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The History of Behavior Genetics How nature affects our genetics and how our genetics change how we perceive and deal with our environment. Leaving evolutionary and entering biological genetics… evolutionary psychologists : universal human tendencies behavior geneticists : differences in one another What is the relationship? Sir Francis Galton Sir Francis Galton, inspired by his cousin Darwin's Origin of Species (1859), pioneered the field of behavioral genetics. Galton believed all human traits, including behavior, are solely determined by genes, without any contribution from the environment. Sir Francis Galton Founder of Eugenics This idea became the basis for eugenics, a term Galton coined in 1883 to describe the use of genetics for social planning. Galton, in other words, believed that selective "breeding" of the human species could guarantee that the "best" traits would remain in the human population while the "worst" traits could be eliminated. Sir Francis Galton Founder of Psychometrics Psychometrics is the field of study (connected to psychology and statistics) concerned with the measurement of "psychological" aspects of a person such as knowledge, skills, abilities, or personality. Critics, including "hard science" practitioners and social activists, have argued that such definition and quantification is impossibly difficult and that such measurements are very often misused. This is What can Happen When Bad People Hear Good Ideas Based on Galton's ideas, the eugenics movement built momentum in the United States, where between 1905 and 1933, several states based laws and legal decisions on eugenics theory, and the federal government heavily restricted immigration from Eastern and Southern Europe. The Johnson Act limited immigrants from each country according to their proportion in the U.S. population in 1890 — a time prior to the major waves of southern and eastern European immigration when the U.S. was decidedly more Anglo-Nordic in composition. This is What can Happen When Bad People Hear Good Ideas The goal was the production of a genetically "pure" American population. During this time in American history, criminals, people with low IQs and, in some cases, even women who had illegitimate children, were sterilized. This is What can Happen When Bad People Hear Good Ideas During its time in power, the government of Nazi Germany staunchly supported and enforced the principles of eugenics. Eugenics-based legislation culminated in the "euthanasia" of the mentally retarded and the physically disabled, who, according to Nazi geneticists, would otherwise contaminate the German people with unfit genes. A Swing Back in the Other Direction It was not until the 1980s that the scientific community began to pay serious attention to behavioral genetics as a science. Using gene manipulation technologies which had been in the works since the late 1960s, geneticists could finally map the human genome itself. A Swing Back in the Other Direction Since the early ’80s, geneticists have identified genes for cystic fibrosis, muscular dystrophy, and Huntington's disease. The successes in identifying and mapping human disease genes have revitalized interest in identifying genetic factors underlying behavioral traits. Nature, Nurture and Human Diversity Behavior Geneticists study our differences and weigh the relative effects of heredity and environment. Differences Brain: Asymmetry of brain across genders Biology: May change during development Genes: Genetic anomalies may make us different Behaviour: speak different languages Similarities Genes: Same set of Chromosomes Biology: The organs and body function the same Brain: Same brain Architecture Behaviors: Speak language Genes: Our Code of Life In the nucleus of a cell chromosomes containing DNA (deoxyribonucleic acid) are situated. Segments within DNA constitute genes making proteins to determine our development. Genome Genome is the set of complete instructions for making an organism containing all the genes in that organism. Thus human genome makes us human and the genome for drosophila makes it a common house fly. The Two Main Tools of a Behavior Geneticist: The Goal: Behavior Geneticists must try to untangle the mystery between the influence of genetics (nature) and the environment (nurture). The Tools: Twin Studies Adoption Studies Types of Twins Identical twins Fraternal twins Same sex only Same or opposite sex (Identical Twins) Monozygotic twins develop when a single egg is fertilized by a single sperm and at some stage in the first two weeks the developing embryo splits in two, with the result that two, GENETICALLY IDENTICAL babies develop. (Fraternal Twins) Dizygotic twins occur when two separate eggs are fertilized by two different sperm. These two fertilized eggs then develop independently. Dizygotic twins share the same type of genetic relationship as non-twin siblings, hence the term fraternal. Two placental arrangements in identical twins Separated Twins A number of studies have looked at identical twins raised separately from birth or close there after and have found a number of similarities. Interests, Fears Brain Waves, Heart Rate Abilities, Attitudes Personality, Intelligence Brain Waves, Heart Rate Separated Twins Critics of separated twin studies note that such similarities can be found between strangers. However, researchers point out that differences between fraternal twins are greater than identical twins. Adoption Studies Opposed to twin studies, adoption studies suggest that adoptees (who may be biologically unrelated) tend to be different from their adoptive parents and siblings. Adoptive Studies Adoptive studies strongly point to the simple fact that biologically related children turn out to be different in a family. So investigators ask: Do siblings have differing experiences? Do siblings, despite sharing half of their genes, have different combinations of the other half genes? Ultimate question: Does parenting have an effect? Parenting Parenting does have an effect on biologically related and unrelated children. Faith, Politics Manners, Beliefs Attitudes, Values Parenting Influences Behavior Genetics Vocabulary Behavior Genetics study of the power and limits of genetic and environmental influences on behavior Environment every nongenetic influence, from prenatal nutrition to the people and things around us Behavior Genetics Vocabulary Temperament a person’s characteristic emotional reactivity and intensity Heritability the proportion of variation among individuals that we can attribute to genes may vary, depending on the range of populations and environments studied Group Differences If genetic influences help explain individual diversity in traits, can the same be said about group differences? Not necessarily. Individual differences in weight and height are heritable and yet nutritional influences have made westerners heavier and taller than their ancestors a century ago. Nature and Nurture Some human traits are fixed, like having two eyes, most psychological traits are liable to change with environmental experience. So genes provide choices to the organism to change its form or traits when environmental variables change. Therefore genes are pliable or self‐regulating. Gene-Environment Interaction Genes can influence traits which affect responses, and environment can affect gene activity. A genetic predisposition that makes a child restless and hyperactive, evokes angry responses from his parents. A stressful environment can trigger genes to manufacture neurotransmitters leading to depression. Molecular Genetics: Promises and Perils Molecular geneticists are trying to identify genes that put people at risk for disorders. With this kind of knowledge parents can decide to abort pregnancies where fetuses are suspected of having such disorders .But this opens up a real concern about ethical issues involving such choices.