Evolution of Human Language

Carissa Fletcher2.4.2012

Contents

• Define language and its components• Relationship to social learning• Theories on how language evolved• Empirical evidence from NHP research• Evidence from genetics and the fossil record

Definition of Language

“language can be defined as the bidirectional system that permits the expression of arbitrary thoughts as signals and the reverse interpretation of those thoughts” Fitch, Huber and Bugnyar (2010)

Who has language?

Animals have communication systems that allow some biologically important information concepts or emotions to be expressed vocally or visually.

However, humans are unique in possessing a system which allows any concept to be expressed and understood.

Components of human language in the broad sense

Syntax Semantics

Phonology Pragmatics

Large memory

Human Language as an emergent

property

Fitch 2010

DefinitionsTerm Components Nature

Syntax - Word stems, affixes- Phrases, sentences- Rule governing combinations- Hierarchical (

- Recursive/self embedding

Computational. Structure generating mechanisms that map between signals and concepts.

Phonology - Phonemes (fricatives, nasals, plosives m, p, b, f,v)

- Arranged hierarchically into syllables- Intonation, stress, prosody, rhythm- Double articulation

Physical. Perceptual and motor systems underlying speech. Also, the process of learning requires close imitation.

Semantics - Meaning in the language Philosophical. Central cognitive mechanism supporting concept formation and expression

Pragmatics -What the speaker intends- Mittelungsbedurfnis- (Shared attention system, Theory of

Mind mechanism

Psychological. Requires an ability to infer intentions of a signaller which can be based on indirect cues such as ‘gaze direction’. Also, sharing inner thoughts relies on an understanding of the thoughts of another (ToM)

Language – its relationship to social cognition and culture

Advanced social cognition is required for children to acquire language as sophisticated “mind reading” abilities needed to deduce word meanings and to communicate pragmatically. Once in place language itself becomes a tool for social cognition becomes central to Human Culture.

Language diversity

- Over 6000+ different languages globally- Darwin saw

similarities between the evolution of species and the evolution of languages.

Grey et al. 2010 NeighborNet analyses of the Indo-European linguistic items

Theories on how language evolved?

1. Innate biological system - System of cognitive structures develop and

are genetically determined. - There are some shared computational

commonalities between all languages e.g. Universal Grammar

(Chomsky 2007)

- language syntax shows evidence of complex design – similar to, for example, the visual system. “biological adaptation is the only way to explain the appearance of such design”.

(Pinker 2003; Nowak 2001)

2. Usage based system:- Human language is symbolic- We evolved cognitive skills enabling the use of

symbols - 'social-cognitive' and 'social-motivational'

infrastructure needs to be in place before language could arise in humans.

- Human communication is a fundamentally cooperative enterprise that could not have arisen without the shared intentionality.

- Shared intentionality allows for the emergence of naturally intention directing gestures (pointing and miming) Tomasello (2008)

2. Usage based system:- The close relationship between

manual gesture and vocalization(in the form of speech via mirror neurons Corballis (2003)

- Cooperative hunting, food savaging and food sharing have been powerful drivers of the information sharing capacity embodied in language.

- Bickerton (2010) suggested that the capacity of displacement in human language

Comparative approach

1. Shared vs Unique?

2. Gradual or non-gradual evolution of this feature?

3. Continuity or exaptation?

Fitch 2010

Vocal Production in Primates- NHP calls develop under

strong genetic influences (Hammerschmidt and Fischer 2008)

- Vocal plasticity in NHP the form of acoustic convergence at the group level has now been well documented.

- Mouse lemurs; Hafen et al. 1999,

- Japanese macaques,- Chimpanzees (Tanaka 2006)

- Marmosets (Snowdon 1999),

- Campbell's monkeys (Lammasson 2004; Ouattara 2009

- high degrees of social affinity also produced acoustically more similar calls independent of genetic relatedness (Lemasson 2011).

? neural circuits involved in the generation of vocal calls in NHP are radically different from those involved in human speech (Jürgens, 2002).

~ 63Mya

Mouse lemur

Language affixation

Cotton Top Tamerins can learn an affixation pattern that shares important information with our own inflectional morphology

e.g. the rule that adds ‘-ed’ to create the past tense (Endress et al. 2009)

Method‘shoy’ = affix‘bi’, ‘ka’, ‘na’, ‘to’, ‘gu’ ,‘lo’, ‘ri’ and ‘nu’ = familiar stems‘brain’, ‘breast’, ‘wasp’, ‘snake’ and ‘swan’ = test stems

1. Familiarised subjects to bisyllabic items conforming to either a pre-fixation or suffixation pattern they heard 14 words 70 times.

2. TEST ‘shoy’- ‘bi’ or TEST ‘ka’- ‘shoy’

a. Half the subjects tested on the pre-fixation pattern and 29 days later the suffixation pattern

b. The other half tested suffixation pattern first and 33 days later the pre-fixation pattern

Results

The monkeys orientated more towards violations that consistent conditions

Cotton Top Tamerins can learn a rule formally similar to affixation patterns in humans

-suggest that this domain specific mechanism shared across humans and NHP

Combinatorial signals

Putty nose monkey

Arnold and Zuberbuhler 2004

Human speech uses a rule-governed assemblage of morphemes into more complex vocal expressions.

Loud alarm calls

Hack= Pyows =

Pyow-Hack = ‘Group progression’

Playback experiments

Supporting theories

Innate Biological System

Evidence from gestures

Association of manual and facial/vocal signals in groups of chimpanzees and bonobos, - 31 manual gestures - 18 facial/vocal signals.

• Gestures seem less closely tied to particular emotions, such as aggression or affiliation,

• possess a more adaptable function and likely under greater cortical control than facial/ vocal signals • Candidate modality to have acquired

symbolic meaning in early hominins?

Symbolic language• Washoe was taught over 100

manual signs,3 based loosely on American Sign Language (ASL)

• Combine signs into two- or three-‘‘word” sequences to make simple requests (Gardner & Gardner, 1969).

Kanzi –large vocabulary, based on pointing to symbols on a keyboard + gestures-limited to only two or three ‘‘words”. -follow instructions conveyed in spoken sentences with as many as seven or eight words (Savage-Rumbaugh, Shanker, & Taylor, 1998).

-roughly equivalent to that of a 2½-year-old girl (Savage-Rumbaugh et al., 1998)

Supporting theories

Usage based system

Genetics

-KE family show no activation in Broca’s area while covertly generating verbs (Liégeois et al., 2003). Point mutation in FOXP2

-FOXP2 gene in humans is involved in the cooption of vocal control by Broca’s area (Corballis,2004a).

-Highly conserved in mammals, FOXP2 gene underwent two mutations since the split between hominid and chimpanzee lines.

- ‘‘some 10,000–100,000 years ago” (Enard et al., 2002) it not unreasonable to suppose that it coincided with the emergence of Homo sapiens around 170,000 years ago.

-Recent evidence that the mutation is also present in the DNA of a 45,000-year-old Neandertal fossil, suggesting that is goes back at least 300,000– 400,000 years to the common ancestor of humans and Neandertals (Krause et al., 2007).

KE family

Fossil Record-Fossil evidence suggests that the anatomical requirements for fully articulate speech were probably not complete until the emergence of H. sapiens.

e.g. hypoglossal nerve (see image), which passes through this canal and innervates the tongue, passes through the hypoglossal canal, and this canal is much larger in humans than in great apes, probably because of the important role of the tongue in speech.

- Fossil evidence suggests that the size of the hypoglossal canal in early australopithecines, and Homo habilis, was within the range of that in modern great apes,

- the Neanderthal and early H. sapiens skulls was contained well within the modern human range (Kay, Cartmill, & Barlow, 1998)

Summary• Define language and its components• Relationship to social learning• Theories on how language evolved• Empirical evidence from NHP research• Evidence from genetics and the fossil record