 We contain messages from our parents on our chromosomes  Chromosome- Threadlike strands of DNA molecules that carry genetic information ◦ Each cell contains 23 pairs of chromosomes ◦ One chromosome comes from each parent

 Parents can produce an outrageous variety of combinations of chromosomes  Overlap of chromosomes explains similarities to parents ◦ Class examples

 1.) Family Studies  2.) Twin Studies  3.) Adoption Studies

 Examine blood relatives ◦ Look for resemblance on specific traits ◦ Expect greater similarity if heredity effects traits  Schizophrenia studies are an example of this ◦ 9% of siblings of schizophrenic patients show symptoms  What is a major problem with these studies?

 These studies compare both identical and fraternal twins on trait similarity  Identical Twins- Emerge when a single egg splits ◦ Exact same genetic blueprint  Fraternal Twins- 2 separate eggs are fertilized simultaneous ◦ Average of 50% gene overlap  What do results suggest?

 These studies examine the resemblance between adopted children and both their biological and adoptive parents  More similarity to biological parents= heredity  More similarity to adoptive parents = environment  What do results show?

 Heredity and Experience have a joint influence  Interactive Effects- Both heredity and environment seem to play off one another ◦ Schizophrenia example

 To review, what does evolutionary psychology say about behavior?

 Natural Selection- Heritable characteristics that provide a survival or reproductive advantage are more likely to be passed to subsequent generations ◦ These genes are thus selected over time

 Include adaptations:  Adaptation- An inherited characteristic that increased in a population (through natural selection) because it helped solve problem of survival or reproduction during time it emerged ◦ Ex.) Human preference for fatty food

 Organisms are born with behavioral adaptations for both survival and reproduction  Examples of natural behaviors organisms do to survive: ◦ Human fear of heights, snakes…etc

 Examples of behavioral adaptations designed to improve organisms chance of reproductive survival: ◦ In many species, females demand material goods and service from males in return for copulation opportunities ◦ Black-tipped hangingflies insist on gift of food before they mate  They even tie the length of copulation to the size of the gift. Anyone notice any parallels to modern society?