Introduction to Evolutionary Psychology Psychobiology NOH Hope Park 2005

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Introduction to Evolutionary PsychologyPsychobiol
ogy NOH Hope Park 2005
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Evolutionary Psychology
EVOLUTIONARY PSYCHOLOGY Evolutionary basis of
behaviour and culture Humans are animals and have
been subjected to the same processes of
evolutionary change as all other living things on
earth (e.g. John Tooby, Leda Cosmides, David
Buss, Martin Daly, Margo Wilson, Donald Symons,
Laura Betzig, Steven Pinker
SOCIOBIOLOGY Evolutionary explanations of social
behaviour (e.g. Wilson, 1975)
Criticises the SSSM (Standard Social Science
Model) as being cut off from the natural
sciences We are products of biology and culture,
nature and nurture
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Charles Darwin (1959) The evolution of species
through natural selection
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Darwins finches
Famous for their beaks
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Galapagos IslandsHome to Darwins finches

• A single species of finch landed on one of the
  islands thousands of years ago
• Due to overcrowding and food shortages the
  finches spread to the other islands
• Because the food on different islands was
  different, a variety of beaks was usefull

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Darwins finches
Beaks specialized tools for specific tasks
How was this diversity of beaks formed by natural
selection?
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Variation

• All individuals within a species show variation
  in their behaviour, morphology or physiology
• This variation is called the PHENOTYPE
• The basis for this variation lies in the genes of
  the individual. The genetic variation is called
  the GENOTYPE
• Genotype Environment Phenotype

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Inheritance

• Genetic traits are inherited from parents, and
  are passed on to offspring
• Offspring resemble their parents more than other
  individuals in the population
• Evolution is about passing on your genes to the
  next generation Fitness is measured in terms of
  surviving and reproducing offspring

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Adaptation

• Individuals compete for food, mates and shelter
• Some traits help organisms to compete, survive
  and reproduce
• Thus, favourable traits are selected and passed
  on to the next generation.
• The favourable traits are called ADAPTATIONS

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Biological adaptations

• An anatomical structure, a physiological
  process, or a behaviour pattern (psychological
  mechanism) that made an ancestral organism more
  fit to survive and reproduce in competition with
  other members of its species
• Psychological adaptations difficult to study- no
  direct fossil evidence!

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Consequence natural selection

• Some individuals are better competitors and leave
  more offspring
• The offspring will have inherited their parents
  successful traits
• Trough this process organisms become adapted to
  their environment natural selection can be said
  to have taken place
• The success of a trait relative to other traits
  is called its fitness a measure of relative
  reproductive success

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Example Bipedal locomotion in humans
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Example Bipedal locomotion in humans

• Variation early hominids showed variation in
  their posture
• Inheritance This variation was under genetic
  control, and was passed from parents to offspring
• Selection Individuals with more upright posture
  survived longer and produced more offspring
• Adaptation Thus, upright posture made us better
  adapted to our environment (physical and social)

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Speciation

• Phenotypic traits environment genetic makeup
  (or genotype)
• Natural selection will favour individuals with
  certain genotypes
• Reproductive isolation will then result in
  speciation Beaks of Darwins finches

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Tinbergens 4 WhysExample Human Language

• Mechanistic (or proximate cause)
• Developmental (or ontogenetic)
• Historical (or phylogenetic)
• Functional (or ultimate)

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Study of human behaviour

• Human behavioural ecology (HBE) focuses on
  behavioural traits that promote differences in
  fitness between individuals (i.e. leave more
  offspring)
• Evolutionary psychology focuses on what has
  shaped the human psyche over evolutionary time
  and whether our psychological mechanisms are
  designed to solve adaptive problems (e.g.
  detecting cheats)

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Environment of Evolutionary Adaptiveness (EEA)

• Humans have been hunter-gatherers for most of our
  existence
• Part of our psychological make up has evolved in
  the ancestral conditions (the EEA)
• Stone age minds in modern world??? Perhaps some
  of our behaviour is not adapted to modern day
  living.

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Criticism for EEA

• When and where exactly was the EEA? Surely our
  ancestors were faced with multitudes of social
  and physical conditions
• Some aspects of human adaptations are recent
  (e.g. the enzyme that breaks up lactose), perhaps
  some psychological adaptations are recent as
  well?
• Human behaviour is flexible- we show phenotypic
  plasticity! Learning plays a big part.

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Evolutionary Psychology

• 1. Problems humans encountered in the ancestral
  environment
• a) Finding a vigorous healthy mate
• b) Forming reciprocal co-operative relationships
• c) Avoiding brother-sister mating
• 2. Psychological tools that evolved to help solve
  those problems
• d) Vigourous dance/sports indicating health
  strength
• e) Detecting cheaters in these relationships
• f) Adult sexual aversion to childhood intimates
• 3. The way those tools function now
• g) Vigorous movements in dance sport
• h) Gossip that helps us learn about cheaters
• i) Shim pau marriages, kibbutzim sexual
  attraction, attraction between brothers sisters
  reared apart

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Evolved Psychological Mechanism

• ? A set of genetically coded decision processes
  that enabled ancestral organisms to carry out
  cost benefit analyses in response to a specific
  set of environmental contingencies, and
• ? that organized the effector processes for
  dealing with those in such a way that the gene(s)
  producing the decision processes were reproduced
  better than alternate gene(s).
• ? The costs and benefits are ancestral
• ? The mind is an organized integration of
  evolved psychological mechanisms

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The modular mind
Cheat detection
Mate choice
Face Recognition
Tool Use
Theory of Mind
Language
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Genes as units of selection

• Natural selection is about individual survival,
  and not survival of the species
• Selection acts on the whole organism, but what
  changes over time are a genes frequencies in the
  population gene pool
• The gene is the unit of selection giving rise to
• adaptations "The Selfish Gene.
• Replicators (genes) versus Vehicles
  (organisms)

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The problem of altruism

• Altruistic act an act that has a cost to the
  actor but increases the fitness of the recipient
• Reduces personal fitness
• Increases the fitness of competitors
• Shouldnt it be selected against?

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Some Real Cases of Altruism inthe Animal Kingdom

• Helpers at the nest
• Grooming
• Food sharing.

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How to Solve the Puzzle of Altruism

• See how selfish (nonaltruistic) genes can
• give rise to unselfish (altruistic) individuals.
• An important distinction! Metaphorical
• selfishness of the genes does not imply real
  selfishness of people.

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The problem of altruism

• Problem
• The selfish individuals
• contribute more to the
• next generation
• UNLESS
• Some other selection
• pressure selects for
• altruism

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Kin selection and Hamiltons Rule

• A gene can benefit copies of itself that reside
  in other individual
• bodies, i.e. close relatives carry some of our
  own genes (hence kin selection)
• Inclusive fitness direct fitness indirect
  fitness

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Hamiltons rule c lt rb

• c cost of altruistic act
• b benefit to recipient
• r coefficient of relatedness
• Coefficient of relatedness proportion of genes
  that are identical by descent from recent
  common ancestor

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Examples of r

• You to yourself 1.0
• Parent/child .5
• Full sibling .5
• Half sibling .25
• Grandparent/Grandchild .25
• Uncle/Aunt/Niece/Nephew .25
• First Cousin .125
• Identical twins 1.0
• Id give my life for 2 brothers or 8 cousins. -
  J.B.S. Haldane

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• On the basis of Hamiltons theory, evolutionary
  psychologists generated two hypotheses regarding
  altruism
• Hypothesis A Helping behaviour increases as the
  degree of genetic overlap increases between the
  helper and the recipient.
• Hypothesis B Helping behaviour increases as the
  reproductive potential of ones kin member (i.e.
  relative) increases.

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Imagine this situation . . .

• Your 7-year old cousin, your 75-year-old
  grandmother, and a 21-year-old acquaintance are
  all asleep in different rooms of a rapidly
  burning house, and you have time to rescue only
  one.
• Who are you most likely to help? Who are you
  least likely to help?
• from Burnstein et al. (1994) JPSP 67 773-789