Download Linguistics 001, Fall 2004 - University of Pennsylvania

Linguistics 001, Spring 2010
Evolution of Language: Prospects
Outline
• In the study of biological systems,
interesting questions often center on
evolution; i.e., on how it is that things
came to be as they are
• The same type of reasoning has been
applied to (aspects of) cognition, and in
particular to the development of
language as a human ability
Prospects
• The reading from the bulkpack, by Lewontin,
advances a number of arguments to the
effect that studying the evolution of cognition
(and language) is at best a kind of ‘storytelling’
• In order to understand the force of these
objections, which we review below, we will
first examine what evolutionary thinking might
tell us
Possibilities
• Researchers focussing on arguments
that language is a product of evolution
(e.g. Pinker and Bloom) try to justify this
claim in various ways:
– Language is a complex adaptation to the
problem of ‘communication’, and is ‘wellsuited’ to this task
– In general, adaptive complexity should be
explained through natural selection
Questions
• Two ways of talking about the evolution of
cognition
– It is interesting in its own right to know how
complex cognitive capacities developed in
evolution
– Knowing the evolutionary trajectory of a particular
ability like language should shed some light on the
question of how the system functions
• The first of these might be a matter of ‘taste’
or interest; the second type says something
more specific, and is more contentious for this
reason
The Critique
• Lewontin’s paper asks in very general terms
how it would be possible to make and test
specific claims about the evolution of
cognition and e.g. language
• His basic argument is that many claims about
evolution of cognition are (1) trivially true, but
(2) we don’t know for sure, and (3) it doesn’t
seem like we find out
Stories
• It’s possible to simply tell plausible stories about
biological properties of organisms.
• In the case of language, there are many such stories;
language is required for communication, hunting,
evolved because of gossip…
This ‘story-telling’ can involve more or less plausible
parts; but ultimately we’re interested in theories that
can be tested, and that’s where most of
Lewontin’s critique is directed.
Principles of Evolution
• Consider the principles that underlie
evolutionary reasoning in general:
– Variation: Variation in physiology/anatomy/behavior among
individuals of a species
– Heredity: Offspring resemble their parents in traits more
than they do unrelated individuals (typically for genetic
reasons)
– Natural Selection: Individuals with certain traits leave more
offspring than individuals with other traits, because
possessing those traits makes them better able to do what
they need to do to survive, reproduce, etc.
Application to
Cognition/Language
• If, then, one is to provide an argument
about how language evolved, several
things have to be done
– It must be shown that there is heritable
variation in cognitive capacities
– It must be shown that individuals with
greater capacities leave more offspring
– Etc.
Problems
• Even when we put aside concerns about
heritability etc., there are problems; a crucial
one is that we are talking about pre-history:
“Our remote ancestors are not preserved in museum collections,
we do not know what kind of heritable variation existed in the
past or exists today…and we cannot measure the survival
advantage, if any, in our remote ancestors of the ability to do
arithmetic.”
Lewontin, p. 111
Specifics
• Some expansions:
– We have no ‘close’ relatives (e.g. 7-10 million years to a
common ancestor with chimpanzees, vs. a few thousand for
dogs and wolves)
– We are not sure who our ancestors are
• Evidence from the fossil record is limited
• Inferences about cognitive abilities have to be based on
e.g. cranial capacity (since stone tools are found in a
number of hominid types)
– How can these limitations add up to what has to
be known for the evolutionary case to be made?
Homology/Analogy
• Another interesting point, which connects with
the last lectures on animal communication :
– Analogous traits: characteristics similar in
function and form between species, but
independent developmentally
– Homologous traits: characteristics connected
with each other by unbroken lines of inheritance
• Tails in mammals: in whales, appendages to
the spine; in seals, modified hind legs. These
are analogous.
For Cognition
• Suppose, then, that we take a
comparative perspective on cognition
• How can we tell the difference between
analogies and homologies?
• How do we define ‘cognition’ in the first
place for comparative investigations,
given that different species are
specialized for different things?
Connections/Conclusions
• Brain areas have homologues between humans and
monkeys/primates, and some functional connections
can be studied (e.g. Broca’s in macaques relates to
facial movements)
• But it isn’t clear what in a primate brain would be
homologous to speech, since primates do not have
speech
• Similar considerations apply in the attempts to teach
language to non-humans; what we see could very
well be analogy, in which case we wouldn’t learn
anything about the evolution of language
• What role should “adaptationism” play (if any)
in the study of language?