Nature vs. Nurture

Genes: Codes for Life • 46 chromosomes: 23 from mother, 23 from father • Chromosomes make up our coiled molecule called: DNA (deoxyribonucleic acid) • 20,000 genes which are active (expressed) or inactive • At a genetic level, Chimpanzees and humans are 96% identical Genetics § Chromosome § Threadlike structures made of DNA molecules that contain genes § DNA § A complex molecule containing the genetic information that makes up the chromosome § Genes- Unit of heredity (transmitted in a discrete form) Adapted from Dr. Rios GENETICS •Genes can give us a lot of information • Color of hair/eyes • Disabilities • Ancestor origins Adapted from Dr. Rios Genetic disorders •Chromosomal problems •Cystic fibrosis •G6PD Deficiency •Muscular Dystrophy •Down Syndrome Adapted from Dr. Rios Twin Studies • Identical twins (single fertilized egg) • Fraternal twins (two separate fertilized eggs) • Researchers have found that separated twins often share similarities not just in tastes and physical attributes but in personality, abilities, attitudes, interests, and fears STUDIES ON TWINS • Minnesota Twin Family Study • Over the course of 20 years, studied 137 pairs of twins • 1979 – 1999 • Overall Results • Genes play a larger role than we thought • Posture • Health Adapted from Dr. Rios Biological versus Adoptive Relatives • Studies of hundreds of adoptive families have found, people who grow up together (that are not identical twins) do not resemble one another in personality (McGue & Bourchard, 1998) • Personality traits such as extraversion and agreeableness are found to be much more closely liked to biological parents • Genetic disposition may override environmental influences Temperament and Heredity • Temperament: emotional reactivity and emotional intensity • Temperament tends to typically persist • Emotionally intense preschoolers tend to become relatively emotionally intense young adults (Larsen & Diener, 1987) Heritability • Heritability: Mathematical estimates of the extent to which variation among individuals in a group can be attributed to their differing genes • This does not give x% is due to genes and y% due to environment • Gives a percentage of the extent to which differences between two people can be accounted for by the genetic makeup • Personality traits: 40% • Major Depressive disorder: 30% • Intelligence: 50-80% • Autism: 90% Heredity • Environment become more similar, heredity becomes the primary source of differences • Similar heredities but raised in drastically different environments, heritability would be much lower • Heritability is not a single-fixed score Gene-Environment Interaction • Epigenetics: Environments triggering or blocking genetic expression • Genes are self-regulating • African butterfly that turns green in the summer and turns brown in the fall is due to a temperature-controlled genetic switch • Environmental factors can affect the epigenetic molecules that regulate gene expression • Possible mechanism why effects of child-hood trauma, poverty, and malnutrition can have lifetime lasting effects, it changes a person’s genetic makeup • US Civil War prisoners and former Holocaust survivors have passed epigenetic gene alterations with their offspring (Costa et al., 2018; Yehuda et al., 2016) Natural Selection and Adaptation • Natural selection: Process in which • Organisms varied offspring compete for survival • Biological and behavioral variations increase organisms’ reproduction and survival changes for a particular environment • Offspring that survive are more likely to pass their genes to the next generation • Populations characteristics change overtime • Evolutionary success explains similarities Evolution-Theory Origins § Charles Darwin- Theory of evolution § Kept careful records of wildlife/fossils (HMS Beagle) § Artificial Selection § Origin of Species (1859) § Natural selection § Interestingly wasn’t the only one! § Alfred Wallace Adapted from Dr. Rios Evolution §Biological Evolution- how changes take place in the characteristics of a population of organisms over time § Changes in a SPECIES over many GENERATIONS §Three Components of Evolution: ①Variation ②Selection ③Retention Adapted from Dr. Rios st 1 Component: Variation § Variation- individual members of a species differ from one another § Each organism is unique § Even within the same species § Differences (variations) between individual organisms § Raw material on which natural selection acts § Evolution can only act on characteristics that ALREADY EXIST Adapted from Dr. Rios nd 2 Component: Selection § Selection (Natural Selection)- environment differentially favors organisms with characteristics that affect survival and production offspring § Organisms best adapted to their environment tend to survive§ They pass on genes § Less adaptive die out § Provides direction to the process Adapted from Dr. Rios Adapted from Dr. Rios Survival of the “Fittest” § “Fitter” does not equal : § “better”, “bigger”, “faster”, or “stronger” necessarily § In Darwin’s time, it meant “appropriate” or “adaptive” § Why aren’t we all superhuman superhero's then!?!? § Species may not evolve to fit environment perfectly § Their adaptations only need to work “well enough” Adapted from Dr. Rios rd 3 Component: Retention §Retention- the favored variations are retained through heredity § Mendel’s research with peas § Factors are passed on unchanged-Not a blend of different characteristics §Selected variations must be retained (kept) (in our genes) § And continue in the “pool” that selection operates on §Without retention- evolution would not be possible Adapted from Dr. Rios Experience and Brain Development • Early experiences leaves impact on our brains • Series of experiments demonstrate that enriched environments versus impoverished environments highly impacts are brain development (Renner & Rosenzweig, 1987; Rosenzweig, 1984; Renner & Renner, 1993) Parental & Peer Influences • Shared environmental influences from womb onward typically accounts for less than 10% of children’s differences (Plomin, 2018b) • Research implications suggest that parents should be given less credit who who kids turn out to be and less blame for kids who don’t turn out well (Scarr, 1993) • Peer influences may be stronger • Often attempt to make our behavior reflect those of peer influences and this is conserved across the child and adulthood • Example: Preschoolers who disdain foods will eat them if their peers like them; Teenagers more likely to smoke if peers model it (Blakemore, 2018; Harris, 1998; 2000) Cultural Influences • Variation of cultural norms change over time • Individualists: Independent sense of me • Collectivists: Sense of values and identity come from the group Gender Development • Categorization and classification • Birth-assigned determines sex • Mind determines gender • Cultural expectations, biology and experiences influence gender Nature influences of Gender • Prenatal sexual development • Father contributing X chromosome making female • Father contributing Y chromosome making male • Adolescent sexual development • Puberty influencing expression of male or female gender Nurture influences of Gender • Gender roles: Social expectations that guide people’s behavior as men and women • Subsumes how others expect us to think, feel, and act • Gender identity: Personal sense of being male or female (if one considers themselves binary) and sense of not identifying as either male or female (as one who considers themselves non-binary) • Cisgender: Those who identify their gender identity from the sex assigned at birth • Transgender: Those who identify their gender identity that differs from the birth-assigned sex