)

Whatever that is supposed to mean.
Hauser et al. also list

"Imitation as a rational, intentional system" (Hauser et al. 2002: 1573)

as a component of the conceptual-intentional system, and cite

"Comparative studies of chimpanzees and human infants suggesting that only the latter read intentionality into action, and thus extract unobserved rational intent" (Hauser et al. 2002: 1573).This remark touches upon the messy theory of mind debate in the cognitive sciences and elsewhere. Hauser et al. seem to assume that there is an intrinsic link between some forms of imitation and the attribution of intent to the other. They report that chimpanzees seem to have only minimal visual-imitative capacities, and that there is almost no evidence for them in monkeys (Hauser et al. 2002: 1575). According to Hauser et al. this seems to confirm that non-human apes and monkeys are not able to attribute intentions to others.

However, it seems that chimpanzees at reading others behavioral programs, and predicting their future actions without needing to attribute mental states to con-specifics. (Byrne and Russon 1998) In general, just as language is not a monolithic whole, imitation probably is also a cognitive capacity consisting of various component parts. Byrne and Russon (1998) propose that Imitation is in fact a task that is hierarchically divided in separate forms of imitation, that is

1. Imitation as Goal Imitation (i.e. achieve the same result, e.g. eating a fruit, possibly in a roughly similar as someone before you).
   
2. Imitation at the Program Level (i.e. simulate the actions at a broad behavioral level, representing the organizational structure of an action, without imitating it in detail)
   
3. Impersonation, or "True Imitation" (i.e. simulate the other's motoric actions in detail)
   

According to Byrne and Russon (1998), all great apes are able to imitate behavior at the second level, and the use of "action level" imitation is primarily restricted to humans (although they speculate that in non-human great apes, this may be more a matter of motivation than ability), but only plays a minor role, because even such complex skills as the learning of language (e.g. sound production) are achieved on the program level because they do not actually imitate the physical sounds but the organizational structure of the sound system. However, they don't really come up with a good explanation why action level imitation exists in humans at all, and even doubt that it plays an important or even frequent role at all.

As Tomasello (1998) rightly criticizes, this largely downplays the role of shared human cultural and cognitive artifacts and the creative use to which they can put in order to facilitate new functional dimensions and therefore progress, and fails to explain what it is that is special about humans, and why cultural transmission in humans is so much more powerful than in other apes.
They also greatly underestimate the importance of the arbitrary, conventionalized nature of the (Saussurean) linguistic sign, which is crucial for the establishment of a successfully communicating group of agents (Which is also why my blog's title alludes to this principle. I'll come back to this in a subsequent post)
I think it is interesting to contrast Byrne and Russon's model with evidence of so-called conformity bias in chimpanzees.
Whiten et al. (2005) taught two distinct tool-use techniques to two high-ranking female chimpanzees, and then brought them back to their groups. 30 of 32 chimpanzees adopted the female chimpanzees technique. Some chimpanzee at first discovered different means of tool-use, which could be explained in terms of broad organizational imitation, but later also adopted the predominating technique of their group, even if they were able to use both techniques and both very equally successful. If chimpanzees would act only at a broad behavioral level, then this effect surely wouldn’t have occurred. Thus, there is evidence that even in chimpanzees there is the convergence of complex behavioral patterns (we could even call them ‘memes’ if we felt like it) to a cultural norm. Thus, such tendencies must have a deeper evolutionary heritage than assumed before.
Furthermore, Byrne and Russon write that

"We suspect, however, that action level imitation is less common in children than it seems, and that, often, children’s “imitation” may reflect response facilitation." (Byrne and Russon 1998: 683)"

This, however, is clearly refuted by experiments done by Lyons et al. (2007), which I will describe in my next post. (In the meantime, however, you should rather go read Carl Zimmer's heartening and much more enjoyable blog post and article in the New York Times about the fate of his daughter in comparative tests between human children and chimpanzees. )
Without question, Byrne and Russon's model is not able to give a complete theory of imitation, which is why I will look at some other approaches in my next post

References:

Byrne, Richard W and Anne E. Russon. 1998. “Learning by Imitation: a Hierarchical Approach.” Behavioral and Brain Sciences 21.5: 667-684

Hauser, Marc D., Noam Chomsky and W. Tecumseh Fitch 2002. “The Faculty of Language: What Is It, Who Has It, and How Did It Evolve?” Science 298: 1569-1579.

Lyons, Derek E.. Andrew G. Young, and Frank C. Keil. 2007. “The Hidden Structure of Overimitation” PNAS 105.50: 19751–19756.

Tomasello, Michael. 1998. “Emulation learning and cultural learning.” Behavioral and Brain Sciences 21.5: 703-704.

Whiten, Andrew, Victoria Horner & Frans B. M. de Waal. 2005. “Conformity to Cultural Norms of Tool Use in Chimpanzees.” Nature 437: 737-740.

Oh, I Forgot Something

In my last post I wrote that two main approaches to comparing human and other animals’ cognition are ethological and genetic comparisons, but I think with such a statement I strongly downplayed the importance of anatomical features when comparing two species, such as the differences in brain anatomy (for a stake at this topic, see my earlier posts on brain evolution), and other features that bear a more indirect bearing on the structure of human cognition, yet it has a much stronger bearing on questions of human uniqueness.

These considerations are of course not exactly new. as early as in 1589, for example, George Puttenham wrote in his Arte of English Poesie that:

“Speach is not naturall to man sauing for his onely habilitie to speake, and that he is by kinde apt to vtter all his conceits with sounds and voyces diuersified many maner of wayes, by meanes of the many & fit instruments he hath by nature to that purpose, as a broad and voluble tong, thinne and mouable lippes, teeth euen and not shagged, thick ranged, a round vaulted pallate, and a long throte, besides and excellent capacitie of wit that maketh him more disciplinable and imitatiue then any other creature […].”

I will stick with this example because language evolution is this blog’s main topic.
What I find interesting in this paragraph is that Puttenham actually directs attention to a lot of physiological features that are acknowledged by modern linguists and phoneticians to be crucial for the production of speech. As Jean Aitchision puts it, we are “The Articulate Mammal” (1998), and many of her observations actually concur with that of Puttenham.
Just as he does she stresses the difference between the long thin tongues of monkey and the muscular, thick and mobile tongues of humans, which allows them to vary the size of the oral cavity, and thus allows the pronunciation of a great range of vowels.
She also stresses the fact that the muscles in the lips of humans are more intricately interlaced and more developed than the muscles in the lips of other primates. Aitchision also observes that the regularity of human teeth is not needed for eating but probably for articulatory purposes. (Aitchison 1998: 48f., Lieberman 2007: 40-47 , Fitch 2005: 198f.)

I doubt that Puttenham was the first to notice the importance of the specially structured and descended larynx of humans for speech, but he definitely wasn’t the last. Whereas in most mammals, simultaneous breathing and swallowing is possible, humans (or at least those who aren’t babies anymore), don’t posses this ability because their larynx lies too low to be engaged into the nasal passages. (Fitch 2000: 260)
This anatomical change expands the vocal repertoire of humans significantly and can be seen as “a key innovation in the evolution of speech” (Fitch 2000: 261) because it enabled us to form highly discriminable different phonetic sounds (“formant patterns”) (Fitch 2000:261),
However, it has lately been discovered that animals exhibit a remarkable plasticity in regards to the lowering of the larynx during vocalization (for a example, a dog bark) Furthermore, the descension of the larynx doesn’t seem to be unique to humans, and is also found in lions, koalas, and deer. (Fitch 2005: 199).

This has led some researchers, such as Tecumseh Fitch, to suggest that this shared property is an instance of convergent evolution and thus evolved for a different purpose than speech production, namely size exaggeration, the function the descension of the larynx fulfills, for example, in deer (Fitch and Reby 2001, Fitch 2005).
In this view, the descension of the larynx was prior to speech and was only later co-opted for language. The first fully modern human speech anatomy is dated to 50,000 years ago, and is missing in earlier humans as well as Neanderthals. (Lieberman 2007). This still fits with the a scenario in which the speech tract was only later adapted and further shaped for language, and it definitely shows that language/speech is a driving force in human evolution, given the long evolutionary trajectory it has had.

But what then, is special to speech? Again it seems that Puttenham was on the right track. Hauser et al. (2002), for example, also stress the importance of vocal imitation in language learning and production. Whereas dolphins, whales, seals, songbirds, parrots, hummingbirds and some other species seem to share humans’ aptness regarding vocal imitation, it seems that in other primates this trait is either absent or only exists in a rather rudimental form (Hauser et al. 2002, Fitch 2000, Fitch 2005).
This is supported for example by evidence from cross-fostered Japanese/rhesus macaques. Although both species have a very similar social structure, their vocalizations are quite different in some context. Whereas juvenile Japanese macaques give clear cooing sounds when playing, rhesus macaques give gruffy grunts in the same situation. Did the Japanese macaques growing up in the Rhesus macaque adopt the vocalizations of their foster species? What about the Rhesus macaques growing up among Japanese Macaques?
Interestingly, although they are in fact able to produce such sounds (and do so in other contexts), the Japanese Macaque splaying with Rhesus macaques gave coos whereas their playmates gave gruffs. The same lack of vocal adaptation could be seen in the cross-fostered rhesus macaques. Certain calls in the macaques seem to be genetically bound to specific contexts(Cheney & Seyfarth 2007: 225, Owren et al. 1993), something which clearly isn’t the case with humans (otherwise there wouldn’t be 250 different languages spoken alone in Brooklyn, for example).

So the case Hauser et al. make for vocal imitation seems quite a strong one. Yet, as they themselves acknowledge, the question what vocal imitation evolved for is still hotly debated. There is still further evidence that supports the notion that vocal imitation is a more crucial component that led to human language than mere voluntary vocal control per se.
As we have seen, in some situations primate and generally animal signaling is closely bound to specific contexts. However, there are other situations where call production is much more plastic and seems to be much more under voluntary control.

One example is a study by Hihara et al. (2003), in which they trained macaques to use a rake in order to retrieve food, and subsequently brought them to either request the food directly, or request the rake, via cooing (Something the monkey is probably inclined to utter naturally in the context of food.) Astonishingly, the monkeys came up with two distinct calls all on their own, one for requesting the rake, the other for requesting for food (Cheney & Seyfarth 2007: 227, Hihara et al. 2003).
An even more intriguing example of signal transformation (albeit not in the auditory modality), called schematization of action, is the following: (Which I took from Hurford 2007, who took it from Gomez 2005 – yeah, recursion rocks!)

“Thorndike (1898) found that cats that were released from a puzzle-box upon performance of an arbitrarily chosen action (e.g., licking their paw), instead of by the accidental activation of the releasing device, tended to develop an abridged, sketched-out version of the relevant behaviour — something like a “gesture” of paw-licking“ (Gomez 2005: 93, Hurford 2007: 199,)

Of course, Puttenham wasn’t only referring to vocal imitation. In fact, things lie a bit differently when we speak about general imitation, and I’ll discuss some of the evidence on human vs. non-human imitation in my next post.

References:

Aitchison, Jean. 1998. The Articulate Mammal. An Introduction toPsycholinguistics. London / New York: Routledge.

Cheney, Dorothy L. and Robert M. Seyfarth. 2007. Baboon Metaphysics: The Evolution of a Social Mind. University of Chicago Press, Chicago

Fitch W. Tecumseh. 2000. The evolution of speech: a comparative review. Trends in Cognitive Sciences. 4: 258 – 267.

Fitch, W. Tecumseh. 2005. “The Evolution of Language: A Comparative Review” P Biology and Philosophy 20: 193–230

Fitch, W. Tcusmeh and David Reby. 2001. “The descended larynx is not uniquely human.” Proclamations of the Royal Society B: Bioliogical Sciences 268: 1669 – 1675.

Gómez, Juan Carlos. 2005. “Requesting gestures in captive monkeys and apes: Conditioned responses or referential behaviours?“ Gesture 5.1/2: 91-105.

Hauser, Marc D., Noam Chomsky and W. Tecumseh Fitch 2002. “The Faculty of Language: What Is It, Who Has It, and How Did It Evolve?” In: Science 298, 1569-1579

Hihara, Sayaka, HirokoYamada, Atsushi Iriki, and Kazuo Okanoya. 2003. “Spontaneous vocal differentiation of coo-calls for tools and food in Japanese monkeys” Neuroscience Research 45.4

Hurford, James M. 2007. The Origins of Meaning: Language in the Light of Evolution. Oxford: OUP.

Lieberman, Phillip. 2007. “The Evolution of Speech: Its Anatomical and Neural Bases.” Current Anthropology 48.1: 39-66.

Owren MJ, Dieter JA, Seyfarth RM, Cheney DL.. 1993 “Vocalizations of rhesus (Macaca mulatta) and Japanese (M. fuscata) macaques cross-fostered between species show evidence of only limited modification “ Developmental Psychobiology 26.7: 389-406.

Thorndike, Edward L. 1898. “Animal intelligence: An experimental study of the associative processes in animals.” Psychological Review: Series of Monograph Supplements, 2.4: 1-109.