Why Baboons Dont Have History

1
Why Baboons Dont Have History

• Culture and human adaptation
• Culture and design
• Culture and ultimate causation

• Culture and design
• Culture and ultimate causation

2
Modal Social Science Human behavior is highly
flexible, not innate

• Innate, genetically transmitted behaviors are
  rigid inflexible
• Human behavior is flexible, determined by
  environments not genes

3
Evolutionary Psychology Flexibility requires
more instincts, not fewer

• Phenotypic flexibility requires innate
  information
• Environmental cues predict best behavior
• Mapping depends on innate information
• More information allows
• more accurate adaptation, or
• adaptation to a wider range of environments
• Limited information storage ? tradeoff between
  accuracy and generality
• Mechanisms which allow highly accurate learned
  adaptation work in limited environments, e.g.
  indigo bunting navigation
• Crude mechanisms based on statistical association
  or trial and error work in wider range of
  environments

4
Thought experiment

• Chacma baboons live in a variety of habitats.

• Suppose we transplanted groups of baboons between
  habitats.
• Allow no contact with other baboons new area.
• Prediction Rapid convergence to local behavior
  and social organization.

5
A second thought experiment

• Humans live in a variety of habitats.

• Suppose we transplanted groups of humans between
  habitats.
• Allow no contact with other humans new area.
• Prediction Some convergence to local behavior
  and social organization, but many persistent
  differences.

6
Culturally evolved adaptations allowed foragers
to occupy a wider ecological range than any other
species
7
Social learning allows unspecialized learning
mechanisms to give rise to complex adaptations in
many small steps

• Imitation finesses the accuracy-generality
  trade-off
• Key design information stored in brains not genes
• Unspecialized mechanisms allow small improvements
  to existing solutions
• Repeated application over generations creates and
  maintains accurate adaptations

8
Why Baboons Dont Have History

• Culture and human adaptation
• Culture and design
• Culture and ultimate causation

9
Culture is part of the design problem for human
psychology

• Adaptationist reasoning requires specification of
  design problem
• Evolutionary Psychology ignores culture when
  specifying design problem for human psychology
• Cognition evolved to solve problems for a small
  group living foraging species
• Culture is the result, not cause of psychology
• Humans were just smarter chimpanzees

10
E.g. Imitation not important
But why would selection ever produce a
psychological mechanism That specifies a rule
such as detect the features of female bodies
that those around you perceive as attractive and
perceive those as attractive yourself?...If there
were such a mechanism, standards of sexual
sexual attractiveness would be as arbitrary as
the relationship between the word apple and the
fruit. There would be no consistent
relationship between standards of attractiveness
and female mate value. An evolutionary
psychologist
11
Wrong because social learning creates feedback
between psychology and environment
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A model in which imitation reduces learning costs

• Large population of organisms
• Environment has two states 1 2
• Switches states with constant probability each
  time period
• Two behaviors
• Behavior 1 favored in environment 1
• Behavior 2 favored in environment 2
• Two genotypes
• Learners observe environmental cue and choose
  behavior
• Imitators copy a random individual

13
Learning leads to errors when cues are imperfect
predictors of environment
Trait 1 Favored
Trait 2 Favored
Environmental Cue
14
Imitation evolves
but doesnt change average fitness
0
1
Frequency of Imitators
15
Can add complications without changing result

• Multiple traits, multiple environments
• Spatial variation
• Imitators can identify learners

Reason

• Learners allow population to track environment
• Spread of imitators reduces quality of
  information available to imitators.
• Spread continues until both types have the same
  fitness

16
Imitation increases average fitness when it makes
individual learning more efficient
0
1
Frequency of Imitators
17
Two ways imitation can make individual learning
more efficient

• Social learning allows cumulative cultural
  adaptation
• Small improvements less costly per unit than big
  ones
• Copy learn less costly than learning alone
• Social learning allows selective learning
• Cost or accuracy of learning situations vary
• Learn when learning is cheap or accurate
  otherwise copy is less costly than learning alone

18
Imitation allows selective learning
Trait 1 Favored
Trait 2 Favored
Environmental Cue
19
Imitation allows selective learning ? increase
average fitness
Learners
Average Fitness
Imitators
Frequency of Imitators
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If learning is error prone and environments
change slowly, the ESS amount of imitation can be
substantial
1.0
g 0.02
g 0.05
Slower Environmental Change
Equilibrium Probability of Imitation
g .25
0.0
0.0
2.0
Standard Deviation of Environmental Cue
More Error Prone Learning
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What is the best way to use social information?

• So far how to balance social and non-social
  information
• Environment provides cues
• Behavior of others provides cues
• When should individuals depend on one or the
  other?
• But, the distribution of behavior among models
  also provides cues
• Commoness Is everybody doing it? Or, just a few?
• Prestige Are cool people doing it? Or,
  everybody?
• Similarity Are people like you doing it? Or,
  other kinds of people?
• Can use population methods to investigate how
  selection should shape the psychology responds to
  social cues

22
Selection favors imitation of the prestigious

• Imitate the successful provides good short-cut
  for hard to evaluate traits
• Some traits lead to success
• Dont know which ones
• Imitate all traits plausibly connected to success
• People will pay to get close to successful
• Deference
• Resources
• Amount of deference a good index of success
• May explain prestige psychology in humans

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Model makes many testable predictions

• People will copy prestigious individuals, even
  outside their range of expertise

• Skilled individuals have higher prestige
• Older individuals will have higher prestige
• Skilled or knowledgeable individuals will get
  goodies
• Prestigious people are memorable
• Prestige is associated with a different ethology
  than dominance

24
Why Baboons Dont Have History

• Culture and human adaptation
• Culture and design
• Culture and ultimate causation

25
Culture allows the spread of maladaptive behavior

• Benefit evolve fancy, habitat specific
  adaptations using unspecialized psychological
  mechanism
• Cost have to be credulous
• Result Maladaptive ideas can spread
• Many examples
• Dangerous hobbies
• Drug use
• Academic careers
• But, why should they spread?

26
Natural selection leads to the spread of
maladaptive cultural variants

• People in influential social roles play may be
  important in cultural transmission
• Teachers, Bosses, Rock-stars in contemporary
  society
• Warriors, political leaders, religious
  specialists in smaller scale societies
• People vary in their success in attaining
  influential social roles
• This variation is affected by beliefs and values
• Cultural variants that lead to success in
  attaining influential social roles will tend to
  spread
• Such variants may often be maladaptive
• Famous climbers take horrendous risk
• Successful academics give up family success

27
Both birth and death rates have fallen as
countries industrialized

• Growth in wealth associated with modernization
  leads to a demographic transition

• Before industrialization European population
  growth was low
• High birth rate, but
• Also high death rate
• As industrialization begins death rates fall
• Followed by a fall in birth rates
• Leading to low population growth

28
Economic development leads to new patterns of
cultural transmission

• Pre-modern agrarian societies
• Most people live in isolated villages with little
  exposure to elites
• Elite prestige is inherited not earned
• Local prestige associated with large families
  (especially true for women)
• Modernizing societies
• Literacy and urbanization lead to extensive
  social contact
• Modernizing economy provides much wider
  opportunities for increased wealth/prestige
• But, positions require education, delayed
  marriage
• Competition for status leads to spread of
  preferences for goods that signal status

29
Anabaptist groups have not undergone transition
despite great prosperity

• Hutterites

• Live mainly in Saskatchewan
• Large, modern mechanized farms

• Amish

• Mainly in Pennsylvania
• Family farms with little mechanization
• Both groups
• Very successful economically
• Minimize public schooling
• Minimize contact with non-Anabaptist
• Very high birth rates

30
Rapid cumulative adaptation ? novel evolutionary
processes

• Adaptation stronger compared to diffusion in
  cultural evolution than genetic evolution
• Many equilibria are likely for many reasons
• Ordinary adaptive problems have many solutions
• Network externalities
• Conventions
• Repeated social interactions
• Conformist social learning

• Strong adaptation multiple equilibria between
  group variation

• Stable variation between groups ? novel
  evolutionary processes

31
The 19th century expansion of the Nuer is an
example of cultural group selection.
1800
1840
1880
Nuer
Dinka
Drawn from data in Kelly 1985
32
Nuer expansion resulted from cultural differences
between Nuer and Dinka.

• Nuer and Dinka exploited same habitat using same
  technology.
• Each group consisted of a 10 to 30 independent
  polities.
• Striking cultural differences between two groups

Data from Kelly 1985
33
Natural selection acting on culture is an
ultimate cause

• Why do birds fly south in the winter?
• Proximate day length cues lead to hormonal
  changes, etc.
• Ultimate Birds who did this in the past had more
  offspring
• Why do people in modernizing societies have so
  few children?
• Proximate because they have acquire ideas/values
  that cause them to allocate resources to other
  activities
• Ultimate Because people with such ideas were
  more influential in cultural transmission
• Depends on genesso what?
• Same traits may be influenced by other ultimate
  causes.

34
This jasper scarab with an engraved baboon was
recovered from the Late Bronze Age ship wreck
site of Uluburun near the southern coast of
Turkey.