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Evolution and Human
Nature
From Sociobiology to
Evolutionary Psychology
13.1 1975 and All That
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In 1975, E. O. Wilson published Sociobiology:
The New Synthesis
ended with an attempt to apply adaptionist
reasoning to human behavior
What are the difficulties of that enterprise?
1. Humans are not very adequate as experimental
animals because:
long-lived
 expensive to keep in captivity
 ethical concerns
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2. Most of our immediate relatives are extinct
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Evolutionary hypotheses about our psychological
and social traits are hard to test by the comparative
method
3. Humans now live in environments that differ
from the environments in which we evolved
food
 artificial light
Tow consequences:
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3.1 Its risky to assume adaptive stability over
significant environmental change
 inference from current utility to evolutionary
cause is very uncertain if the environment has
changed in important ways because a behavior
can evolve for one reason and can be adaptive
now for another
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Zoos and botanic gardens
3.2 Its risky to assume phenotypic stability
 environmental change can change
developmental outcomes
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f. e. European populations are generally much taller
today than 100 years ago, because they eat better
4. What is the appropriate grain of analysis?
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Adaptionist conceptions could over- or
underestimate the extent to which different
properties of an organism form a linked
evolutionary system
5. Adaptation and devolopment: distinct issues
 you can´t use the one to infer the other
 Adaptation does not mean that there is
developmental stability because often input is
needed
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that constitutes facultative traits
Developmental stability does not mean that
there is an adaptation
Insensitivity to environmental factors may be the
result from the developmental system itself or from
adaptive evolution buffering against environmental
disturbance
 Genetic diseases: insensitive to environmental
change, but no adaptation
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13.2 The Wilson Program
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based on the idea that some human behavoirs
are adaptations
populations differ in behavioral profiles that are
heritable
they can be facultative/ conditional or obligate/
unconditional
f. e. incest aviodance, male sexual promiscuity,
femal coyness, infanticide, rape, hostility to
strangers
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evolutionary histories reconstructed from
behavioral traits are similar to those
reconstructed from morphological and genetic
ones
sex role differentiation based on the fact that:
males don´t bear the cost of lactation and
pregnancy and sperm is metabolically cheaper
than eggs
gender differentiation in mating decisions and in
parental care decisions
f. e. males are more promiscuous and females
engage more in parental care
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this pattern of explanation might not work with
humans because,
Human sexual relations have functions additional
to fertilization
femal sexual behavior might be a primate
inheritance rather than a specific human
adaptation > nonselective explanations
human behavioral repertoire is not an aggregation
of independent units
there are connected traits opposed to mosaic traits
behaviors might just be alterable by altering the
underlying mental mechanisms that are used for
many different purposes
13.3 From Darwinian Behaviorism to
Darwinian Psychology
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realization that the psychological mechanisms that
generate behavior are the proper focus of
evolutionary theorizing
biological anthropology as intermediate part of
this transition, represented by Richard Alexander:
Many behaviors are novel and learned on the spot
in response to unusual circumstances
behavior is genuinely diverse and is the
manifestation of a naturally selected learning
rule
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f. e. in the avunculate social system where a man
gives his resources to his sisters´ children rather
than his wife´s children because:
there is lowered confidence in paternity
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happens when society forces wives and husbands to
live seperately
four criticisms of this example and the general
program it represents:
1. grain problem:
 Sociological factors and the general human
motivation to avoid punishment are sufficient to
explain human behavior in the avunculate
societies
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its not necessary to postulate a learning rule to
choose the best reproductive strategy for the
circumstances
2. its hard to measure fitness benefits
 f. e. economic resources don´t correlate with
biological fitness
3. even if fitness benefits are measurable: what are
the possible alternative behaviors?
4. a correlation of behavior and inclusive fitness is
not important when the proximal mechanisms
are missing that produce that behavior
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precise data about the correlation of resource
distribution behavior and inclusive fitness are
not to be expected
when disconfirming data (drug abuse, celibacy)
are mere accidents then the successes could be
mere accidents, too
13.4 Evolutionary Psychology and Its
Promise
there are huge differences among human cultures
 in genetics within group differences are greater than
between group differences and in the cultural realm its
the reverse
 social sciences want to explain the between group
differences with differences in cultural resources
 Evolutionary psychologists (sociobiology´s latest
defenders) are against the division between evolutionary
and cultural theory because
1. human cultural diversity is less intense than it appears
2. diversity itself may have an evolutionary explanation
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f. e. Noam Chomsky´s „language acquisition
device“:
Humanly possible languages are restricted by the
domain-specific cognitive structure
 This device has „switches“ which explain the
differences in language
 ergo: diversity is less than it appears and can be
explained by a single mechanism
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also: inappropriateness of a nature/ culture
dichotomy
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if language is a specific adaptation it must have been
co-evolved with culture
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evolutionary psychologists claim a modular
theory of mind which are Darwinian
algorithms
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module is to be understood in the sense of Jerry
Fodor
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they are: domain-specific, mandatory, opaque and
informationally encapsulated
the task is to find Darwinian algorithms by the
strategy of adaptive thinking:
 infer the adaptation from the ecological context
1. identify the adaptive problems our ancestors
confronted
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2. figure out the correlation between aspects of
the environment they need to know and are able
to know (cues)
3. construct an information-processing design that
could solve the adaptive problem using the
available cues and evaluate possible designs
using the techniques of optimality modeling
4. experimentally test for the existence of the
hypothesized mechanism
13.5 Evolutionary Psychology and Its
Problems
there are two problems of the standard formulation of
evolutionary psychology
1. there is no invariant environment to which the lineage
can be adapted to
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the social environment and the lineage change together
2. modules are vulnerable to exploitation in a malign
world
 language: a rigid module couldn´t evolve because it
wouldn´t be exploited since individuals want to
understand each other in the first place
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an arms race in the evolution of language would require a
non-modulare language acquisition device
our cognitive skills are too complicated, and
there is too little input from the environment,
for their development to be the result of a
general learning mechanism
 poverty of the stimulus argument
 3 objections to this point:
1. even superior performance in a certain cognitive
area is not sufficient to claim a Darwinian
algorithm
 f. e. chess and car driving are domain-specific
and widely spread through the population but
they cannot be based on a Darwinian algorithm
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2. the poverty of the stimulus argument does not
support some of the central hypotheses of
evolutionary psychology
 f. e. Cosmides and Tooby claim that we have a
module of social exchange
 their reasoning is the inverse of poverty of the
stimulus reasoning
 f. e. Wason card selection task is computationally
easy but we need the right input
3. many important problems cannot be solved by
a modular mechanism
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f. e. the pragmatics of language cannot be
handled by a specialist device because everything
the hearer knows is important to decode the
speakers intent
these two problems are linked because:
the adaptive problem is always being
transformed in an arms race and hardwired
mechanisms are vulnerable to deception in such
a fierce world
Cognitive adaptation often transforms the
environment rather than being an accomodation
to it
so the methodology of discovering the
mechanisms by first trying to discover the
problems is not adequate
 it overlooks the interactive character of social
evolution
 the problem culminates if population structure
plays a role in human evolution because
1. population structure is clearly not a stable
background against which psychology changes
2. there are different adaptions to expect
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f. e. many altruistic behaviors could evolve in a
structured population what would otherwise not be
the case
13.6 Memes and Cultural Evolution
cultural life itself can be seen as an autonomous
evolutionary process
 in Dawkins´s language, ideas are memes that
ought to show phenotypic variation, differential
fitness, and heritability
 3 reasons against this concept:
1. there may be no thing as cumulative selection in
the cultural realm
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2. there is no active designer in natural selection
but there is one in cultural evolution
 an exception could be the domain of science
with the growth of objective knowledge over
time
3. in the explanatory idea „survival of the fittest“
fittest means expected reproductive success, but
there is no explanation of the nature of the
fitness of ideas (with the possible exception of
scientific ideas)