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To what extent is our behaviour determined by genetic inheritance? -…
To what extent is our behaviour determined by genetic inheritance?
Key Terms & Definitions
Genes
DNA segments carrying genetic information
Influences traits and behaviours
Chromosomes
Structures containing DNA molecules
Genotype vs Phenotype
Genotype: Genetic code inherited from parents
Phenotype: Observable traits influenced by genotype and environment
Behavioural Genetics
Field examining genetic and environmental influences on behaviour
Heritability
Statistic estimating the proportion of behavioural variance due to genetic factors
Core Concepts & Theories
Twin Studies
Comparing monozygotic (MZ, identical) and dizygotic (DZ, fraternal) twins
MZ share 100% genes; DZ share approximately 50%
Reveals genetic influence by examining concordance rates
Family Studies
Genetic relatedness correlates with similarity in behaviour
Limitations: shared environment can confound results
Nature vs. Nurture Debate
Interaction between genetic inheritance (nature) and environmental factors (nurture)
Modern view: dynamic interplay rather than either/or
Adoption Studies
Examines resemblance between biological parents and adopted children
Separates genetic factors from environmental influence
Empirical Research & Evidence
Minnesota Twin Study (Bouchard et al. 1990)
Results: High similarity in IQ, personality traits (extroversion, openness), and social behaviours
Implication: Genetic factors strongly influence many aspects of behaviour
Investigated identical twins reared apart
Scarr and Weinberg (1976) - Adoption Studies
Results: Higher IQ correlations between adopted children and biological parents, yet also significant influence from adoptive family environments
Implication: Behaviour (e.g. intelligence) reflects both genetic and environmental influences
Studied adopted children in families with differing socioeconomic status (SES)
Caspi et al. (2003) – Gene-Environment Interaction
Examined 5-HTT serotonin transporter gene in depression
Findings: Individuals with short allele variant more likely to experience depression following stressful events
Implication: Genetics can predispose behaviour, but environment can modulate outcomes
Limitations & Critical Evaluation
Environmental and Cultural Factors
Cultural expectations and social norms significantly shape behaviour, beyond genetic predisposition
Environmental conditions can dramatically alter gene expression (epigenetics)
Methodological Limitations
Generalizability issues in twin/adoption studies due to selective sampling
Ethical constraints limit experiments on genetics and human behaviour
Reductionism
Critique: Oversimplifies complex behavioural processes to single genetic causes
Reality: Most behaviours influenced by multiple genes and environmental factors
Gene-Environment Interaction & Epigenetics
Epigenetics
Environmental factors (diet, stress, toxins) influencing gene expression without altering DNA sequences
Potential for transgenerational epigenetic inheritance
Case Studies (Epigenetic research)
Weaver et al. (2004): Maternal care in rats affects offspring stress responses through epigenetic mechanisms
Implication: Behavioural traits are influenced by genetic expression shaped by environment
Gene-Environment Interaction (GxE)
Genes set potential; environment modulates expression
Examples: nutrition affecting height, trauma influencing mental health outcomes
Ethical, Social, & Future Considerations
Social Implications
How genetic research impacts educational policies, healthcare, and criminal justice
Debate on genetic screening and designer babies
Future Considerations
Can genetic editing (e.g., CRISPR-Cas9 technology) predictably alter behaviour?
Ethical limits to genetic modification for behavioural improvement
Long-term societal impact of understanding genetic influence on behaviour
Ethical Concerns
Privacy and consent issues regarding genetic data use
Genetic determinism and risk of stigmatization or discrimination
Conclusion
Balanced Conclusion
Genetic inheritance provides a foundational predisposition but does not rigidly determine behaviour
Behaviour results from complex, dynamic interaction between genetics and environment
Answer to the Core Question
Behaviour significantly influenced by genetic inheritance but continually shaped and modified by environmental experiences