Hoover was an orphaned harbour seal pup picked up and raised by fisherman in Maine (Cundy Harbor Maine on May5 1971). After Hoover became too large, he was donated to the New England Aquarium in Boston, Massachusetts. When he began to become sexually mature, Hoover began to make speechlike sounds. By 1978, at the age of seven, an incredulous observer wrote in the aquarium files “he says ‘Hoover’ in plain English. I have witnesses”. Unfortunately, Hoover died in 1985.

Why is vocal learning in seals important (or, why should a scientist care about a talking seal)? A short answer is here

For more detail about Hoover, see: Ralls, K., P. Fiorelli, and S. Gish, Vocalizations and vocal mimicry in captive harbor seals, Phoca vitulina. Canadian Journal of Zoology, 1985. 63: p. 1050-1056.

There is also a web page on Hoover at the New England Aquarium: Hoover Page

Here are some recordings of Hoover (made in 1981 by Katherine Ralls, and some time later by Terrence Deacon):

Hoover1

Hoover2

Hoover3

(or, why should anyone care about talking seals?)

Vocal learning – the ability to imitate complex vocalizations – is a relatively rare ability in the animal kingdom. Humans obviously are excellent vocal learners, and this ability is central to both singing and speech. Surprisingly, vocal learning of complex sounds (like speech or songs) has not been found in ANY other nonhuman primate.

However, vocal learning is common among birds, and at least three major bird groups have evolved vocal learning, probably independently: the songbirds (oscine passerines), parrots, and hummingbirds. This has led to songbirds becoming the major group in which the genetic and neural basis for vocal learning is studied. Unfortunately, however, birds have both a very different brain from that of mammals, and a completely novel vocal production system (called the syrinx). Thus, there may be important differences between vocal learning mechanisms in humans and birds.

Another large group of vocal learners are the cetaceans: whales and dolphins. Again, unfortunately the mechanism dolphins and other toothed whales use to make sounds is evolutionarily novel, and unrelated to the human vocal tract. Cetacean brains are also rather peculiar, with a very thin cerebral cortex. Thus, the similarities between cetacean vocal learning mechanisms and our own may be quite circumscribed.

Are there ANY animals capable of complex vocal learning, that have brains and vocal tracts like ours? Yes: many seals are capable of vocal learning, and they produce vocalizations with a normal mammalian vocal tract and larynx (just like ours) and have a quite ordinary mammalian brain. (The most famous example is Hoover, a harbour seal who could speak). They are also relatively common, small (compared to humpback whales or elephants, another potential vocal learner) and very easily trained to vocalize.

Thus, pinnipeds (seals, sea lions and walruses) look like the best group of nonhuman animals to help scientists learn what’s involved in complex vocal learning at the physiological, neurological, and genetic levels. You may be surprised to know that we know very little about vocal production or vocal control in this group. This is something that my colleagues (Colleen Reichmuth at the Pinniped Lab UCSC and Terry Deacon at UC Berkeley) and I are hoping to change with our upcoming research on pinniped vocal control!

Here are the videos accompanying my paper Fitch, W. T. (2000). “The phonetic potential of nonhuman vocal tracts: Comparative cineradiographic observations of vocalizing animals,” Phonetica 57, 205-218. PDF

The key finding of this work is that animal vocal tracts are highly flexible, dynamically reconfigurable systems. This means that earlier assumptions based on anatomy of dead animals provide a poor indication of what animals can and can’t do with their vocal tracts. This has important implications for arguments about the evolution of speech. Please see the paper for details of how, why and where this was done.

In all of the mammals we have looked at, the larynx lowers during vocalization. You can see this for yourself in these videos. In the case of dogs, the larynx lowers quite considerably, down to the base of the neck, and pulls the tongue down with it. In the case of the goat the lowering is less pronounced: just enough to get the larynx down out of the nasal cavity, where it rests during resting breathing.

Barking Dog Cineradiography

Bleating Goat Cineradiography

Alligator Hiss and Grunts

Can’t see the videos? You need to download Quicktime (free) from Apple. Do it here

My colleague, mammal vocalization expert David Reby (now at the University of Sussex), and I discovered that male red deer (Cervus elaphus) have an unusual vocal adaptation: a permanently lowered larynx (previously believed to be unique to humans). This is the large lump you can see about midway down his neck. But as this video shows, during roaring stags pull the larynx down even further, to its anatomical limit at the entrance to the thorax. This makes the roar sound more impressive by lowering formant frequencies.

See: Fitch, W.T. and D. Reby, The descended larynx is not uniquely human. Proceedings of the Royal Society, Biological Sciences, 2001. 268(1477): p. 1669-1675. (available as PDF)

Many more fascinating papers on deer vocalization in this and other species are available on David Reby’s website

Dynamic Laryngeal Descent in Red Deer:

Meet “Bambo”: an adult red deer (Cervus elaphus) stag, and – during the mating season – a dangerous 200 kg of raw testosterone. This captive stag has his horns removed for the protection of the farmer who is raising him. Note the lump in the front of the neck, which is the larynx begin lowered (and try your best to ignore the penis-pumping, which does not appear to have any acoustic function):

BamboShort

This video shows the low resting position of the larynx quite clearly.

CervusRoar

Laryngeal Descent in other deer species

Wapiti (Cervus elaphus canadensis, or according to some authorities Cervus canadensis, a separate species) also lower the larynx during bugling, as shown in this video (which I made with night vision in New Zealand). You can see the larynx return to a higher position when the call finishes. Although the main portion of this call is the high-pitched bugling, at close range you can also discern formant frequencies:

(Missing)

Finally, at least some closely related species do NOT have a permanently descended larynx, like this Pere David’s stag (Elaphurus davidianus, filmed at the Scottish Deer Centre).

PereDavidCinepak

This species, apparently, has a “normal” high resting position of the larynx, and lowers it only during groaning calls.

Can’t see the videos? You need to download Quicktime (free) from Apple. Do it here

The perception and production of musical rhythm provides a number of parallels and contrasts with prosody in language. Although both metrical phonology in speech and musical rhythm instantiate a metrical “tree” of more and less accented syllables/notes, musical rhythms are typically made relative to an equally-spaced “beat” (they are isochronous). I have discussed these similarities and differences more in: BioMusic Short and BioMusic Long

My former student Andrew Rosenfeld and I have been studying rhythm perception using syncopated rhythms. Syncopation is the accenting of normally unaccented beats in music. Syncopation is very common in jazz and other African-influenced musics (e.g. salsa, much Brazilian popular music, and many others). When syncopation is strong, the underlying rhythm becomes ambiguous, and ultimately listeners are tempted to perceive the rhythm differently, “resetting” their perception of the rhythm as a less syncopated variant. Thus syncopation allows us to explore the unconscious cognitive assumptions and proclivities that the listener brings to bear when perceiving rhythm.

Using a theoretical treatement of syncopation introduced by Longuet-Higgins and Lee (1982, 1984), we developed a set of rhythms that vary considerably in syncopation, from “straight” to highly syncopated. We then ran a series of perception and production experiments to examine how subjects (Harvard students, either musicians or nonmusicians) dealt with rhythms of increasing syncopation. A preprint of the paper is available here

All the rhythms and additional supplemental material can be found here in various forms: Fitch & Rosenfeld Rhythm Files

We found, not surprisingly, that increasing syncopation makes rhythms more difficult to play and remember. Even highly skilled musicians begin to lose track of the underlying beat with the highly-syncopated rhythms, “rehearing” them as less-syncopated. The continuum of rhythms we used provides a useful tool for further exploration of the fundamental processes of rhythm – perceiving and producing a “beat”, and tracking and remembering a particular rhythmic pattern – at the edge of any particular subject’s abilities.

Examples of Syncopated and Unsyncopated Rhythmic Patterns:

References

Fitch, W. Tecumseh, and Rosenfeld, Andrew J. (2007). “Perception and production of syncopated rhythms,” Music Perception 25, 43-58. (PDF)

Longuet-Higgins, H. C., and Lee, C. S. (1982). “The perception of musical rhythms,” Perception 11, 115-128.
Longuet-Higgins, H. C., and Lee, C. S. (1984). “The rhythmic interpretation of monophonic music,” Music Perception 1, 424-441.

Darwin’s theory of language evolution revisited

W. Tecumseh Fitch

University of St Andrews

On the Occasion of Charles Darwin’s 200^th Birthday

Introduction

Darwin’s “Origin of Species” (Darwin, 1859) made little mention of human evolution.  This initial avoidance of human evolution was no oversight, but rather a carefully calculated move: Darwin was well aware of the widespread resistance his theory would meet from scientists, clergymen, and the lay public, and mention of human evolution might have generated insuperable opposition.  But Darwin’s many opponents quickly seized on the human mind, and language in particular, as a potent weapon in the battle against Darwin’s new way of thinking. Alfred Wallace, whose independent discovery of the principle of natural selection spurred Darwin into finally publishing his long-developing “outline” of the theory in 1859, didn’t help by arguing that natural selection was unable to explain the origins of the human mind.  Although Wallace had reservations about all evolutionary approaches to the mind, human language provided the most powerful argument, due to the respectable position of linguistics and philology in Victorian science.

Darwin’s most formidable foe on the linguistic front was Friederich Max Müller, professor of linguistics at Oxford University, a very well-known and well-respected scholar  (Stam, 1976).  In his “Lectures on the science of language,” delivered at the Royal Institution of Great Britain in 1861, and rapidly published thereafter (Müller, 1861), Müller launched a full frontal attack on Darwin and Darwinism, using his credentials in the “science of language” as a powerful bludgeon. Müller’s position was uncomplicated: “language is the Rubicon which divides man from beast, and no animal will ever cross it … the science of language will yet enable us to withstand the extreme theories of the Darwinians, and to draw a hard and fast line between man and brute.” For Müller, “Language” was the key feature distinguishing humans from all animals.  Müller’s arguments were seen by many as convincing: his student Noiré dubbed him “the Darwin of the mind” and considered Müller to be “the only equal, not to say superior, antagonist, who has entered the arena against Darwin” (p. 73, Noiré, 1917).  Müller’s argument about the unbridgeable, qualitative difference between human language and all forms of animal communication, combined with Wallace’s opinions, provided arguments that Darwin by necessity took very seriously.

Thus, when Darwin finally broached the subject of human evolution in 1871, in his second great book “The Descent of Man and Selection in Relation to Sex,” the need to provide a credible explanation of language evolution was a central concern (Darwin, 1871).  Darwin rose to the challenge: his “musical protolanguage” model represents a powerful marriage of comparative data, evolutionary insight, and a biological perspective on language. Darwin’s view of language was ahead of its time, and his model and arguments remain surprisingly relevant to contemporary debates.  He clearly adopted a “multicomponent” view of language, one that recognized the necessity of several distinct mechanisms to produce the complex product that we now call language, rather than privileging any one factor as the single “key” to Language in a monolithic sense.  Among these several components, he presciently recognized the necessity for complex vocal learning, and recognized that this biological capacity, while unusual among mammals, is shared with many birds.  The importance of vocal learning has often been forgotten, but also frequently reaffirmed by later scholars (Egnor & Hauser, 2004; Fitch, 2000; Janik & Slater, 1997; Marler, 1976; Nottebohm, 1976).

Darwin also adopted an empirical, data-driven approach to the problem at hand.  In particular, Darwin exploited a wide comparative database, exploiting not just his knowledge of nonhuman primate behaviour, but also insights from many other vertebrates.  Finally, and most characteristically, he resisted any special pleading about human evolution.  He intended his model of human evolution to fit within, and remain consistent with, a broader theory of evolution that applies to beetles, flowers and birds.  Unlike Wallace, who remained a human exceptionalist to his death (Wallace, 1905), Darwin aimed to uncover general principles, like sexual selection and shifts of function, to provide explanations of unusual or unique human traits.  While gradualistic, his model does not assume any simple continuity of function between nonhuman primate calls and language, and he clearly recognized the uniqueness of language in our species.  In many ways, then, Darwin’s model of language evolution finds a natural place in the landscape of contemporary debate concerning language evolution, and it is surprising that his model has received relatively little detailed consideration in the modern literature (for exceptions see Donald, 1991; Fitch, 2006).

In this essay, I aim to redress this neglect by considering Darwin’s model of language evolution in detail.  After discussing Darwin’s main points and arguments, I will briefly review additional data supporting Darwin’s model that has appeared since his death.  I will also discuss the issue of meaning, about which Darwin had too little to say, but which can be resolved by the addition of a hypothesis due to (Jespersen, 1922).  My conclusion is that, suitably modified in the light of contemporary understanding, Darwin’s model of language evolution, based on a “protolanguage” more musical than linguistic, provides one of the most convincing frameworks available for understanding language evolution. The timing of my writing, on the 150^th anniversary of the Origin, and the 200^th of Darwin’s birth, is also appropriate for a revival of interest in Darwin’s compelling and well-supported hypothesis.

Language as an “Instinct to Learn”

Chapter Two of the Descent of Man, entitled “Comparison of the mental powers of man and the lower animals” is one of the most remarkable in the entire Darwinian corpus, noteworthy for its concision and its breadth of argument, in considering the evolution of the human mind. The first half of the chapter lays the groundwork of modern research in comparative cognition, arguing that animals have emotions, attention, memory  as well as many other mental traits in common with humans.  However, Darwin’s opponents, notably Müller, had already ceded the point that animals have memory, experience emotions, and so on.  Language was the key issue, and one can imagine considerable anticipation of both pro- and anti-Darwinian readers as they turned to the section simply titled “Language”.

In ten densely-argued pages, Darwin considers some theoretical preliminaries, and then lays out his theory of language evolution.  The first stage involved a general increase in intelligence and complex mental abilities, and the second involves a sexually-selected attainment of the specific capacity for complex vocal control: singing.  The third stage was the addition of meaning to the “songs” of the second stage, which was both driven by, and in turn fueled, further increases in intelligence.

Theoretically, Darwin makes a number of important observations. First, he recognizes the crucial distinction between the language faculty (the biological capacity which enables humans to acquire language) and particular languages (like Latin or English).  The former capacity, which Darwin refers to as “an instinctive tendency to acquire an art”  (p 56), is shared by all members of the human species.  Darwin neatly bypasses the unproductive nature/nurture debate that has consumed so much scholarly energy by observing that language “is not a true instinct, as every language has to be learnt.  It differs, however, from all ordinary arts, for man has an instinctive tendency to speak, as we see in the babble of our young children” (p 55).  As ethologist Peter Marler has put it, language is not an instinct, but an “instinct to learn” whose expression entails that both biological and environmental preconditions be fulfilled. It is this “instinct to learn” for which an biological, evolutionary explanation must be sought: a thoroughly modern perspective.

Second, although he was well-aware of the peculiarities of the human vocal tract, Darwin argues that the human capacity for language must be sought in the brain, rather than the peripheral vocal tract.  He acknowledges that “articulate speech” (by which he means vocalization augmented by controlled movement of the lips and tongue, p. 59) is “peculiar to man”, but he denies that this mere power of articulation suffices to distinguish human language “for as every one knows, parrots can talk.”  Instead, Darwin states that it is not speech, but humans’ “large power of connecting definite sounds with definite ideas” that is definitive of language, and that this capacity “obviously depends on the development of the mental faculties” (p. 54). By locating the language capacity in the human brain, Darwin’s viewpoint is again thoroughly modern.

Finally, Darwin recognized the relevance to language evolution of birdsong, which he considered the “nearest analogy to language”.  Like humans, birds have fully instinctive calls, and an instinct to sing.  But the songs themselves are learned.  He recognized the parallel between infant babbling and songbird “subsong”, and recognized the key fact that cultural transmission ensures the formation of regional dialects in both birdsong and speech.  Finally, he recognizes that physiology is not enough for learned song: crows have a syrinx as complex as a nightingale’s but use it only in unmusical croaking.  All of these parallels have been amply confirmed, and further explored, by modern researchers (Doupe & Kuhl, 1999; Marler, 1970; Nottebohm, 1972, 1975).

Darwin’s “Musical Protolanguage” Hypothesis

Darwin’s model of the phylogenesis of the language faculty, like most models today, posits that different aspects of language were acquired sequentially, in a particular order, and under the influence of distinguishable selection pressures. The hypothetical systems characterized by each addition can be termed, following (Bickerton, 1990; Hewes, 1973) “protolanguages”.  Darwin’s first hypothetical stage in the procession from an ape-like ancestor to modern humans was a greater development of proto-human cognition: “The mental powers in some early progenitor of man must have been more highly developed than in any existing ape, before even the most imperfect form of speech could have come into use” (p 57).  He elsewhere suggests that both social and technological factors may have driven this increase in cognitive power.

Next, Darwin outlines the crucial second step: what I have dubbed “musical protolanguage” (Fitch, 2006).  Having noted multiple similarities with birdsong, he argues that the evolution of a key aspect of spoken language, vocal imitation, was driven by sexual selection, and used largely “in producing true musical cadences, that is in singing”.  He suggests that this musical proto-language would have been used  in both courtship and territoriality (as a “challenge to rivals”), as well as in the expression of emotions like love, jealousy, and triumph. Darwin concludes “from a widely-spread analogy” (amply documented with comparative data later in the book) that sexual selection played a crucial role driving this stage of language evolution, in particular suggesting that the capacity to imitate vocally evolved analogously in humans and songbirds.

The crucial remaining question is how emotionally-expressive musical proto-language made the transition to true meaningful language — how, in Humboldt’s words, humans became “a singing creature, only associating thoughts with the tones” (p. 76, von Humboldt, 1836).  This leap, from non-propositional song to propositionally-meaningful speech, remains the greatest explanatory challenge for all musical protolanguage theories (cf. Mithen, 2005). Darwin, citing the previous writings of Müller and (Farrar, 1870), suggests that articulate language “owes its origins to the imitation and modification, aided by signs and gestures, of various natural sounds, the voices of other animals, and man’s own instinctive cries”.  Darwin thus embraces all three of the major leading theories of word origins of his contemporaries (cf. Fitch, in press).  Once proto-humans had the capacity to imitate vocally, and to combine such signals with meanings, virtually any source of word forms and meanings would suffice, including onomatopoeia (an imitated roar for “lion”, or “whoosh” for wind), and controlled imitation of human emotional vocalizations (mock laughter for “play” or “happiness”).  The attachment of specific and flexible meanings to vocalizations required only that “some unusually wise ape-like animal should have thought of imitating the growl of a beast of prey … And this would have been a first step in the formation of a language”.

Darwin does not suggest that the evolutionary process would stop with the initial acquisition of meaning.  For “as the voice was used more and more, the vocal organs would have been strengthened and perfected”.  Additionally, language would have “reacted on the mind by enabling and encouraging it to carry on long trains of thought” which “can no more be carried on without the aid of words, whether spoken or silent, than a long calculation without the use of figures or algebra”.  Thus began the interactive evolutionary spiral that led to modern humans.

Signalling Modality: Vocalization or Gesture?

Darwin also explicitly acknowledged the role of gesture in conveying meaning, echoing Condillac’s earlier arguments (Condillac, 1971 (1747)) and presaging contemporary discussions (Arbib, 2005; Corballis, 2003; Hewes, 1973; Stokoe, 1974; Tomasello & Call, 2007).  Darwin was aware of the power of signed language: he reminds us that using his fingers “a person with practice can report to a deaf man every word of a speech rapidly delivered at a public meeting” (p 58).  He also acknowledged the value of gesture in conveying meaning, and allowed that vocal communication would have been “aided by signs and gestures” (p. 56).  Nevertheless, he argues against gestural theorists, because the pre-existence in all mammals of “vocal organs, constructed on the same general plan as ours” would lead any further development of communication to target the vocal organs rather than the fingers.

Darwin clearly believes that the power of speech is neural, not peripheral, citing the early aphasia literature as a demonstration of “the intimate connection between the brain, as it is now developed in us, and the faculty of speech”.  Comparing the vocal organs and brain, he concludes “that the development of the brain has no doubt been far more important”.   And although he uses a continuity argument to support the early and sustained role of speech, he firmly acknowledges the abrupt modern discontinuity in the linguistic system that has thus evolved.  Thus, like many other insightful commentators (e.g., Donald, 1991; Hockett & Ascher, 1964), Darwin recognized that posing phylogenetic continuity and modern discontinuity as in any way opposed is to create a false dichotomy.  The tree-like nature of phylogeny guarantees that both are core parts of the evolutionary process.

Darwin Redux: Modern Comparative Data

Summarizing, Darwin suggested that the first step on the road to human language was a general increase in intelligence in the hominid lineage.  In a typically pluralistic fashion, he recognized both “social intelligence” (“Machiavellian intelligence” in the modern trope (Byrne & Whiten, 1988)) and technological/ecological intelligence (e.g. for tool use) as playing important selective roles.  Given our modern understanding of hominid evolution, this first stage might be provisionally linked to the genus Australopithecus or perhaps early Homo (e.g. Homo habilis).

The second stage is the least intuitive: that before vocalizations were used meaningfully they were used, so to speak, aesthetically, to fulfil many of the same functions that modern humans use music today (courtship, bonding, territorial advertisement and defense, competitive displays, etc.).  This idea that complex vocalizations (and thus some aspects of phonology and syntax) might have preceded the ability of speech to convey propositions and distinct meanings is the most challenging aspect of Darwin’s model.  But Darwin uses the comparative database, and particularly detailed analogy between learned bird song and human song and speech, to show that this step is not just plausible but well-documented: it has occurred in many other species.  Indeed, modern data shows that vocal learning, without propositional meaning, has evolved independently in at least three other clades of mammals (cetaceans, pinnipeds and bats) and three clades of birds (parrots, hummingbirds and oscine songbirds) (Janik & Slater, 1997; Jarvis, 2004).  Such convergent evolution, or repeated independent evolutionary developments of a comparable ability, provides our strongest empirical basis for estimating the likelihood of a particular type of evolutionary event (Harvey & Pagel, 1991).  Much subsequent research affirms, and extends, the observations of parallels between language learning and birdsong that Darwin offered in 1871.  Thus, whether intuitive or not, Darwin’s focus on, and hypothesis for, the evolution of vocal learning is consistent with a wealth of evolutionary and comparative data.

Difficulties with Darwin’s Model: Evolving Phrasal Semantics

“How did man become, as Humboldt somewhere defined him, ‘a singing creature, only associating thoughts with the tones’?” Otto Jespersen 1922 (p. 437)

Despite its many virtues, there remain some important problems with Darwin’s model that have impeded its acceptance today.  The first and most important is his explanation of the addition of meaning.  Darwin’s explanation, as typical for his day, was concerned only with word meanings (what today would be termed “lexical semantics”).  But from the viewpoint of modern linguistics, his model seems wholly inadequate to deal with large swaths of semantics, particularly those aspects tied in with the interpretation of whole phrases and sentences (“phrasal semantics”).  Modern formal semantics has developed rigorous models of this aspect of linguistic meaning (Dowty, Wall, & Peters, 1981; Guttenplan, 1986; Montague, 1974; Portner, 2005), and it is far more complex and difficult to explain than lexical semantics.  Although one can hardly blame Darwin for not foreseeing these relatively recent developments in linguistics, they nonetheless raise substantial difficulties for his model.  For much of the syntactic “glue” which binds sentences together into large, meaningful wholes (function words, inflection, bound morphemes, word order, and a host of others) cannot be understood as resulting from onamatopoeia or imitation of emotional expressions.  Nor can they be readily understood as “inventions” of some uniquely intelligent individual: all evidence suggests that these indispensable linguistic tools develop reliably in individuals of normal intelligence (Bickerton, 1981; Kegl, 2002; Mufwene, 2001; Mühlhäusler, 1997; Senghas, Kita, & Özyürek, 2005).  This key aspect of language thus seems to have a biological basis.  Darwin does recognize the phenomenon today called “grammaticalization”: he states that “conjugations, declensions, &c., originally existed as distinct words, since joined together” (p 61).  But he offers no model for the origin of these distinct words, and it is hard to see how onamotopoeia or similar processes could have generated this original syntactic and semantic “glue”.  Thus, complex phrasal semantics remains unexplained by Darwin’s model.

However, this oversight was remedied long ago by the linguist Otto Jespersen (Jespersen, 1922). Jespersen’s basic insight involves recognizing the link, in humans, between musical and linguistic phrases, and working conceptually backward from there.  Jespersen suggested a form of protolanguage in which, initially, whole propositional meanings attached to entire sung phrases, but where there was no consistent link between the individual conceptual components of the meaning, and component parts of the musical phrases (syllables and notes).  Thus, there were no “words” as we now understand them.  From this “holistic” starting point, Jespersen argued that a cognitive process of analysis started, which slowly isolated individual chunks of the musical phrase (syllables, or multi-syllabic “phraselets” — what today we call “words”) and associated them with individual components of the meaning (e.g. nouns, verbs and adjectives, whose precursors were already present in the conceptual systems of our pre-linguistic ancestors).

Jespersen’s hypothesis of a “holistic protolanguage” has recently been rediscovered and championed by linguist Alison Wray (Wray, 1998, 2000) and neuroscientist Michael Arbib (Arbib, 2005).  Both cite considerable additional evidence supporting this “analytic” model, including data from modern adult language, child language acquisition, and cognitive neuroscience.  Supporters of the more intuitive “synthetic” model of protolanguage, in which words evolved first followed by syntactic operations for combining them (e.g., Bickerton, 1990), have subjected holistic models to extensive criticisms (Bickerton, 2007; Tallerman, 2007, 2008).  However, I argue that most of these critiques miss their mark if the notion of a musical protolanguage is accepted as a starting point (cf. Fitch, in press).  Jespersen/Wray’s model of holistic protolanguage thus dovetails nicely with the musical protolanguage hypothesis, in ways that I believe resolve many, if not all, of these criticisms (cf. Fitch, 2006; Mithen, 2005).

Sexual Selection:

A second problem with Darwin’s model remains unresolved at present: his focus on sexual selection as the force driving the evolution of musical protolanguage.  Appearing as it did as a few pages of an extensive tome introducing and then extensively documenting the very idea of sexual selection, this aspect of Darwin’s theory has the virtue of explaining a core aspect of human evolution using a broad principle abundantly demonstrated in the evolution of other species.  As throughout his work, Darwin eschewed “special pleading” for our own species.  The central difficulty for this beautiful hypothesis is posed by two ugly facts about modern human language: it is equally developed in males and females, and is expressed very early in ontogeny, essentially at birth (Fitch, 2005a). These aspects of language differentiate it sharply from most sexually-selected traits, which are strongly biased to develop in the more competitive sex (typically males), and only at sexual maturity.  If anything, human females have superior language skills when compared to men (Henton, 1992; Kimura, 1983; Maccoby & Jacklin, 1974), and language is remarkable in its very early development, with at least some early tuning to phonology already occurring in utero before birth (DeCasper & Fifer, 1980; Mehler et al., 1988; Spence & Freeman, 1996).

There are several potential answers to the difficulty that these facts pose: one is to argue that during the musical protolanguage stage, sexual selection was the driving force, and song was (as in most bird species) expressed mainly in males at sexual maturity.  Then, at a later stage (presumably during the evolution of meaningful language) some other selective force kicked in, so that language became equally (or better) expressed in females, and was pushed to develop early.  A candidate selective force is kin communication: that selection for information transmission between parents and their offspring, or more generally between adults and their younger kin.  I have suggested that kin selection drove this second stage of the evolution of propositional semantic content (Fitch, 2004, 2007). For an exploration and critique of this idea, see (Zawidzki, 2006).  This kin-selection scenario neatly explains the early ontogenetic appearance of language in infants (the earlier offspring begin absorbing their elders’ knowledge, the better), and its bias towards females (who are primary caregivers in all hominoids).  The continued presence of meaningful speech in males is easily explained by the dual facts that immature males must also learn, and that, unusually in humans, adult males play an important role in child rearing (whether the father, or male siblings of the mother, is irrelevant to this fact).  Finally, this kin-selection model has the virtue of explaining why language evolved in humans and not in other “musical” lineages.  Humans combine an extended childhood, with ample time to acquire knowledge, with very small reproductive output.  The fact that ape babies are born singly, and rarely, conspire to make the survival of each individual hominid infant a crucial component of reproductive success in the great ape lineage (cf. Fitch, 2007; Hrdy, 1999, 2004).

An alternative possibility is that sexual selection was, and remains, an important driving force in human cognitive evolution, including language (Miller, 2001), but that human pair-bonding has “changed the rules” in significant ways, so that both sexes are choosy, and both compete for high-quality mates.  Some comparative data can be cited in support of this second option.  Recent data shows that female bird song is not so uncommon as thought by Darwin, who considered female song to be a simple aberration (Langmore, 2000; Riebel, 2003; Ritchison, 1986). There is some evidence suggesting that sexual selection can indeed drive female bird song, though it seems clear that female song is a secondary derivation of male song in most lineages (Langmore, 1996).  While these observations provide some support for the idea that the dual-sex expression of human language could result from sexual selection, it is important to recognize that female song still appears to be numerically speaking exceptional and that any model based on sexual selection will have difficulty explaining the extremely early development, and productive use, of language in human infants.

A final possibility is that sexual selection never played a role in the evolution of music or of language.  The popular notion that music evolved for courtship (Miller, 2000, 2001) stands on a surprisingly weak empirical footing compared to a less obvious, but better-documented function of music: mother-infant communication (Trainor, 1996; Trehub, 2003a, 2003b).  Mothers sing to their infants all over the world, even those who claim to be unable to sing (Street, Young, Tafuri, & Ilari, 2003), and infants both prefer song to speech, and respond to song in manifestly adaptive ways (e.g. engaging with and getting excited by play songs, and being lulled to sleep by lullabies (Trehub & Trainor, 1998).  These observations suggest that music originally functioned in a childcare context, as it continues to do today.  By this model, the use of music in bonding among adults is simply a side-effect of this central function, and its occasional use in courtship is a red herring (Dissanayake, 2000; Falk, 2004; Trehub & Trainor, 1998).  This final possibility is clearly compatible with the kin-selection arguments advanced above, but here there would be no intervening stage of language evolution in which sexual selection ever played a dominating role.  Even Darwin was occasionally wrong.

Terminological Niceties:  Musical or Prosodic Protolanguage?

A final, less crucial difficulty with Darwin’s model is terminological.  Darwin himself seemed to conceive of his pre-semantic protolangage in terms directly comparable to modern day music (or at least he provides no indication that this is not the case).  He concludes that “musical notes and rhythm” were present in this protolanguage, and that they were deployed  ”in producing true musical cadences, that is in singing.” This is why I term his model “musical protolanguage”.  However, modern human music consists not just of song, but also instrumental music, so this appellation might immediately have connotations of drumming, whistling or flutes that are not, strictly speaking, relevant to language evolution.  More pertinently, if we take the musical protolanguage model seriously, we must acknowledge that modern music may not necessarily preserve the state of this protolanguage precisely, and that both music and language have changed in the interim (cf. Brown, 2000).  That is, Darwin’s hypothetical communication system was proto-music, not music per se.  Adopting the logic of comparative reconstruction, we can then ask which aspects of modern speech, and of song, are shared, and thereby reconstruct this system (Fitch, 2005b).  The central shared aspects are prosodic and phonological: the use of a set of primitives (syllables) to produce larger, hierarchically-structured units (phrases) which are discretely distinctive.  But two key “musical” aspects are not shared between speech and song: namely discrete-pitched notes, and temporal isochrony (a steady beat).  I have used this comparison of modern speech and song to argue for a subtly different model from that of Darwin, which I termed “prosodic” rather than “musical” protolanguage, in which protolanguage consisted of sung syllables, but not of notes that could be arranged in a scale, nor produced with a steady rhythm (Fitch, 2006).  This prosodic protolanguage model thus includes the “sung cadence” aspect of Darwin’s model, while rejecting both his “notes” and “rhythm” (at least as normally construed).  Both of these aspects of (most) modern song are, by hypothesis, more recent developments in music not present in protolanguage.  I see this as an adjustment of Darwin’s hypothesis, fully in keeping with its spirit.  Furthermore, it is unclear from his writings whether Darwin would have disagreed with this adjustment.

A different reconstruction of the common ancestor of music and language, involving both discrete pitches and isochronic rhythm (as well as tone-based meaning) is given in (Brown, 2000).  Brown also argues that his hypothetical protolanguage, which he dubs “musilanguage” could not have evolved by normal neo-Darwinian selection and thus demands a group selection explanation.  This remains its clearest, and most dubious, distinction from what is otherwise just a rediscovery of Darwin’s basic hypothesis (for critiques see Botha, 2008; Fitch, in press).

Conclusions

I have argued that Darwin’s model for language evolution, “musical protolanguage,” suitably updated, provides a compelling fit to both the phenomenology of modern music and language, and to a wealth of comparative data.  By placing vocal control at the centre of his model, Darwin availed himself of the rich comparative database of other species who have independently evolved complex vocal imitation, and he thus explains two of the features of human language that set if off most sharply from nonhuman primate communication systems: vocal learning and cultural transmission.  The biggest missing piece in Darwin’s model, as I see it, is a reasonable explanation of phrasal semantics (and the aspects of syntax that go with it), but this gap was filled by Jespersen by 1922.  Together, these hypotheses provide one of the leading models of language evolution available today (for an enthusiastic book-length exploration seeMithen, 2005), and one that has been repeatedly re-discovered by later scholars (e.g., Brown, 2000; Livingstone, 1973; Richman, 1993).  While many aspects of what has now become a family of models remain to be explored empirically (the issues surrounding sexual, kin and group-selection remain particularly unclear), this is a model worthy of detailed consideration and elaboration today. Most importantly, Darwin’s model makes numerous testable empirical predictions (for example about the partially overlapping nature of the brain mechanisms underlying music and spoken language, and their genetic basis) that can be answered in the coming decades.

This year of Charles Darwin’s 200^th birthday seems an opportune time for Darwin’ own model of language evolution to regain the prominence it deserves.

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