Behavior Genetics

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Behavior Genetics

• Differences between people due to genetics

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GENES

• Are DNA
• Transcribed into mRNA
• Produces amino acids

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Alleles

• Actual form of the gene
• Dominant and recessive forms
• Homozygous and heterozygous
• Haploid and Diploid

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Mendels finding

• Grow yellow or green peas
• YY crossed with yy
• All yellow, Yy
• Next generation YY, Yy, Yy, and yy

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Conclusions from Mendel

• Inheritance of each trait is determined by
  units that are passed on (called genes)
• One unit is inherited from each parent
• Different genotypes can produce the same
  phenotype
• Genes are discrete
• Trait may not show-up in an individual, but it
  still is passed on
• Single gene effects vs. polygentic effects

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Heritability

• Variance due to genetics divided by total
  variance
• Vt Ve Vg (Ve X Vg)
• Genetically determined vs. Heritable

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Chromosomes

• XX female, XY male
• 23 pairs in total
• Locus of a gene (Allele)
• Meiosis (reproduction) and mitosis (duplication)

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Pleitropic effects of Genes

• Different effects at different times
• Testosterone

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Methods of Behavior Genetics

• Cross fostering
• Artificial selection
• Twin studies and degree of relatedness
• Pedigree analysis

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Polar bears may have accidental cross-fostering
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IQ correlations

• Monozygotic raised together .82
• Dizygotic raised together .62
• Siblings raised together .41
• Siblings raised apart .24

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Milestones in the Origins of Modern Humans
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Origins of Modern Humans

• Homo Erectus
• Migrated from Africa to Asia (1.8 MYA)

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Increases in brain size during evolution
modern human brain size 1350 ccs
ardipithecus brain size 300 ccs
Australopithe-cus brain size 310-530 ccs
homo habilis brain size 580-752 ccs
homo erectus brain size 775-1225 ccs
Neandertal brain size 1200-1450 ccs
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Becoming Humans

• 6 mya first hominids
• 150,000 years ago homosapiens
• Neanderthal extinct 30,000 years ago
• Big brains 50,000 years ago
• Domestication of plants and animals 8,000 years
  ago

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Rise of Western Culture

• Fertile Crescent in Iran, domestication of plants
  and animals
• West to east spread
• Specialized labor
• Governments formed
• Technology developed

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Domination of the World

• Ships
• Guns and Steel
• Horses
• Diseases

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The Selfish Gene

• Richard Dawkins
• Replicator and vehicle
• Genes are immortal
• Bodies are mortal

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Inclusive Fitness Revolution

• What would you do if you were a gene?
• Ensure the survival of your vehicle (body)
• Making copies of yourself influence your
  vehicle to reproduce (find fertile mates, etc.)
• Aid in the survival and reproduction of other
  vehicles that contain copies of you (help
  genetic relatives)

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Group Selection

• Wynne-Edwards (1962)
• Explained apparent altruism
• Cant work because a non-altruist would be more
  successful than the altruist

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Inclusive Fitness

• Coefficient of relatedness, r
• Altruism and kin selection
• Reciprocal altruism?