Evolution of Speech and Language Flashcards
Why do people think we shouldn’t study the evolution of speech?
Very risky, it has only evolved in one way - in our species
usually we study a comparative trait, but we can’t do this as it hasn’t evolved in other species
What happened in 1866?
The linguistic society banned all discussions on this topic because it wasn’t scientific
however, a interdisciplinary approach (combines different methods) can yield a possible scenario
What are the controversies about language evolution?
Chomsky/gould - language couldn’t have evolved through natural selection, but as a by product of selection for other abilities or as a consequence of as yet unknown laws of growth and form
Pinker - natural selection is more than sufficient to explain the evolution of language, no different from echolocation or stereopsis - the language organ is no different to the vertebrate eye, elephant trunk, only explained by natural selection
Why does Chomsky believe that evolution hasn’t evolved through natural selection?
Not enough genetic variation - either can speak or not
Confers no selective advantage - at an individual level
Would require more evolutionary time and genomic space than is available
What does language require?
A range of central/peripheral specialisations - not all necessarily evolved to specifically have a function as language and speech
What does pre adaptation / exaptation mean?
When a trait or a feature has a function which is unrelated to the reasons for its origination - language may have evolved at a certain stage in our evolution when key innovations had already evolved for other functions
What are the previous claims of uniqueness?
Fast mapping, categorical perception, descended larynx.. these are wrong
What is human evolution?
We have evolved from our common ancestor or modern apes and humans that lived 6-7 million years ago
When did we evolve?
6-7 million years ago
What makes humans unique?
Our ability to walk upright, on their legs only: bipedalism
What does language require?
Ability to memorise large numbers of symbolbs
large amount of cognitive memory
syntactic, recursive thought; ability to organise and embedded series of ideas
ability to learn via imitation
What does speech require?
ability to plan, produce and perceive flow of sounds
sophisticated control of articulators and breathing
a vocal apparatus capable of produce a large variety of sounds
How much information does our brain need to store?
The neocortex of the human brain must be able to store lots of information acquired through learning:
vocal (10,000-1000,000 words)
grammar
multiple ways that can be said and cannot be said
What is increase in brain size essential for?
The emergence of language in human communication
When did hominids acquire a large brain?
Brain size is not larger than expected from their body size
It began to increase relative to body size with genus Homo, 2 million years ago
What are the costs of having a large brain size?
It is only 2% of our body weight but consumed 20% of our energy
Human babies are born premature, pregnancy should last 17 months
but there are selective advantages to make it worth while
Why is the brain so large?
To enable language/social cognition
3 hypothesis - machiavellian intelligence hypothesis, social contract hypothesis and the Scheherazade effect
For other reasons, hunting, fishing
Machiavallian intelligence or social brain hypothesis
Evolution of increased brain size is a result of selective pressures favouring individuals capable of ealing with increasingly complex social relationships (as social group size increased)
problem: they could live in a large group because of large brain or vice versa
The social contract hypothesis
A large brain and language has evolved to facilitate symbolism
symbolism is necessary to enable the coordination of complex social contracts (marriage) rendered necessary by hunting
need language to understand each other
The Scheherazade effect
Verbal skils have evolved as an indicator of gene quality - selection for by sexual selection
What does the prefrontal lobe play a role in?
Critical role in planning and decision making, two abilities that are central to speech - speech is made of linear sequence of symbols that require a speaker to plan ahead to decide what to say and how to say it - planning suppresses freedom
What did people believe about the prefrontal lobe?
That is was more developed relatively to other neocortical areas when compared to other non human primates
Why is the idea about the prefrontal lobe being larger not correct?
Recent studies using MRI have showed that the human frontal lobe is not relatively larger than those of other apes
What do mirror neurons do?
Neurobiologists have discovered neurons in monkey’s brains that fire both:
when the animal performs a particular movement and when it observes another animal performing this movement
Where are mirror neurons located in?
Located in both hemispheres in the area F5 of the premotor cortex, the homologue of Broca’s
What do the mirror neurons do?
Enable mapping of perception onto execution - provide a starting point for the evolution of imitation abilities required for the evolution of language
Where are the differences in cortical-laryngeal neurons in non human mammals and humans?
Nonhuman mammals - they have no direct connection to the neurons that control the muscle of the tongue and larynx
Humans have direct connections to the laryngeal motor neurons that control the muscles of the larynx
What does Broca’s area play role in?
The production of speech
What does Wernicke’s area play a role in?
The perception of speech
Broca and Wernicke’s area in the past
They were differentiated in Homo Habilis as early as 2 million years ago
What does speech require?
Sophisticated control of breathing - breathing without voicing uses the diaphragm is controlled by the vagus nerve
How do your control the intonation / speech of breathing?
The air pressure in the trachea, just below the larynx must remain constant regardless of how full the lungs are
How to achieve complex control of the air pressure in the trachea?
Use the muscles of the thorax and the abdomen, which are controlled by the thoracic region of the spinal cord - thoracic breathing
What is the thoracic vertebral canal in humans?
Larger in modern humans than in other primates and in our ancestors
Why were early humans not capable of speech?
Because they weren’t able to control their breathing
Why may breathing have evolved?
To enable control of breathing during running or swimming
What does the two tube vocal tract do?
Allows you produce a full range of vowels that compose human speech
Do apes have a pharynx?
No, so they are limited in the range of sounds that they can produce so can’t provide human speech sounds
Why did the human larynx descend?
To enable speech
What is the size exaggeration hypothesis?
Some species that don’t have speech and language, still have a lower larynx but this is because of their lower formants - sound bigger, scale other males, have a sexual selection
the descent of the larynx in human could be analogies to the descent in red deer, it could have served a sexually selected function and later exalted to help human speech
Could neanderthal speak?
The larynx was probably descended but his oral cavity was so long that the larynx would have had to be located in the thoracic cavity in order for its vocal tract to be composed of two tubes of equal length - could probably speak, but had a limited range of sounds - couldn’t produce i and a
Did gestural communication predate speech?
Gesture is predominant in primates
apes perform dyadic gestural interactions but very few dyadic vocal interactions - language trained apes are better at sign language then speech
What happened as they stood up 5-6 million years ago?
They stopped using hands for walking, so their hands and arms were freed, enabling more effective gesturing
What are complex gestures associated with?
Food manipulation
aimed throwing
tool making and use
Why are we right handed?
We are the only species that are right handed - dominance of left hemisphere
most vertebrates show left hemisphere dominance for vocal production and perception
but no left hemisphere dance for gestures in non humans
Why has right handedness arisen?
Because of a long lasting association between gestures and vocalisations during he evolution of language
What has gestural communication played a role in?
The evolution of speech
the discovery of mirror neurons supports the idea that imitation ability essential to language may have involved gestural communication before vocal
When were vocalisations added to communication?
Accompanying gesture
What did the first spoken words come from?
ding dong theory - imitation of nature sounds
pooh-pooh theory - imitation of internal states bow-wow theory - imitation of other species calls
When did vocal communication become more important?
When the vocal apparatus and control became more sophisticated
What advantages does speech have over gestures?
Frees the hands - can do something else
Works in the dark
Not directional - talk to someone behind you
High information flow
When was speech discovered?
50,000 years ago and is culturally transmitted
Why couldn’t they speak 160,000 years ago?
They may have been biologically ready for speech with a modern brain and vocal apparatus but a fully efficient speech may only have been invited 50,000 yeas ago
What is protolanguage?
Ability to form representations and form them into short sentences
A possible scenario for language evolution
Lifestyle and tools of early humans - no more than a protolanguage consisting of mainly gestures
homohabilis - good vocal control led to inclusion of vocal components
homosapiens - once a modern brain and vocal tract, speech became more efficient
