EVOLUTIONARY DETERMINANTS OF HUMAN INTELLIGENCE

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EVOLUTIONARY DETERMINANTS OF HUMAN INTELLIGENCE
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PRESENTATIONS

• GREEN RED
• 1. ECOLOGICAL
• AND SOCIAL THEORY 225 581
• 2. SEXUAL SELECTION,
• CO-EVOLUTION 227 583
• 3. BRAIN SIZE AND
• INTELLIGENCE 228 584

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ARGUMENT

• Intelligence must have been selected over
  generations because it is likely that more
  intelligent individuals had a better chance of
  survival than less intelligent ones.

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ECOLOGICAL THEORY225, 581

• Ecological environmental
• Foraging searching for food.
• A good memory would help in the search for
  seasonal foods in particular.
• Hunting requires cognitive abilities. Can you
  suggest any?
• Planning
• Coordinating with others (language)
• Problem solving
• Ecological theory proposes that it was foraging
  demands which led to the reproductive success of
  those with good mental abilities.

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TOOLS

• Use of tools is associated with foraging. Flints
  were used for cutting, gathering and eating.
• Stone tools were used 2.5 million years ago.
• Those who used tools would have an evolutionary
  advantage over those who didnt.

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SOCIAL THEORY225, 581

• Another view is that intelligence evolved as a
  result of problems of group living.
• Groups confer many advantages on individuals.
• Can you think of any?
• Predators - can have lookouts
• Mating is facilitated
• Cooperative hunting

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GROUP LIFE

• An individual who can solve social problems is
  more likely to survive and reproduce.
• He/she will be better at cooperating and will be
  more aware of other relationships.
• These abilities are likely to have been subject
  to selective pressure.

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THEORY OF MIND

• We understand other peoples thoughts and
  emotions and recognise that they are different
  from ours.
• Some people, e.g. autistics, do not possess this
  ability. They find relationships more difficult.
  Without a theory of mind, these people are
  likely to be socially withdrawn.

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MACHIAVELLIAN INTELLIGENCE

• This is the ability to detect cheats, and is
  related to the theory of mind. A cheat needs to
  understand another persons view of the world.
  Being able to detect cheats is adaptive, because
  cheats undermine social behaviour.
• COSMIDES 89 demonstrated that humans are very
  good at solving puzzles related to social
  concerns, especially if there is the possibility
  of cheating.

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EVALUATION OF SOCIAL THEORY

• intelligent animals are highly social
• almost all primates are social. So are
  dolphins, whales, elephants and lions.
• - cannot know which came first, sociability or
  intelligence

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ECOLOGICAL VS SOCIAL THEORY 226, 582

• DUNBAR argued that neocortex (newest bit of
  brain) is most responsible for higher order
  thinking. Animals living in groups have a larger
  neocortex.
• There is no correlation between environmental
  complexity and size of neocortex.
• So which theory does this support?

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SEXUAL SELECTION THEORY 226, 582

• Maybe intelligence was sexually selected, i.e.
  seen as a sexy trait.
• What sexy behaviours might intelligence be
  connected to?
• Ability to be entertaining
• Successful at hunting
• Ability to solve problems
• If it works in the same way as a peacocks tail,
  then females would select intelligent men and
  this would strengthen the intelligence trait in a
  population.

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RUNAWAY HYPOTHESIS

• Men may have been more creative in the arts
  because it was a sexy trait to be creative.
• Women would have needed to be intelligent to
  decode mens abilities

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IS INTELLIGENCE SEXY?

• Miller 96 in surveys investigating what people
  look for in partners, intelligence consistently
  comes at top of list, even though it is not
  directly related to reproductive success.
• Name some which ARE directly related to
  reproductive success.

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EVALUATION

• Health, fertility and command of resources are
  directly related to reproductive success. So
  intelligence is thought to be a runaway trait.
• BUT
• Relationships are based on many factors, not just
  intelligence.
• The argument FOR intelligence being sexually
  selected is the rapid change in the size of brain
  in humans
• In the last 3 million years brain size has
  trebled.
• Sexual selection leads directly to reproductive
  success, so it could explain the rapidity of
  change.

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CO-EVOLUTION

• Mental abilities and brain growth possibly
  co-evolved.
• Predator runs fast ? prey runs even faster.
• If prey die out, so does the predator, so they
  had to co-evolve.
• Dawkins proposed that good mental abilities were
  advantageous for survival and reproduction. So
  brain growth needed to occur to accommodate these
  abilities.

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THE HUMAN BRAIN P.583

• CROW proposed that an abrupt change in the
  wiring of the brain occurred which increased
  language and helped us gain control of the earth.
• Read blue box p. 227, 583.
• 100,000 years ago, Neanderthals existed in
  Europe.
• Homo Erectus in Far East.
• Then Homo Sapiens emerged out of Africa and
  spread very quickly.

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GIFT OF THE GAB

• 30,000 years ago, only Homo Sapiens was left. So
  must have had a key advantage over the other
  species.
• Most scientists agree this was probably language.
  CROW proposed a freak mutation occurred in a
  male gene (on the Y chromosome) of one man.
• The first man to manifest the gift of the gab
  probably had many sexual mates and his genes
  would have spread quickly.
• BUT
• Our sophisticated language occasionally goes
  wrong and triggers Schizophrenia, which is
  accompanied by linguistic breakdown.

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BRAIN SIZE AND INTELLIGENCE P.228, 584

• Human brain is significantly larger
  (proportionately) than any other animal brain.
• BUT
• Bigger brains incur a physiological cost, and
  make birth more difficult. So there must have
  been an adaptive advantage or it would not have
  been naturally selected.

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EVIDENCE

• RUMBAUGH 96 found that animals with larger
  brains are capable of more intelligent behaviour.
  
• 12 different primates were trained to perform a
  task e.g. pick up a square rather than a triangle
  to find food. Then they were trained on a 2nd
  task, e.g. pick up a circle rather than a
  hexagon.
• Findings what were they? (228, 584)

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FINDINGS

• Larger brained primates (gorilla, chimp)showed
  transfer of learning (intelligent behaviour) more
  than smaller brained primates (lemur, talapoin).
• Smaller brained animals showed more interference.
• BUT
• Animals were being tested in an unnatural setting
  doing an unnatural task.
• Kalat 98 found that rats were unable to pick an
  odd one out on a visual task, but could on an
  olfactory one. (3 items/3smells)

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CORRELATING IQ AND BRAIN SIZE P. 229, 585

• Skull size is not a good indicator of brain size.
• MRI provides accurate measurement.
• WILLERMAN 91 used MRI to correlate IQ and brain
  body ratio. He found a correlation of 0.51 in
  college students between brain size and IQ.

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BRAIN SIZE AND BIRTH

• Human brains are bigger than any other primate.
  Brain size is obviously caused by genes, but
  comparing humans may have more to do with
  environment. Why?
• Brain development is linked to improved diet,
  especially during pregnancy. Most brain growth
  occurs before birth.
• LUCAS 92 breast fed babies have higher IQs
  later in life. Breast milk contains fatty
  substances important in brain growth.

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IQ AND SEX

• Men have bigger brains than women but also larger
  bodies.
• It is not size as much as brain organisation
  which matters.
• Women have a larger corpus callosum. This is the
  nerve fibres which connects the hemispheres to
  each other. This could explain why they
  communicate better.

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EINSTEINS BRAIN

• This was examined after his death. It was normal
  in size and structure, but differences in
  organisation could be seen
• What were they? (229, 585)
• Neurons in prefrontal cortex were more highly
  packed.
• But cause or effect cannot be established.
  However it does show that it is brain
  organisation, not size, which matters. The human
  brain is particularly well organised, because
  different functions are localised, i.e. different
  parts of the brain have different functions.