Module 5 Genetics_ Evolutionary Psychology and Behavior

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Module 5 Genetics_ Evolutionary Psychology and Behavior Powered By Docstoc
					          Module 5

Genetics, Evolutionary Psychology
           and Behavior
Topics we were born to learn about

 Behavior Genetics and Individual Differences
 § Genes: Molecules that code for life
 § Learning about heredity from Twin and
   Adoption Studies
 § Gene-Environment Interaction
 Evolutionary Psychology: Adaptive Success
 § Artificial and Natural Selection
 § Critiques of Evolutionary Thinking
Behavior Genetics:
Predicting Individual Differences

More ways of exploring the           Behavior geneticists
origins of the biology of            study how heredity
                                      and environment
behavior:                               contribute to
•Understanding genes                 human differences.
•Twin and adoption
                                    Let’s start by looking
•Gene/environment                   at GENES.
•Evolutionary Psychology
The Building Blocks of
Heredity and
 Genes are
 parts of DNA
 which are
 found in
 in the nuclei of

                         (Deoxyribonucleic Acid)
Chromosomes are made of DNA,
   which are made of genes.
   Chromosome:                 DNA:
threadlike structure   a spiraling, complex
made largely of DNA    molecule containing
     molecules                 genes

Chromosomes and Inheritance
§ The human genome includes 46
  chromosomes in 23 sets
  matched sets; each
  chromosome has the same
  gene locations.
§ This includes the X and Y
  chromosomes, not a matched
  set in males, who are missing
  some genes on the Y.
§ A biological parent donates half
  his/her set of chromosomes to
  his/her offspring.
§ We received half a set of
  chromosomes from each
  biological parent.
The Human Genome:                      The genome: an
                                       organism’s entire
20,000 to 25,000 Genes                collection of genes
§ Human genomes are so nearly
  identical that we can speak of
  one universal human genome.
§ Yet tiny genetic differences
  make a difference. If there is a:
   § .001 percent difference in
     genome, your DNA would
     not match the crime
     scene/you are not the
     baby’s father.
   § 0.5 to 4 percent difference
     in genome, you may be a
   § 50 percent difference in
     genome, you may be a
         How Genes Work
§ Genes are not blueprints;
  they are molecules.
§ These molecules have
  the ability to direct the
  assembly of proteins that
  build the body.
§ This genetic protein
  assembly can be turned
  on and off by the
  environment, or by other
§ Any trait we see is a
  result of the complex
  interactions of many
  genes and countless
  other molecules.
Next step for behavior geneticists:
Controlling Variables
                  Can we design an
             experiment to keep genes
               constant and vary the
             environment and see what

              Or vary the genes in the
               same environment?
Fraternal and Identical Twins
                                          Twin and
Fraternal “twins” from separate eggs      Adoption Studies
are not any more genetically alike than   To assess the
other siblings.                           impact of nature
                                          and nurture, how
                                          do we examine
                                          how genes make a
                                          difference within
                                          the same
 Identical twin: Same sex only            §study traits of
                                          siblings vs.
                                          identical twins
                                          §see if the siblings
                                          vary more than
 Fraternal twin: Same or opposite sex
Identical vs. Fraternal Twins
                                           Twin and
Studies of twins in adulthood show         Adoption Studies
that identical twins are more alike than   How do we find
fraternal twins in:                        out how the same
                                           genes express
§personality traits such as                themselves in
extraversion (sociability) and             different
neuroticism (emotional instability).
                                           We can study the
§behaviors/outcomes such as the rate       traits of identical
of divorce.                                twins as they grow
                                           up, or if they were
§abilities such as overall Intelligence    raised separately
test scores.                               (e.g., the
                                           Minnesota Twin
                                           Family Study).
Studies of Identical Twins Raised Apart
Similarities found in             Critiques of Twin Studies
identical twins despite   •In the more recent years of the
being raised in           Minnesota Twin Family Study, twins
                          have known about each other and may
different homes:          influence each other to be more similar.
§personality, styles of   •Coincidences happen; some randomly
thinking and relating     chosen pairs of people will have similar
§abilities/intelligence   •Environments may be similar; adoptive
test scores               families tend to be more similar than
                          randomly selected families in education,
§attitudes                income, and values.
§interests, tastes
§specific fears
§brain waves, heart       BUT none of these factors explains,
                          better than the genetic explanation,
rate                      why fraternal twins have more
                          differences than identical twins.
Searching for Parenting Effects:
Biological vs. Adoptive Relatives
Studies have been performed with adopted children for
whom the biological relatives are known.
Findings: Adopted children seem to be more similar to
their genetic relatives than their environmental/nurture

            Given the evidence of genetic impact
                on how a person turns out,
              does parenting/nurture
               make any difference?
           Does the home environment have any
              Parenting Does Matter
Despite the strong impact of
genetics on personality,
parenting has an influence
   § religious beliefs
   § values
   § manners
   § attitudes
   § politics
   § habits
How does the interaction of genes
    and environment work?
§ Gene-Environment              Example in
  Interaction: genes turn       animals:
  each other on and off in      shortened daylight
                                triggers animals to
  response to                   change fur color or
  environmental                 to hibernate
§ Epigenetics: The study        Example in
  of how this happens:          humans:
  The environment acts          obesity in adults
  on the surface of genes       can turn off weight
  to alter their activity       regulation genes in
Evolutionary Psychology:
Understanding Human Nature
Some topics:                           Evolutionary
                                    psychology is the
§ Natural selection and                study of how
  adaptation                           evolutionary
§ Evolutionary success may help   principles help explain
  explain similarities                the origin and
                                  function of the human
                                     mind, traits, and

           We have been talking so far
           about human differences; let’s
           now seek insight into the ways in
           which humans are alike.

Evolutionary Psychology:
Natural Selection: How it Works
Artificial Selection
The Domesticated Silver Foxes
                § Dmitri Balyaev and
                  Lyudmila Trut spent
                  40 years selecting
                  the most gentle,
                  friendly, and tame
                  foxes from a fox
                  population, and
                  having those
                § As a result, they
                  were able to shape
                  avoidant and
                  aggressive creatures
                  into social ones, just
                  as wolves were once
                  shaped into dogs.
How might evolution have shaped
the human species?
 §Why does “stranger anxiety”
 develop between the ages of 9
 and 13 months?
    Hint: in evolutionary/survival
    terms, humans are learning to
    walk at that time.
    Infants who used their new
    ability to walk by walking away
    from family and toward a lion
    might not have survived to
    reproduce as well as those who
    decided to stay with parents
    around the time they learned
    to walk.                          19
Evolutionary Psychology’s Explanation of
Biologically Driven Phobias
                    § Why do people so easily
                      acquire a phobia of
                      snakes, more easily than a
                      phobia of cars?
                    § An evolutionary
                      psychologist would note
                      that snakes are often
                      …so, those who more
                      readily learned to fear
                      them were more likely to
                      survive and reproduce.
Critiquing Evolutionary Psychology

       “You’re just
      taking current                “You’re
        reality and             attributing too
      constructing a            much to genes
      way you could            rather than the
      have predicted           human ability to
         it.” This is            make choices
         hindsight               about social
      reasoning and               behavior.”

 Response: yes, but there   Response: yes, but our
 are predictions made       evolutionary past does
 about future behavior      not prevent our ability to
 using this reasoning.      act differently; “is” does
                            not equal “ought.”
                                     Possible areas of
Evolution: Theory                    consensus, with or
                                     without evolution:
§ Evolution is a scientific theory   §The human mind
                                     and body seems
  (NOT a “guess” and not a           almost “designed,” by
  hypothesis, but something          evolution or other
  more): a coherent set of           forces, to have
  principles that fits very well     certain traits and
  with the accumulated evidence.     abilities.
§ Parts of the evolutionary story    §Nurture may shape
  may conflict with other stories    us, but we seem to
  of origins and change over time.   start out with some
                                     sort of human nature.
§ Is there room for overlap and

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