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Origins of Variation

  • Variation in biological traits arises from genetic and epigenetic factors, as well as cultural influences.

Epigenetics & Culture

Learning Objectives

  • Mechanisms of Epigenetic Marking: Understand DNA methylation, histone modification, and non-coding RNA regulation.

  • Inheritance of Acquired Traits: Explore evidence for epigenetic inheritance and its role in adaptive variation, such as defense mechanisms in plants.

  • Cultural Transmission: Describe how cultural behaviors influence adaptive variation in social animals, illustrated by food choices in monkeys.

Darwin's Perspectives

Quotes from Charles Darwin

  • "Nothing can be effected unless favourable variations occur" (The Origin of Species, 1859).

  • "Use in our domestic animals strengthens and enlarges certain parts, and disuse diminishes them; such variations are inherited" (The Origin of Species, 1859).

Inheritance of Acquired Characters

Conrad Waddington's Experiments (1950s)

  • Examined inheritance of acquired traits through genetic assimilation.

  • Notable study: Heat-stressed flies exhibiting lost wing veins were selected, and offspring displayed the trait without heat stress.

  • Holeski et al. (2012): Investigated parental environmental cues leading to hormonal defense induction in progeny seeds.

Definitions of Epigenetics

  • Non-genetic inheritance: Inheritance channels not represented in DNA sequences, including culture and epigenetic factors.

  • Epigenetics: Heritable changes in gene expression through DNA modifications or molecular interactions, independent of genetic code.

Mechanisms of Epigenetic Marking

  1. DNA Methylation: Addition of a methyl group, altering gene expression and can be inherited.

  2. Histone Modification: Modifications to histones modifying gene expression impact, leading to complex influences.

  3. Non-coding RNA Regulation: Involves various RNAs that influence gene activity and are heritable.

Epigenetic Variation

Arabidopsis Experiment

  • Observed that hybrid offspring with differing methylation exhibit varied phenotypes despite identical DNA.

Darwin’s Finches

  • Explored if epigenetic variation offers a better explanation for species variation than genetic differences.

Methylated Monster

  • Peloric toadflax presents a case of epigenetic variation with a silent gene influencing morphology.

Cultural Transmission

  • Cultural traits provide an alternative inheritance system, separate from genetic factors, especially in social animals.

  • Tradition: Phenomena of social learning persisting through generations contribute to a community's culture.

Research on Animal Culture

  • Studies indicate culture is present in species such as monkeys and whales, demonstrating social learning and adaptive traditions.

Exemplar Studies

  • Observed food preferences in social settings and the influence of peer behavior on feeding choices within primate populations.

Gene-Culture Coevolution

  • Interplay between genetic evolution and cultural practices demonstrated in human societies.

Origins of Heritable Variation

  • Factors:

    • Genetic Mutation: Undirected changes in DNA sequences.

    • Sexual Reproduction and HGT: Shuffle and transfer variants among populations.

    • Transposons: Move genetic material to new locations.

    • Mutualism: Organismic associations fostering heritable traits.

    • Epigenetics: Heritable marks through environmental interactions.

    • Culture: Culturally learned behaviors shaping traits over time.

Upcoming Discussion Points

  • Karl Ernst von Baer’s early studies and implications regarding embryonic development and classification.