Evolution, Genetics, and Behaviour: Foundations for Biological Psychology

Study Guide - Smart Notes

Tailored notes based on your materials, expanded with key definitions, examples, and context.

Evolutionary Foundations of Psychology

Empedocles’ Theory of Biology

Empedocles (495–435 BCE) proposed early ideas about the origins of biological diversity, suggesting that natural selection operated long before Darwin formalized the concept.

Natural Selection: Empedocles believed that only well-suited creatures survived and reproduced, while deformed or unsuited ones perished.
Chance and Utility: Useful features arose by chance, and those with advantageous traits survived.
Contrast with Aristotle and Plato: While Empedocles emphasized chance, Aristotle and Plato argued for purposeful design in nature.
Historical Significance: Empedocles’ ideas predate Darwin’s theory of natural selection by over two millennia.
Example: "Most of the parts of animals came to be by chance; and when those parts were useful, the creatures lucky enough to have them survived."

Charles Darwin and the Voyage of the Beagle

Charles Darwin’s observations during the voyage of the HMS Beagle laid the groundwork for the modern theory of evolution.

Voyage Details: The Beagle’s journey lasted five years, covering South America, the Galapagos Islands, Tahiti, New Zealand, and Australia.
Scientific Contributions: Darwin classified thousands of species, collecting evidence that challenged the Biblical account of creation.
Key Terms: Fitness, survival of the fittest, and adaptive features are central to Darwinian theory.
Limitations: Darwin lacked knowledge of genetics, which was later provided by Gregor Mendel’s work.
Major Works: Origin of Species (little on humans), Descent of Man (outlines human evolution).

Genetics and Behaviour

Nature vs. Nurture Debate

The nature vs. nurture debate explores the relative contributions of genetic inheritance and environmental factors to human development and behaviour.

Nature: Inborn biological endowment (genetics).
Nurture: Environmental conditions and experiences.
Historical Context: R. Mulcaster coined the terms in 1582; Galton popularized them in the context of intelligence and eugenics.
Behavioural Genetics: Studies the effects of genes on behaviour.

Structure and Composition of DNA

Genes, composed of DNA, serve as instructions for synthesizing proteins and enzymes, influencing both anatomy and brain function.

DNA: Composed of four bases: Adenine (A), Thymine (T), Guanine (G), Cytosine (C).
Genes: Affect behaviour through anatomical development and molecular processes (e.g., brain wiring).
Genetic Similarity: Humans share 99.9% of their genes with chimps, 90% with mice, 50% with bananas, and 35% with roundworms.

Genetic Relatedness and Twin Studies

Genetic similarity varies by relationship, and twin studies are crucial for disentangling genetic and environmental influences.

Relation	Genetic Similarity
Identical Twins	100%
Parent/Child, Siblings, Fraternal Twins	50%
Grandparent/Grandchild, Uncle/Nephew, Aunt/Niece	25%
First Cousins	12.5%
Second Cousins	6.25%

Identical Twins (Monozygotic): Single egg splits; share all genes.
Fraternal Twins (Dizygotic): Separate eggs; share about half their genes.

Genetics or Environment? Comparing Twin Correlations

Twin studies compare correlations between monozygotic (MZ) and dizygotic (DZ) twins to estimate genetic and environmental contributions.

	Genetics	Environment
Corr (MZ)	0.80	0.60
Corr (DZ)	0.43	0.61

Genetic Influence: If Corr (MZ) > Corr (DZ), genetics play a significant role.
Environmental Influence: If Corr (MZ) = Corr (DZ), environment is more influential.

Chromosomes and Genetic Variation

Chromosomes are structures within cells that contain thousands of genes. Humans have 23 pairs of chromosomes (22 autosomes and 1 pair of sex chromosomes).

Genetic Diversity: The combination of chromosomes from both parents results in possible genetic combinations for offspring.
Cloning: Humans do not naturally clone themselves due to sexual reproduction and genetic recombination.

Evolutionary Psychology

Definition and Key Concepts

Evolutionary psychology systematically studies the biological basis of social behaviour, focusing on how evolutionary processes shape the mind and behaviour.

Survival of the Fittest: Fitness refers to the ability to survive and reproduce, which can involve physical traits, strength, or aggression.
Behavioural Examples: Eating ripe fruit, caring for relatives, and cooperation are seen as adaptive behaviours.

Critical Assumptions of Evolutionary Psychology

Evolutionary psychology is based on several key assumptions about the mind and behaviour.

Mind is Programmed by Evolution: Many mental processes and behaviours are shaped by evolutionary pressures.
Cultural Universals: Researchers look for behaviours that are common across cultures.
Inclusive Fitness: Individuals tend to act in ways that promote the survival of their own genes, including helping relatives.

Malodorous Mates and Genetic Diversity

Preferences for mates may be influenced by genetic diversity, as offensive body odour can signal genetic similarity, reducing the likelihood of healthy offspring.

Genetic Similarity: Partners with similar genes may produce less genetically diverse (and potentially less healthy) children.
Evolutionary Advantage: Choosing mates with different genes can enhance offspring’s immune system.

Acts of Altruism

Altruistic behaviour, such as helping others, can be explained by evolutionary theories.

Kin Altruism: Helping relatives increases the survival of shared genes (nepotism).
Reciprocal Altruism: Helping non-relatives with the expectation of future reciprocation.
Example: Bees exhibit kin altruism by sacrificing themselves for the hive.

Interactionism: Nature and Nurture Combined

Interactionism: A Tidy Compromise

Interactionism recognizes that both genetic and environmental factors contribute to language, intelligence, personality, social psychology, and learning.

Domain	Nature	Nurture
Language	Critical periods, universal timeline	Learn specific languages
Intelligence/Personality	Twin/adoption studies	HeadStart, intervention
Social Psychology	Attitudes, death penalty	Attitudes, prejudice
Learning	Phobias, vomiting	Modeling, training

Interactionism and Phenylketonuria (PKU)

PKU is a genetic disorder that illustrates the interaction between genes and environment.

Genetic Basis: Absence or inactivity of a liver enzyme (converts phenylalanine to tyrosine).
Prevalence: Occurs in 1 per 20,000 live births.
Environmental Intervention: Early detection and dietary changes can prevent intellectual disability.
Example: Blood/urine tests in the first two weeks of life are used for diagnosis.

Additional info:

Suicide statistics by age and gender (Canada, 2003) are relevant to psychological research on stress, coping, and health, as well as social psychology.