1. Genetics, Evolutionary Psychology, and Behavior
Module 6
Genetics, Evolutionary Psychology, and Behavior

2. Genetics, Evolutionary Psychology, and Behavior Behavior Genetics: Predicting Individual Differences
6-1: WHAT ARE CHROMOSOMES, DNA, GENES, AND THE HUMAN GENOME? HOW DO BEHAVIOR GENETICISTS EXPLAIN OUR INDIVIDUAL DIFFERENCES?
Environment: Every nongenetic influence, from prenatal nutrition to the people and things around us
Heredity: The genetic transfer of characteristics from parents to offspring
Behavior genetics: Study of the relative power and limits of genetic and environmental influences on behavior

3. Genetics, Evolutionary Psychology, and Behavior Behavior Genetics: Predicting Individual Differences Genes: Our Codes for Life
Chromosomes: Threadlike structures made of DNA molecules that contain the genes
DNA (deoxyribonucleic acid): Complex molecule containing the genetic information that makes up the chromosomes
Genes: Biochemical units of heredity that make up chromosomes; segments of DNA capable of synthesizing proteins
Genome: All the genetic material in an organism’s chromosomes
When genes are expressed, they provide the code for creating the proteins that form our body’s building blocks
The nucleus of every human cell contains chromosomes, each of which is made up of two strands of DNA connected in a double helix. Genes are DNA segments that, when expressed (turned on), direct the development of proteins that influence a person’s individual development.

4. Genetics, Evolutionary Psychology, and Behavior Behavior Genetics: Predicting Individual Differences Twin and Adoption Studies
6-2: HOW DO TWIN AND ADOPTION STUDIES HELP US UNDERSTAND THE EFFECTS AND INTERACTIONS OF NATURE AND NURTURE?
Identical Versus Fraternal Twins
Identical (monozygotic) twins: Develop from a single fertilized egg that splits in two, creating two genetically identical organisms
Identical twins share the same conception and uterus, and usually the same birth date and cultural history

5. Genetics, Evolutionary Psychology, and Behavior Behavior Genetics: Predicting Individual Differences Twin and Adoption Studies
Same fertilized egg, same genes; different eggs, different genes. Identical twins develop from a single fertilized egg, fraternal from two.

6. Genetics, Evolutionary Psychology, and Behavior Behavior Genetics: Predicting Individual Differences Twin and Adoption Studies
Identical Versus Fraternal Twins
Fraternal (dizygotic) twins: Develop from separate fertilized eggs
Genetically no closer than brothers and sisters, but they share a prenatal environment
Studies of twins in adulthood show that identical twins are more alike than fraternal twins in:
Having disorders, such as autism spectrum disorder
Personality traits such as extraversion (sociability) and neuroticism (emotional instability).

7. Genetics, Evolutionary Psychology, and Behavior Behavior Genetics: Predicting Individual Differences Twin and Adoption Studies
Separated Twins
Similarities found in identical twins despite being raised in different homes:
Personality, styles of thinking and relating
Abilities/intelligence test scores
Attitudes
Interests, tastes
Specific fears
Brain waves, heart rate

8. Does the home environment have any impact?
Genetics, Evolutionary Psychology, and Behavior Behavior Genetics: Predicting Individual Differences Twin and Adoption Studies
Biological Versus Adoptive Relatives
Studies conducted with adopted children for whom the biological relatives are known
Adopted children seem to be more similar to their genetic relatives than their adoptive relatives
The environment shared by a family’s children has virtually no discernible impact on their personalities.
Does the home environment have any impact?

9. Genetics, Evolutionary Psychology, and Behavior Behavior Genetics: Predicting Individual Differences Twin and Adoption Studies
Biological Versus Adoptive Relatives
Despite the strong impact of genetics on personality, parenting has an influence on:
Religious beliefs
Values
Manners
Attitudes
Politics
Habits

10. Genetics, Evolutionary Psychology, and Behavior Behavior Genetics: Predicting Individual Differences Gene-Environment Interaction
6-3: HOW DO HEREDITY AND ENVIRONMENT WORK TOGETHER?
Genes and environment–nature and nurture–work together
Genes are self-regulating; rather than acting as blueprints that lead to the same result no matter the context, genes react
Genes and experience interact
Epigenetics: The study of environmental influences on gene expression that occur without a DNA change

11. EPIGENETICS INFLUENCES GENE EXPRESSION
Life experiences beginning in the womb lay down epigenetic marks—often organic methyl molecules—that can affect the expression of any gene in the associated DNA segment. (From Champagne, 2010.)

12. Genetics, Evolutionary Psychology, and Behavior Evolutionary Psychology: Understanding Human Nature
6-4: HOW DO EVOLUTIONARY PSYCHOLOGISTS USE NATURAL SELECTION TO EXPLAIN BEHAVIOR TENDENCIES?
Behavior genetics explore the genetic and environmental roots of human differences.
Evolutionary psychologists instead focus mostly on what makes us so much alike as humans.

13. Genetics, Evolutionary Psychology, and Behavior Evolutionary Psychology: Understanding Human Nature
Evolutionary psychology: The study of the evolution of behavior and the mind, using principles of natural selection.
Evolutionary psychologists use Charles Darwin’s principle of natural selection to understand the roots of behavior and mental processes
Natural selection: The principle that those chance inherited traits that better enable an organism to survive and reproduce in a particular environment will most likely be passed on to succeeding generations
Nature has indeed selected advantageous variations from the new gene combinations produced at each human conception plus the mutations (random errors in gene replication) that sometimes result. But especially in humans, genes and experience together wire the brain.

14. Genetics, Evolutionary Psychology, and Behavior Evolutionary Psychology: Understanding Human Nature Natural Selection and Adaptation
Natural selection and adaptation
Genes selected during our ancestral history give us a great capacity to learn and therefore to adapt to life in varied environments.
The tight genetic leash that predisposes a dog’s retrieving, a cat’s pouncing, or a bird’s nesting is looser in humans.
Adaptive flexibility in responding to different environments contributes to the ability to survive and reproduce.

15. Evolutionary Psychology: How Natural Selection Works
Begin with a species’ genome, which contains a variety of versions of genes that shape traits.
Conditions make it difficult for individuals with some traits (some versions of those genes) to survive long enough to reproduce.
Other individuals thus have their traits and genes “selected” to spread in the population.

16. In what ways might this be problematic?
Genetics, Evolutionary Psychology, and Behavior Evolutionary Psychology: Understanding Human Nature Evolutionary Success Helps Explain Similarities
Our Genetic Legacy
As success-enhancing genes were selected over time, behavioral tendencies and thinking and learning capacities emerged that prepared our Stone Age ancestors to survive, reproduce, and send their genes into the future.
As inheritors of this prehistoric genetic legacy, we are genetically predisposed to behave in ways that promoted our ancestors’ surviving and reproducing, ways that may be mismatched with our contemporary lifestyle.
In what ways might this be problematic?

17. Genetics, Evolutionary Psychology, and Behavior Evolutionary Psychology: Understanding Human Nature Evolutionary Success Helps Explain Similarities
Evolutionary Psychology Today
Darwin’s theory of evolution has become one of biology’s organizing principles
The theory lives on in the second Darwinian revolution, the application of evolutionary principles to psychology
Darwin anticipated this, foreseeing “open fields for far more important researches. Psychology will be based on a new foundation.”