lecture4 - BioNB 221: Lecture 4 Sept. 5, 2008 Lecture 4:...

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BioNB 221: Lecture 4 Sept. 5, 2008 Page 1 Lecture 4: Genes & Behavior Janet Shellman Sherman Darwin’s theory of Natural Selection spawned fruitful discussion and investigation into human evolution. Sir Francis Galton applied Darwin’s theory to the study of eugenics, i.e. the acquisition of good traits through good breeding. As a result of Galton’s efforts the first TWIN studies were launched to determine whether human intelligence was inherited. Figure 1 shows results of an early study comparing grade similarity in monozygotic twins (MZ, from the same ova) versus dizygotic twins (DZ, from two ova developing simultaneously). Twin studies today have taken their cues from these early works. Scientists have implemented more careful controls to understand the genetic components revealed by MZ versus DZ twins. But the early studies of human trait inheritance had an unforeseen impact on public policy and politics. Sterilization programs (e.g., in US and Germany) and euthanasia programs (in Germany) were enacted to prevent feeble- minded and defective humans from becoming “drains” on society. A backlash occurred and some scientists focused on NURTURE, i.e., the environmental influences on behavior, while others re-focused on NATURE of non-humans, i.e. the genetical influences on behavior. Continuing investigation of genes and behavior became the domain of Ethology, i.e., the study of animals and humans in their natural environment. Ethological studies emphasized the genetically hard-wired repertoires. Still with us today are ethological terms like “innate”, “imprinting”, “stereotype”, and “fix-action patterns”. Eventually, nature –nurture debate lost steam. As more evidence of animal behavior was gathered, patterns of variation in traits suggested to many scientists that both nature and nurture influence behavior, and that any behavior can be analyzed at multiple levels of analysis. Ernst Mayr in
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lecture4 - BioNB 221: Lecture 4 Sept. 5, 2008 Lecture 4:...

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