Genetics and Evolution of Behavior

Mendelian Genetics

• Prior to Mendel, the understanding of heredity was like mixing two colors of paint.
• Mendel introduced the concept of genes as units of heredity that maintain their structural identity from one generation to another.
• Key terms: chromosomes, DNA, RNA, homozygous, heterozygous, dominant gene, recessive gene.

Sex-Linked and Sex-Limited Genes

• Sex-linked genes are located on the X and Y chromosomes (sex chromosomes in mammals).
• Autosomal genes are located on all other chromosomes.
• Sex-limited genes are active in both sexes but more prominent in one sex (e.g., chest hair in men, breast size in women).

Genetic Changes

• Mutation: a heritable change in the DNA molecule.
• Mutation can result in a gene coding for a protein with a different amino acid.
• Mutations can be harmful or harmless (e.g., boosting the immune system against a virus).
• Mutations can occur in embryos or during cell division.
• Duplication or deletion of a chromosome can occur during reproduction.

Epigenetics

• Changes in gene expression without altering the DNA sequence.
• Example: genes active in developing fetuses become less active after birth.
• Activation of genes involves loosening the grip of histones on DNA.
• Adding an acetyl group (COCH3) activates a gene, while removing it tightens the grip again.

Heritability

• When variation depends on genetic differences.
• Determining heritability: comparing monozygotic twins and dizygotic twins, or adopted children and their biological parents.

Environmental Modification

• High heritable traits can be modified by environmental interventions (e.g., phenylketonuria (PKU)).

How Genes Influence Behavior

• Genes can influence behavior by altering the environment (e.g., attractive genes influence strangers' reactions, which in turn affect personality).

The Evolution of Behavior

• Evolution: change over generations.
• Species evolve through genetic influences, mutations, and increased reproduction.
• Artificial selection: breeders choosing individuals with desired traits to produce the next generation.

Misunderstandings about Evolution

• Lamarck's theory: not supported, as using or not using a body part does not affect its size or shape in the next generation.
• Evolution is not slowing down or stopping due to modern medicine, as it is driven by reproduction, not survival.
• Evolution is not always an improvement, but rather an adaptation to increase fitness and pass on genes.

Evolutionary Psychology

• Studies how behavior evolves.
• Some behaviors may seem unnecessary but have evolutionary explanations (e.g., goose bumps, infant grasp).
• Altruistic behavior: can be selfish or selfless, with examples like family, kin selection, reciprocal altruism, and group selection.