Genetics, Evolution, and Behavior

Brain Size and Complexity

  • Bigger brain doesn't necessarily mean smarter.
  • Complexity is determined by factors beyond just size.
    • Capybara: Simpler brain structure (rodent).
    • Rhesus Macaque: Larger, more complex (old world monkey).
    • Human: Large with many folds, increasing surface area.
    • Gorilla: Great ape, but less complex brain than humans.
    • African Bush Elephant: Large brain but fewer neurons than humans.
  • Neuron count:
    • Elephant: 5,590,000,0005,590,000,000
    • Human: 16,300,000,00016,300,000,000

Learning Lab 1 Recap: Operational Definitions

  • Daffy Duck aggression video: Varied interpretations of aggression.
  • Conceptual vs. Operational Definition
    • Conceptual idea of a construct (e.g., aggression).
    • Specific measurement for an experiment (e.g., verbal/physical aggression).
  • Key Elements of a good Operational Definition:
    • Specific: Measurable (e.g., IQ test score instead of "intelligence").
    • Valid: Measures what it intends to measure.
    • Measurable: Provides a way to quantify data.

Chromosomes and Genes: Basic Genetics

  • Ancient Greece: Hippocrates' early ideas about semen containing a design for offspring.
  • Gregor Mendel: Discovered dominant and recessive genes through pea plant experiments.
    • Mendel's work was contemporary to Darwin, but Darwin was likely unaware of Mendel's findings.
  • Genotype vs. Phenotype
    • Genotype: Genetic makeup present from conception (can be affected by epigenome).
    • Phenotype: Observable characteristics influenced by genes and environment.
  • Chromosomes and DNA
    • Chromosomes: Tightly packed DNA molecules.
    • DNA: Carries genes.
    • Inheritance: 50% of genetic material from each parent.
    • Humans: 46 chromosomes in 23 pairs.

Mendel's Particulate Nature of Inheritance

  • Dominant and Recessive Genes
    • Example: Brown eyes (dominant) vs. blue eyes (recessive).
  • Allele Representation:
    • B: Dominant brown-eyed allele.
    • b: Recessive blue-eyed allele.
  • Heterozygous vs. Homozygous Inheritance:
    • Homozygous (BB): Only brown-eyed genes.
    • Heterozygous (Bb): Brown-eyed (dominant), but carries blue-eyed allele.
  • Probability of Inheritance
    • 75% chance of brown eyes, 25% chance of blue eyes from heterozygous parents.
  • Relationship to Parents
    • 50% chance of sharing a particular gene with a parent (Hamilton's r = 0.5).
    • Grandparent/Grandchild: r = 0.25.

Polygenic Transmission

  • Polygenic Traits: Multiple genes combine to influence a single trait.
    • Examples: Hair color, height, skin color, blood pressure, intelligence.
  • Race as a Social Construct
    • Human DNA: 99.9% identical across races.
    • Differences are related to few genes (e.g., melatonin).

Epigenetics

  • Epigenome: Affected by environment, influences gene expression.
  • Identical Twins: Identical genomes, but differences arise due to environmental factors.
    • Examples: Sun exposure, diet, drug use.
  • Mechanisms:
    • Genes being turned on/off or up/down by environmental factors.
  • Intergenerational Impact:
    • Epigenetic changes can survive meiosis and affect future generations.
  • Definition:
    • Lasting changes in gene function caused by external factors without changing the DNA sequence.

Nature vs. Nurture

  • Classic Debate: Genetics (nature) vs. environment (nurture).
  • Intelligence: Historically a significant point of contention.
  • Ideal Experiment: Identical twins raised apart.
  • Minnesota Twin Studies: Ongoing research since the 1970s.

The Jim Twins: A Case Study

  • Jim Lewis and Jim Springer: Identical twins separated at birth.
  • Astonishing Coincidences:
    • First wives named Linda, second named Betty.
    • One married to Sandy.
    • Both named their first son James Allen.
    • Shared interest in woodworking.
    • Favorite beer: Miller Lite.
    • Smoked Salem cigarettes.
    • Deputy sheriffs.
    • Drove Chevrolets.
  • Psychological Testing:
    • Strikingly similar IQ and personality profiles.
    • Shared habits like nail-biting.
  • Genetic Influence: Mental abilities, personality, vocational interest.
  • Identical Twins: Not carbon copies, but variations on a theme.

Silver Fox Experiment in Russia

  • Stalin Era: Scientist breeding tame silver foxes.
  • Selective Breeding: Tamer foxes bred with other tame foxes.
  • Physical Changes in Foxes:
    • White patches.
    • Curly tails.
    • Floppy ears.
    • Barking (uncommon in wild canines).
    • Females cycling twice a year.
  • Domestication Hypothesis of Dogs
    • Tamer wolves near human settlements got food scraps.

Basics of Evolution and Natural Selection

  • Darwin Quote: "It is not the strongest of the species that survives, nor the most intelligent that survives. It is the one that is most adaptable to change."
  • Darwin's Background:
    • Born same day as Abraham Lincoln.
    • Wealthy family, allowing him to be a "gentleman explorer".
    • Father was a physician who criticized Darwin's lack of focus.
    • Voyage on the Beagle as a naturalist.
  • Darwin's Influences:
    • Grandfather: Erasmus Darwin (speculated about evolution).
    • Cousin: Francis Galton (invented correlation, regression, and contributed to eugenics).
  • Alfred Russell Wallace: Came up with the same basic theory of evolution.
    • Darwin shared credit, presenting both papers to the academy.

Darwin's Voyage and Observations

  • The Voyage on the Beagle: Worldwide trip, including the Galapagos Islands.
  • Three Problems Darwin identified:
    • Species Change Over Time: Challenged the belief in unchanging species.
    • Fossil Evidence: Showed extinct species related to current ones.
    • Special Traits: Species had traits finely tuned for their environment.
  • Archaeopteryx: Fossil linking dinosaurs and birds.
  • Linnaean Taxonomy: System for categorizing living things.

The Origin of Species and Natural Selection

  • Publication: 1859, describing descent with modification and natural selection.
  • Evolution vs. Natural Selection
    • Evolution: Change in gene frequency over time.
    • Natural Selection: Mechanism through which evolution happens.
    • Other mechanisms: Genetic drift, gene flow, mutation.
  • Mutation
    • Random mutation in a gene produces a new different trait.
    • If that trait is adaptive, it gets selected for
  • Survival of the Fittest: Phrase Darwin disliked, coined by Herbert Spencer but Darwin was pushed to use it.
  • Overproduction Problem: More individuals born than survive to reproduce. Thus, only the adapted survive.
  • Adaptations: Allow organisms to meet environmental challenges.

Evolutionary Psychology and Mate Selection

  • Evolutionary Psychology: Understands how behavioral abilities and tendencies have evolved and how they are adaptive.
  • Mating Systems: Mate preferences and parental investment shaped by selective pressures.
  • Parental Investment: Time, effort, and energy invested in offspring.
    • Humans: Relatively few offspring, high investment.
    • Females: More investment due to limited reproductive opportunities.
    • Evolution is not conscious.
  • Categories of Mating Systems
    • Monogamy: Two parents care for progeny; more common in birds.
    • Polygamy: One individual has multiple mates; typically polygyny (one male, many females).
    • Polyandry: One female, many males; rare, some bird species.
    • Promiscuity: (Polygynandry) - anyone can mate with anyone else; chimps are an example.

Prosocial Behaviors

  • Examples: Helping, sharing, comforting, cooperating.
  • Cooperation: Individual helps another, gaining an advantage.
  • Altruism: Individual helps another, incurring a cost.
  • Mutualism: Behavior benefits both species.
  • Cooperation: individuals pulling on the strings together to get food.
  • Food Sharing: Vampire bats regurgitate blood to share (reciprocal altruism).
  • Offspring Care: Western bluebirds help raise subsequent generations.

Prosocial Behaviors in Humans and Animals

  • Human Altruism: Risking oneself for strangers.
  • Belding's Ground Squirrels: Sentinel calls that increase personal risk.
  • Olive Baboons: Younger males act as wingmen for each other.
  • Hamilton's r
    • Amount of relatedness you share with an individual as an indicator of how much an individual will help
  • Heritability
    • Amount of variation in a characteristic within a population that can be attributed to genetic differences
    • IQ. Between 57−7357-73% of your IQ score is accounted for by your genetics

Cost-Benefit Analysis of Behaviors

  • Benefit to Helper and Helpy: Cooperation (selected for).
  • Benefit to Helpy, No Benefit to Helper: Selfishness.
  • Cost to Helper: Altruism.
  • Negative for Both Parties: Spite.
  • Dictator Game: Rejecting offers of less than 20% to punish the other individual.

Social Darwinism and the Ethical Considerations of Evolutionary Psychology

  • Genetic Determinism:
    • Genes are responsible for who we are.
    • Some genetics are just superior to others (Eugenics Movement, which is not a good idea).
  • Cultural Determinism: Absolutely everything is learned.
  • Naturalistic Fallacy:
    • What is natural is better.
  • Social Darwinism
    • People at the top of the social ladder are the most fit.
  • Evolution is not purposeful/has a plan.
  • Evolution is not directional humans are not more evolved than other species.