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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)
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