Transcript Behavior Genetics

The History of
Behavior Genetics
How nature affects our genetics and
how our genetics change how we
perceive and deal with our environment.
Leaving evolutionary and entering
biological genetics…
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evolutionary psychologists : universal
human tendencies
behavior geneticists : differences in one
another
What is the relationship?
Sir Francis Galton
Sir Francis Galton, inspired
by his cousin Darwin's Origin
of Species (1859), pioneered
the field of behavioral
genetics.
 Galton believed all human
traits, including behavior, are
solely determined by genes,
without any contribution from
the environment.
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Sir Francis Galton
Founder of Eugenics
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This idea became the basis for
eugenics, a term Galton coined in
1883 to describe the use of genetics
for social planning.
Galton, in other words, believed that
selective "breeding" of the human
species could guarantee that the
"best" traits would remain in the
human population while the "worst"
traits could be eliminated.
Sir Francis Galton
Founder of Psychometrics
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Psychometrics is the field of study
(connected to psychology and statistics)
concerned with the measurement of
"psychological" aspects of a person such as
knowledge, skills, abilities, or personality.
Critics, including "hard science" practitioners
and social activists, have argued that such
definition and quantification is impossibly
difficult and that such measurements are very
often misused.
This is What can Happen When Bad
People Hear Good Ideas
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Based on Galton's ideas, the eugenics movement built
momentum in the United States, where between 1905 and
1933, several states based laws and legal decisions on
eugenics theory, and the federal government heavily restricted
immigration from Eastern and Southern Europe.
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The Johnson Act limited immigrants from each country according to
their proportion in the U.S. population in 1890 — a time prior to the
major waves of southern and eastern European immigration when the
U.S. was decidedly more Anglo-Nordic in composition.
This is What can Happen When Bad
People Hear Good Ideas
The goal was the production of a
genetically "pure" American
population.
 During this time in American history,
criminals, people with low IQs and, in
some cases, even women who had
illegitimate children, were sterilized.
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This is What can Happen When
Bad People Hear Good Ideas
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During its time in power, the government
of Nazi Germany staunchly supported and
enforced the principles of eugenics.
Eugenics-based legislation culminated in
the "euthanasia" of the mentally retarded
and the physically disabled, who,
according to Nazi geneticists, would
otherwise contaminate the German people
with unfit genes.
A Swing Back in the Other Direction
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It was not until the 1980s that the scientific
community began to pay serious attention
to behavioral genetics as a science.
Using gene manipulation technologies
which had been in the works since the late
1960s, geneticists could finally map the
human genome itself.
A Swing Back in the Other Direction
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Since the early ’80s,
geneticists have identified
genes for cystic fibrosis,
muscular dystrophy, and
Huntington's disease.
The successes in
identifying and mapping
human disease genes
have revitalized interest in
identifying genetic factors
underlying behavioral
traits.
Nature, Nurture and Human
Diversity
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Behavior Geneticists study our differences
and weigh the relative effects of heredity
and environment.
Differences
Brain: Asymmetry of brain across genders
 Biology: May change during development
 Genes: Genetic anomalies
may make us different
 Behaviour: speak different languages
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Similarities
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Genes: Same set of Chromosomes
Biology: The organs and body function the
same
Brain: Same brain Architecture
Behaviors: Speak language
Genes: Our Code of Life
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In the nucleus of a cell chromosomes
containing DNA (deoxyribonucleic acid)
are situated.
Segments within DNA constitute genes
making proteins to determine our
development.
Genome
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Genome is the set of complete instructions
for making an organism containing all the
genes in that organism. Thus human genome
makes us human and the genome for
drosophila makes it a common house fly.
The Two Main Tools of a Behavior
Geneticist:
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The Goal: Behavior Geneticists must try to
untangle the mystery between the influence
of genetics (nature) and the environment
(nurture).
The Tools:
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Twin Studies
Adoption Studies
Types of Twins
Identical
twins
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Fraternal
twins
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Same
sex only
Same or
opposite sex
(Identical Twins) Monozygotic
twins develop when a single egg
is fertilized by a single sperm and
at some stage in the first two
weeks the developing embryo
splits in two, with the result that
two, GENETICALLY IDENTICAL
babies develop.
(Fraternal Twins) Dizygotic twins
occur when two separate eggs
are fertilized by two different
sperm. These two fertilized eggs
then develop independently.
Dizygotic twins share the same
type of genetic relationship as
non-twin siblings, hence the term
fraternal.
Two placental arrangements in identical twins
Separated Twins
A number of studies have looked at identical
twins raised separately from birth or close there
after and have found a number of similarities.
 Interests, Fears
 Brain Waves, Heart Rate
 Abilities, Attitudes
 Personality, Intelligence
 Brain Waves, Heart Rate
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Separated Twins
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Critics of separated twin studies note that
such similarities can be found between
strangers.
However, researchers point out that
differences between fraternal twins are
greater than identical twins.
Adoption Studies
Opposed to twin studies, adoption studies
suggest that adoptees (who may be
biologically unrelated) tend to be different
from their adoptive parents and siblings.
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Adoptive Studies
Adoptive studies strongly point to the simple
fact that biologically related children turn out to
be different in a family. So investigators ask:
 Do siblings have differing experiences?
 Do siblings, despite sharing half of their
genes, have different combinations of the
other half genes?
 Ultimate question: Does parenting have an
effect?
Parenting
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Parenting does have an effect on
biologically related and unrelated
children.
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Faith, Politics
Manners, Beliefs
Attitudes, Values
Parenting Influences
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Behavior Genetics
Vocabulary
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Behavior Genetics
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study of the power and limits of genetic and
environmental influences on behavior
Environment
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every nongenetic influence, from prenatal
nutrition to the people and things around us
Behavior Genetics
Vocabulary
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Temperament
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a person’s characteristic emotional
reactivity and intensity
Heritability
the proportion of variation among
individuals that we can attribute to genes
 may vary, depending on the range of
populations and environments studied
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Group Differences
If genetic influences help explain individual
diversity in traits, can the same be said
about group differences?
 Not necessarily. Individual differences in
weight and height are heritable and yet
nutritional influences have made westerners
heavier and taller than their ancestors a
century ago.
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Nature and Nurture
Some human traits are fixed, like having two
eyes, most psychological traits are liable to
change with environmental experience.
So genes provide choices to the organism to
change its form or traits when environmental
variables change. Therefore genes are pliable
or self‐regulating.
Gene-Environment Interaction
Genes can influence traits which affect
responses, and environment can affect gene
activity.
 A genetic predisposition that makes a child
restless and hyperactive, evokes angry
responses from his parents. A stressful
environment can trigger genes to manufacture
neurotransmitters leading to depression.
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Molecular Genetics: Promises and
Perils
Molecular geneticists are trying to identify
genes that put people at risk for disorders. With
this kind of knowledge parents can decide to
abort pregnancies where fetuses are suspected
of having such disorders .But this opens up a
real concern about ethical issues involving such
choices.
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