Transcript What is co-evolution? - University of Connecticut

Universal Darwinism?
• We know that biological evolution requires
replication with variation, plus natural
selection for useful traits
• But Dawkins suggests that evolution will
ALWAYS happen when these
preconditions are met
• This evolution might not be biological!
Breeding ideas?
• It may seem silly to think of an idea, or a
form of behaviour, breeding…
– BUT breeding = creating a new copy
– Whenever an idea is spread to another mind,
a new copy of the information in that idea is
created
• … so we can say that whenever someone
hears a new idea or learns a new behaviour,
that idea has successfully reproduced
How do ideas reproduce?
• Imitation
– Animals very bad at this
– Humans very good at this
• We readily imitate the behaviours of others
– Linguistic behaviours
– Fashions, hobbies, crazes
The evolution of culture
• So ideas reproduce (with variation) …
– Are ideas selected?
– Yes!
• What ideas will get selected?
– i.e. What ideas will tend to spread?
– Ideas which are good at spreading themselves!
Enter the meme
• Dawkins in The Selfish Gene:
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“meme” as the unit of imitation
(just as “gene” is the unit of biological inheritance)
suggested that memes can evolve
groups of memes making up “idea animals”
• Theory elaborated by Blackmore (1999) and
others (e.g. the philosopher Dennett)
• Key point: memes are selected for their
usefulness to themselves, not to us!
• Memes as parasites?
What is co-evolution?
• As we have seen, species evolve by natural
selection to fit their environment…
• … but part of that environment may be
other organisms!
• Organisms can evolve to become
dependent on one another (symbiosis)
Co-evolution in nature
• Intestinal bacteria
• Insects pollinating flowers
• The eukaryotic cell
• … and many other examples
Co-evolution can also occur in situations where one
organism is parasitic on another
• bacteria specialize to invade other species, which
in turn evolve defenses
• consider case of malaria, which may account for
the persistence of the sickle-cell gene in some
human populations
We might also consider co-evolution of different
genes, at separate loci, within a single species
• For example, consider the stick insect, where
genes that lead to the development of a body
appearance that resembles a twig co-evolve with
genes that lead to behavior that reinforces the
camouflage
Language as co-evolution
Deacon and Blackmore
In this case we will consider co-evolution between genes
and memes within a single species, rather than coevolution between two species
What has this got to do with language?
• If we put these two ideas together…
• … we can see language as a bundle of
behaviours, an “idea animal”
– Its habitat is the human brain
– It has evolved to fit that habitat
• Can we explain the origin and / or
acquisition of language in these terms?
Blackmore (1999)
• Blackmore on the Big Brain: it evolved to
allow us to store and spread memes better
• Blackmore on the origin of language:
– What is language for? – she concludes it is
for spreading memes
• Co-evolution:
– language (made of memes) is evolving…
– But our genes are evolving to fit our memes
(inc. language) too
Deacon (1997)
• Deacon: key to language is symbol use
– Control of social/sexual relationships
• Language evolves to fit its environment
– Its environment is the brain of the child
• Language has therefore evolved to become
easy for a child to learn
– Deacon: this explains language acquisition
• Our brains have also evolved to
accommodate language (co-evolution)
Summary
• Two theories based on language evolving to
inhabit us, rather than us evolving to use
language
– Blackmore: meme theory
– Deacon: language evolving to fit child’s brain
• Both theories involve co-evolution
– Language and brain/body have evolved
together, becoming co-dependent/symbiotic
Word of warning
• Both Deacon and Blackmore’s theories are
relatively new…
– … and fairly controversial
• They are only favoured by a minority of
linguists
• e.g. the Chomskyans oppose this view