Download Evolutionary Psychology

3/30/2012
Evolutionary
Psychology
Human
Behavioral Ecology
Focus on
Universals
Variation/Diversity
Assumed
Selective
Environment
Environment of
Evolutionary
Adaptedness
Present
Environment
How measure
Adaptation?
Design Criteria
(re EEA)
Reproductive Success
or ‘Fitness’
Usual study
population
Modern societies
Traditional societies
Two Contrasting but Complementary Evolutionary
Perspectives on Human Behavior:
Evolutionary Psychology (EP) – derived from a
synthesis of biology and psychology
Human Behavioral Ecology (HEB) – derived from a
synthesis of biology and anthropology
I think these are legitimate and complementary
perspectives. So do Barrett, Dunbar & Lycett (text).
Environment of Evolutionary Adaptedness (EEA)
Environment of Evolutionary Adaptedness (EEA)
Hunter-gatherer (foraging) society: Subsistence gained from
hunting animals,fishing, and gathering edible plants in the wild,
without domestication of animals or of plants (agriculture).
Relatively small, simple band level of social organization.
Hunting and gathering is thought to have been the only
subsistence strategy employed by hominid societies for more
than two million years, until about 10-15,000 years ago.
“The environment that humans – and, therefore, human minds
– evolved in was very different from our modern environment.
Our ancestors spent well over 99% of our species' evolutionary
history living in … small, nomadic bands of a few dozen
individuals who got all of their food each day by gathering
plants or by hunting animals. Each of our ancestors was, in
effect, on a camping trip that lasted an entire lifetime, and this
way of life endured for most of the last 10 million years.”
Cosmides & Toobey: Evolutionary Psychology: A Primer
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Environment of Evolutionary Adaptedness (EEA)
Environment of Evolutionary Adaptedness (EEA)
““Our species lived as hunter-gatherers 1000 times longer than
as anything else. [Our familiar] world … with roads, schools,
grocery stores, factories, farms, and nation-states, has lasted
for only an eyeblink of time when compared to our entire
evolutionary history… Agriculture first appeared on earth only
10,000 years ago, and it wasn't until about 5,000 years ago
that as many as half of the human population engaged in
farming rather than hunting and gathering.”
“Natural selection is a slow process, and there just haven't
been enough generations for it to design circuits that are welladapted to our post-industrial life … In other words, our
modern skulls house a stone age mind. The key to
understanding how the modern mind works is to realize that its
circuits were not designed to solve the day-to-day problems of
a modern American -- they were designed to solve the day-today problems of our hunter-gatherer ancestors…”
Cosmides & Toobey: Evolutionary Psychology: A Primer
Environment of Evolutionary Adaptedness (EEA)
“Evolutionary psychology is relentlessly past-oriented.
Cognitive mechanisms that exist because they solved
problems efficiently in the past will not necessarily generate
adaptive behavior in the present. Indeed, EPs reject the notion
that one has "explained" a behavior pattern by showing that it
promotes fitness under modern conditions … Although the
hominid line is thought to have evolved on the African
savannahs, the environment of evolutionary adaptedness, or
EEA, is not a place or time. It is the statistical composite of
selection pressures that caused the design of an adaptation.”
Cosmides & Toobey: Evolutionary Psychology: A Primer
Key point about EEA: mismatches between modern
environments and the EEA will inevitably compromise
the effectiveness of human adaptations that evolved
in the EEA. This compromised effectiveness is called
adaptive lag.
Natural Selection or Cultural Selection?
The two can work hand in hand: co-evolution or
biocultural evolution.
Cosmides & Toobey: Evolutionary Psychology: A Primer
Environment of Evolutionary Adaptedness (EEA)
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Tenets of Evolutionary Psychology
5. The Mind as a set of specialized modules
1. Psychological mechanisms – not behaviors – have been
shaped by natural selection to enhance reproductive
success.
2. Mechanisms have many effects (‘side effects’) besides the
favorable (selected) effects. And these side effects can be
maladaptive.
3. The historical ecological context (EEA) in which human
evolution occurred is different from the contemporary
context, especially those of “modern” societies.
4. Therefore, a given trait may be:
(a) adaptive;
(b) a maladaptive side effect of an otherwise adaptive
mechanism; or
(c) a maladaptive interaction of an out-of-date adaptive
mechanism with a new environmental context.
Evolutionary Psychology vs. Human Behavioral Ecology
EP
HBE
Evolutionary
Psychology
Human
Behavioral Ecology
Focus on
Universals
Variation/Diversity
Assumed
Selective
Environment
Environment of
Evolutionary
Adaptedness
Present
Environment
How measure
Adaptation?
Design Criteria
(re EEA)
Reproductive Success
or ‘Fitness’
Usual study
population
Modern societies
Traditional societies
Daly & Wilson 1999 vs. Smith, Borgerhoff Mulder & Hill 2000
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Daly & Wilson 1999
“Interpretative pitfalls await those who disregard the possibility
of mismatch between contemporary environments and the
EEA. “
Example: Kalick et al (1998): no correlation between
attractiveness at 17-18 and prior or future health status –
therefore a ‘Fisher runaway’ effect, not a ‘good genes’ effect.
Blinded by beauty.
Daly & Wilson 1999
True evolutionary approach “carves the psyche more nearly at
its joints”.
“Freud … never grasped the fundamental Darwinian insight
that the ultimate criterion of adaptive functional organization is
its contribution to fitness”.
Symons (1989): “measuring reproductive attainment
[contemporaneous reproductive fitness] is not the test of a
Darwinian approach”.
But “the ancestral information value of attractiveness cues
[i.e., predictive of good health in the EEA] might have been
obscured by modern medicine, good nutrition, or other
aspects of life in 20th-century, urban California”.
EPs accuse HBEs “of treating inclusive fitness as a motive or
objective rather than as the historical arbiter of the selective
retention of attributes, and thus of imagining that evolution
imparts a magic ability to find the course of action that
maximizes inclusive fitness even in the face of evolutionarily
unforeseen challenges.”
Smith, Borgerhoff Mulder & Hill 2000
Smith, Borgerhoff Mulder & Hill 2000
Contrast Evolutionary Psychology (EP) and Human
Behavioral Ecology (HBE).
1. Use of formal models and deductive theory (9HBE)
To considerable extent EP and HBE are complementary,
differing in relative emphasis placed on psychological
mechanism versus manifest behavior
But they diverge in other, controversial ways:
1. Use of formal models and deductive theory (9HBE)
2. Emphasis on domain-specific cognitive algorithms (9EP)
3. Relationship between psychological mechanisms and
observed behavior (9EP)
4. Assertions regarding adaptive lag and adaption to past
environments (EP↑ HBE↓)
5. Views on the relevance of fitness measures to analyses of
contemporary behavior. (EP↓ HBE↑)
2. Emphasis on domain-specific cognitive algorithms (9EP)
“… fitness maximization is often a better predictor of
behavioral patterns than is pursuit of any one specific goal
… presumably because nature is full of trade-offs, and
organisms have evolved mechanisms to appropriately
weigh different goals and currencies. While partitioning
adaptive problems into discrete real-world problem
domains (such as mate assessment, kin recognition,
parental investment allocation, and threat and bluff) may
‘carve the psyche more nearly at its joints’, it is not at all
clear how EP helps us analyze the myriad situations where
these domains interact in determining adaptive payoffs”.
Need optimization and ESS models.
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Smith, Borgerhoff Mulder & Hill 2000
3. Relationship between psychological mechanisms and
observed behavior.
“The central problem here is that behaviour is unlikely to be a
simple expression of evolved psychological mechanisms, but
rather a complex outcome of interaction between such
mechanisms and psychological, social and cultural
dynamics”.
“In practice…the EP research strategy often ends up simply
ascribing behavioural patterns, or verbal statements about
preferences, to hypothesized psychological mechanisms”.
Mate choice as example: EP studies has revealed lots about
“the sexual and parental cues men look for in women, and
vice-versa … [but little about] how they are used in the real
world of mating markets and biological clocks”.
Smith, Borgerhoff Mulder & Hill 2000
5. Views on the relevance of fitness measures to analyses of
contemporary behavior. (EP↓ HBE↑)
Smith, Borgerhoff Mulder & Hill 2000
4. Assertions regarding adaptive lag and adaption to past
environments (EP↑ HBE↓)
“In practice, the evolutionary part of EP often reduces to rather
vague claims about selective conditions in the EEA that may
have favoured the evolution of a hypothesized psychological
mechanism … To the extent that our knowledge of the EEA
remains sketchy, rigorous quantitative testing of precise
selectionist hypotheses becomes virtually impossible, and the
result can easily degenerate into adaptive storytelling”.
“In contrast, HBE researchers begin with the assumption that
evolved conditional strategies, learning biases, and social
information transfer will produce adaptive outcomes, most of the
time, even in relatively novel environments.
“…pointing to the negative side of a given trade-off…does not
provide valid grounds for concluding that the trait is maladaptive”
trout example
Cultural selection and natural selection can work
to the same end
Genes
EP researchers: fitness measures are irrelevant to
evolutionary analyses of current behaviour.
“…in our experience the fitness-maximization assumption
usually comes closer to predicting observed behaviour than
an assumption that fitness consequences are irrelevant.”
Memes
Natural
selection
trait
Cultural
selection
trait
“…EP researchers are all too ready to assume that a given
trait maximized fitness in the EEA (a truly untestable
assertion) even as they find fitness measures irrelevant in
the present”.
fitness
fitness
Meme: a unit of
cultural ideas,
symbols or
practices, which
can be
transmitted from
one mind to
another through
communication.
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