PSY 230 Main Page

Chapter 3:

Biological  Beginnings 

The Evolutionary Perspective 

•         Natural selection is evolutionary process

–        Based on Darwin’s theory

–        Best-adapted members of species survive to reproduce

–        Survival characteristics passed on in genes

–        Ideas explain behavior in evolutionary psychology approach

–        David Buss: evolution shapes our physical features and how we make life decisions 

•         Evolutionary developmental psychology:

–        Extended juvenile period allows brain to develop and learn complexity of social interactions

–        Many aspects of childhood are preparation for adulthood evolving over time

–        Some childhood characteristics promote adaptation during development before reaching adulthood

–        Many evolved psychological mechanisms are domain-specific or specific to environmental needs

–        Evolved mechanisms are not always adaptive in contemporary society 

•         Currently:

–        There is great interest in evolutionary explanations of aging

–        Natural selection has not weeded out harmful conditions or diseases and nonadaptive characteristics associated with reproduction

–        Evolutionary psychology approach has its limitations and weaknesses, and its critics 

Genetic Foundations 

•         Genetic process:

–        Human life begins as a single cell

–        Nucleus of each cell contains DNA

–        DNA carries genetic information in double-helix

–        Genes are units of hereditary information in each chromosome

–        Human Genome Project mapped the  
human genome and found that it included
only about 30,000 genes  

•         All cells in human body (except the sperm and egg) have 46 chromosomes arranged in 23 pairs

•         Meiosis forms sperm and eggs (gametes)

•         Fertilization: fusing of sperm and egg to form one set of paired chromosomes (offspring gets half of its genes from each parent)

•         Child’s sex determined by 23rd pair of chromosomes 

•         Genotype: a person’s genetic material containing

–        Phenotypes: observable or physical characteristics such as height, body style and psychological characteristics like personality and intelligence

–        Dominant genes in each pair have the most influence on characteristics unless the pair contains two recessive genes which will
have a dominant effect 

•         Sex-linked genes:

–        X-linked diseases and mutations such as hemophilia and fragile-X syndrome

–        Females have a second X chromosome so chances of having mutation or disease are less, BUT they are carriers of it

–        Males have no second chance; more males than females have X-linked diseases  

•         Chromosome abnormalities usually arise in meiosis when chromosomes do not properly separate 

•         Sex-linked abnormalities:

–        Klinefelter syndrome: males born with XXY mutation instead of XY

–        Fragile X syndrome: occurs more often in males than females; X chromosome constricted or breaks off

–        Turner syndrome: females born with XO rather than XX, sometimes causing infertility

–        XYY syndrome: males with extra Y chromosome 

•         Gene-linked abnormalities:

–        PKU: occurs in 1 out of 10,000-20,000 births but can be treated if detected
early enough

–        Sickle-cell anemia: impaired red blood cells die more quickly; more often found in African Americans

–        Other abnormalities: cystic fibrosis, diabetes, spina bifida, Huntington disease, and Tay-Sachs disease 

Reproductive Challenges and Choices 

•         Prenatal diagnostic tests:

–        Amniocentesis: samples amniotic fluid

–        Ultrasound sonography: high frequency sound waves used

–        Chorionic villus sampling: small sample of placenta is removed during 8th–11th week

–        Maternal blood test 

•         Infertility and reproduction technology:

–        In vitro fertilization: egg and sperm united in laboratory dish

–        Gamete intrafallopian transfer: egg and sperm deposited directly into fallopian tube

–        Zygote intrafallopian transfer: eggs fertilized in lab then zygote deposited into fallopian tube 

•         Consequences of multiple births:

–        Higher risks of life-threatening problems

–        Health risks to mother

–        Psychological effects on children 

•         Another alternative: adoption 

•         Childrearing challenges after adoption:

–        Infancy: attachment?

–        Early childhood: integration into family

–        Middle and late childhood: curiosity about real/biological parents

–        Adolescence: child’s reflection on adoptive status 

Heredity, Environment, and Individual Differences 

•         Heredity and environment interact to produce development; each person’s development varies  

•         Behavior genetics:

–        Most research based on twin and adoption studies

–        Twin studies compare identical (monozygotic) twins with fraternal (dizygotic) twins

–        Adoption studies compare child’s traits with those of adoptive and biological parents

–        All studies conducted in developed countries only 

•         Genotype–environment correlations:

–        Intelligent biological parents who like to read provide books and encouragement for child to read – likely outcome is skilled reader

–        Active, smiling, cooperative, and attentive child gets more pleasant, encouraging responses from adults than passive, quiet child

–        Some children actively seek out aspects of their environment that enhance their ability to excel 

•         Siblings’ shared and nonshared environmental experiences analyzed 2 ways

–        Shared examined as common experiences like family SES, parental personalities, and neighborhood 

–        Nonshared examined as child’s unique experiences inside & outside family not shared by siblings

•         Personal relationship with each parent

•         Friends and classmates

•         Teachers and other influential adults

•         “Niches” sought out due to unique personality traits (musical/artistic abilities) 

•         Epigenetic view: development is an ongoing, bidirectional interchange between heredity/genetics and environment

–        Example: baby has inherited genes but is exposed to toxins during prenatal development

–        Outcome can change genetic development during the prenatal or infancy period