This document discusses the nature vs nurture debate around factors that influence human behavior. It explores how both genetics and environment play a role, using examples from twin studies and research on genes, test scores, success, and stress response. A key point is that a new field of epigenetics has shown that environment can modify genes through chemical tags, turning some on or off, meaning nature and nurture have a more complex interaction than previously understood. Overall, the document aims to show that both genetics and life experiences influence human behavior in complex ways.

1. Genetics
& Nature vs. Nurture

2. Nature vs. Nurture
Is there a biological reason why girls tend to like dolls and
clothes? Is there a biological reason why boys tend to like toy
cars and guns? Or is this something that children are nurtured
to like by their parents and other societal factors?

3. Nature vs. Nurture
Why are women less interested in certain jobs? Is it because of
their genes, hormones, or biology? Or is it because they are
nurtured into certain career paths by friends, parents, movies,
media, and other societal factors?
Careers with Many Women:
Nurses
Secretaries
Preschool/Kindergarten Teachers
Flight Attendants
Waitresses
Social Workers
Careers with Few Women:
Surgeons
Computer Programmers
Chefs
Firefighters
Aircraft Pilots
Engineers

4. Nature vs. Nurture Debate
Nature:
Our genetics
determine our
behavior. Our
personality traits and
abilities are in our
“nature.”
Nurture:
Our environment,
upbringing, and life
experiences determine
our behavior. We are
“nurtured” to behave
in certain ways.

5. Nature vs. Nurture Debate
Nature:
We genetically inherit
physical traits from our
parents, but we also
inherit personality traits,
intelligence, and
preferences.
Nurture:
The household and city we
grew up in, how we were
raised by our parents,
teachers, and friends -
these are environmental
factors that determine
who we are.

6. Nature vs. Nurture Debate
A Point for Nature:
“Studies show that
we inherit genes that
are related to certain
personality traits.”
A Point for Nurture:
“Often Identical twins
grow up to have
very different
personalities and
preferences.”
?

7. Nature vs. Nurture Debate
Today we know that nature and nurture
BOTH help shape our behavior.The question
for today’s debate is this:
Which one has the GREATER influence on
human behavior?

8. Pair-Share
Do you think you share any personality traits
with your parents or grandparents?

9. Behavioral Genetics:
The study of the effects of heredity on behavior.
Behavioral genetics tries to answer this question:
To what extent are our abilities, personality traits, sexual
orientations, sociability, and psychological disorders
determined by genes inherited from our parents?
Will this
child be
more like
her birth
parents or
adoptive
parents?

10. Twin Studies
Twin Studies are used to help us answer the question of “nature
vs. nurture.” Because identical twins share the same genetic
makeup, we can assume that differences between them are due
to environmental factors.

11. Twin Studies
Pair 1:
Same DNA
Same Environment
However, twins often grow up in
very similar environments.
If intelligence is the same, it’s hard
to tell if it is due to genetics or
environment.
Pair 2:
Same DNA
Same Environment
If intelligence is different, we can
assume that there are tiny
differences in environment (different
friends, time spent studying, etc.)
that caused the difference.

12. Twin Studies
Pair 4:
Different DNA
Same Environment
One sibling is adopted.
If intelligence is the same,
it is likely due to environment.
If intelligence is different, it is
likely due to genetics.
Pair 3:
Same DNA
Different Environment
Twins adopted by different families
grow up in different environments.
If intelligence is the same, it is likely due
to genetics. If intelligence is different,
it is likely due to environment.

13. Twin Study Results?
Extraverted
Neurotic
Agreeable
Conscientious
Correlation (How strongly twins shared the same traits)
0 0.1 0.2 0.3 0.4 0.5
Identical Twins (99% DNA match) Fraternal Twins (50% DNA match)
Open to New
Experiences

14. Pair-Share
Do you think a Twin Study is a reliable way to
test whether our behavior is determined more
by nature (genetics) or nurture (environment)?
Why or why not?

15. What do studies tell us?
Study: 1,252,387 genetic
markers were tested for
association with personality
traits.The results indicated
that only 1% of genetic
variants significantly
contribute to personality
variation.This means our
individual genetic differences
do not significantly contribute
to personality trait variation.
(Verweij et al., 2010)
Personality:

16. What do studies tell us?
Study: 1,252,387 genetic
markers were tested for
association with personality
traits.The results indicated
that only 1% of genetic
variants significantly
contribute to personality
variation.This means our
individual genetic differences
do not significantly contribute
to personality trait variation.
(Verweij et al., 2010)
This was NOT a twin
study: it was a genome-
wide association study
done in 2010.This is
where each person gives
a sample of DNA, from
which millions of genetic
variants are read in order
to see if certain genes are
associated with diseases
or personality traits.

17. Other Studies
That relate to the “nature, nurture” question
Study: Men who carry one or two
extra copies of a gene called allele 334
often behave differently in relationships
than men who lack this gene variant.
Men with an extra copy of the gene felt
a weaker, less permanent attachment
to their partners, and were more likely
to be unfaithful. Men who had two
copies of allele 334 were also twice as
likely to have had a marital or
relationship crisis in the past year than
those who lacked the gene variant.
(Karolinska Medical Institute, Stockholm).

18. Nature? (Genetics) or Nurture? (Environment)
Study:
Novelty-seeking
behavior (impulsive
decision-making, the
need to explore, lack
of organization) is
related to the
presence of a certain
gene in the body, and
is highly inheritable.
(Golimbet et al., 2007).
Other Studies
That relate to the “nature, nurture” question

19. Genes & Test Scores
In a recent study at University college London, researchers
compared test scores of high school students to their genes.
The study found that 58% of the variation on student test
scores was due to genetic factors.
The research drew
on the exam scores
of more than 11,000
16-year-olds.
Researchers also
compared the scores
of identical and non-
identical twins in a
supplementary study.

20. Genes & Success
Does having amazing genes lead to future
career success and wealth?
This boy had genius
parents.
Do you think his genes
will have a greater
impact on his life, or his
environment?

21. Genes & Success
Studies show that for children living
in poverty, it did not matter whether
they had good genes or not.The
negative impact of the environment
almost always played a greater role
in their future success than their
genes.
For children in middle class and
wealthy homes, having good genes
became very important to
determining their future success.
Genes played a much greater role in
the future success of each child.

22. Genes & Success
Researchers concluded that for children in harsh living
conditions, it is harder for exceptional genes to “shine through.”
(EricTurkheimer, 2003)

23. Feral Children
Feral Children
are those who
lived away from
human contact
from a very
young age, and
have little or no
experience of
human care,
loving or social
behavior, or
human language.

24. Feral Children
Homework:
Investigate it yourself:
What can we learn from Feral
Children about nature vs.
nurture?
Research at least one feral child,
and write a paragraph (at least 5
sentences) about what feral
children can teach us about
nature vs. nurture.
Submit by sharing a google doc
with Ms. G before the start of
our next class.
Examples:
Genie Wiley
Oxana Malaya
Kamala & Amala
Prava the Bird Boy
…

25. Nature
vs.
Nurture:
Epigenetics

26. Epigenetics is a
new field showing
us that
environment can
modify our genes!

27. Epigenetics
This is a new branch of genetics that is shedding light
on the “nature vs. nurture” debate.
“Epi” means “above” or “on top of” so epigenetics refers to
modifications that occur on top of your genes. Environmental
factors actually cause your cells and genetic code to change
over your lifetime. Your genetic code itself is always the same,
but genes can be “turned on” or “turned off.”
For example, your diet can cause
“epigenetic changes” to your DNA.

28. Epigenetics
different clothing styles.Their personalities became different: "Mary
is more conscientious about what she does. I am more confident.
That became increasingly obvious as the years went by," says
Barbara. Mary developed depression, Barb did not. Mary was girly
and feminine, Barbara was more of a “tomboy.”
HERES WHAT HAPPENED TO THEIR GENES…
Mary and Barbara are identical
twins raised in the same family.
When they were kids, their parents
treated them the same and they
had similar interests and
personalities. However, the older
they became, the more different
they became.They dressed in

29. Epigenetics
The DNA of the twins began the same, but over the course of
their lives, different health choices and environmental stimuli
caused the DNA code to change.

30. Epigenetics
This is a strand of DNA.
DNA is a long, ladder-shaped
molecule: the famous ‘double-helix’
shape. Inside our cells, DNA
contains all the information needed
to make us grow and live.

31. Epigenetics
Genes are short sections or
“chunks” of DNA.
They act as a set of
instructions for our
cells, telling them how
to build our bodies.

32. Epigenetics
Throughout your life, and
depending on specific
conditions, a chemical called
methyl attaches to genes.
This chemical “switches” on
or off only a selection of
your genes.
This process is known
as gene regulation.

33. Epigenetics
These chemical methyl
attachments are called
epigenetic
tags.

34. Epigenetics
These chemical methyl
attachments are called
epigenetic
tags.
Think of them like
switches that turn certain
genes on or off, making
them active or inactive.

35. Epigenetics
Your lifestyle
determines which
genes get “switched
on” or “switched off.”
What (and how much) you eat, how
much you exercise, if you smoke, if
you get a disease, if you experience
high stress, if you are exposed to
chemicals, etc…can all impact the way
your genes are expressed.

36. Epigenetics
During fertilization,
mom & dad’s DNA
mixes in the egg.
During the first days
after fertilization, the
epigenetic tags are
erased…mostly.
A small number of
tags remain on the
offspring’s DNA.

37. Epigenetics
Because a small number
of tags remain on the
offspring’s DNA…
…these are called
“imprinted
genes.”

38. Epigenetics
Thus, the environment
and lifestyle choices of
the parents actually
modified the genetic
code of their offspring.

39. Stress Gene Experiment
Experimental Group 1:
Baby rats are nurtured
by a mother rat
Experimental Group 2:
Baby rats are neglected
by a mother rat
?

40. Stress Gene Experiment
Group 1:
The babies’ DNA is tested
and epigenetic tags are
visible on the stress
response gene, turing it
“on.” These rats respond
very well in stressful
situations for the rest of
their lives.
Group 2:
The babies’ DNA is tested
and epigenetic tags are
NOT present on the stress
response gene, keeping it
“off.” These rats do NOT
respond well in stressful
situations for the rest of
their lives.

41. Stress Gene Experiment
Group 1:
The offspring of these rats
ALSO have epigenetic tags
on the stress response
gene: the babies inherit an
imprinted gene on which
the stress response gene is
“turned on.”
Group 2:
The offspring of these rats
ALSO have NO epigenetic
tags on the stress response
gene.Thus, these babies do
not respond well to stress
because their PARENTS
were not nurtured by a
mother rat.

42. Inherited Stress Tolerance?
The rats that were not nurtured as
babies had the stress response gene
“turned off.” In this case, the rats
could not handle stressful situations
well for the rest of their lives.They
also passed this inability to respond to
stress to their children.
This study shows that attentive, loving parents set their
children (and grandchildren!) up for future success by
creating an epigenetic modification that allows the children
to better cope with stress. The environment can change our
genes, and our genes impact certain aspects of our behavior.

43. Are Epigenetic Changes Permanent?

44. Epigenetics
Q: What does this mean for the nature vs. nurture debate?
(1)That we are not defined by our genes. Our lifestyle choices can
actually impact our genetic codes, causing certain genetic traits to
express themselves more or less strongly.
(2)That the interaction between nature and nurture is WAY more
complicated than we ever imagined. Genes and environment are
always working together.
This does not mean that we have the power to change all of our
genes! Some genes are not modifiable, meaning that epigenetic tags
do not affect those genes.