Biological Bases of Behavior

3C: Genetics, Evolutionary Psychology, and Behavior

Genes: Our Codes for Life Total of 46 chromosomes-threat like

structures made of DNA molecules that contain genes› 23 from mom and 23 from dad› DNA: contains genetic information› Genes: biochemical units of heredity› Book example

Genes: Our Codes for Life

Genes can be active or inactive Environmental events “turn on” genes

› When turned on, they provide the building blocks of physical development

Human genome: common human DNA› Share 96% of our DNA with Chimps

Most of our traits are influenced by many genes› Physical to Intelligence› https://www.youtube.com/watch?

v=ubq4eu_TDFc

Twin and Adoption Studies Identical: develop from a single fertilized

egg that splits in two genetically identical› Share same genes, but may vary on the

number of copies of those genes› Some are mirror images of each other: left vs

right hand or have different personalities Fraternal: develop from separate fertilized

eggs https://www.youtube.com/watch?

v=Trc2dJgeyvc

Separated Twins

Read Case Studies page 97-99 Conclusions based on the reading? What do we need to be careful about

regarding separated identical twin studies?

Separated Twins

They continued to find similarities not only to taste and physical attributes but also of personality, abilities, attitudes, interests, and even fears

Remarkable similarities in life choices, support the idea that genes influenced personality

Greater appreciation of genetic influences Don’t over generalize! https://www.youtube.com/watch?

v=0yTCShemS_0

Biological vs. Adoptive Relatives

Parents vs. Adoptive Parents Hereditary shapes personality

› Adoptees more similar to biological parents in personality than adoptive parents

However, parents due influenced their child’s attitudes, values, manners, faith, and politics

Most adoptive children thrive› Self-giving parents: children become more self-

giving, score higher on intelligence tests than biological parents

Heritability

The extent to which variation among individuals can be attributed to their differing genes. Rather it explains that 50% of the observed variation among people

Just because a trait is heritable does not mean it will affect an individual

We can never say what % of an individual's personality or intelligence is inherited

Group Differences and Heritability

Individual differences in height and weight are highly heritable yet nutritional rather than genetic

Heritable individual difference need not imply heritable group differences› Ex: Putting people in a new social context

can change their aggressiveness

Gene-Environment Interaction

Environment triggers gene activity Genetically influenced traits evoke

significant responses in others We select environments suited to our

natures Think nature via nurture

The New Frontier: Molecular Genetics

Molecular Genetics: identify specific genes influencing behavior

Goal is to find some of the genes that influenced normal human traits such as body weight, sexual orientation, personality, and mechanism that control gene expression

The New Frontier: Molecular Genetics

Genetics tests can reveal at-risk populations for many diseases

Medical personnel are able to provide parent with a readout on how their fetus gene’s differ from the normal patter› Double-edged sword? Problems?

Discrimination?

Evolutionary psychology: Understanding Human Nature

Focus on what makes humans so a like and use Darwin’s theory on natural selection to understand the roots of behavior and mental processes

Natural Selection and Adaptation

Darwin When certain traits are selected by

reproduction those traits will prevail Genes allow us with a great capacity to

learn and adapt to life in varied environments

Evolutionary Success Help Explains Similarities

Shared human traits shaped by natural selection

Shared human genome Outdated tendencies: crave sweets and

fats

An Evolutionary Explanation of Human Sexuality

Gender differences in sexuality Natural Selection and Mating

preferences› Ancestral History: Women more relational,

choosing wisely Men more recreational, pairing widely

› Today: Women attracted to more mature, bold, dominant, affluent. Men youthful/fertile appearance (WHY?)

Critiquing the Evolutionary Perspective

What’s considered attractive does vary time and place

Cultural expectations can bend genders

Social expectations and mate preferences

How we came to need does not dictate how we ought to be