Genetics, Evolution, and Behavior

Brain Size and Complexity

• Bigger brain doesn't always mean smarter.
• Brain complexity is determined by folds and number of neurons not just size.
• Examples:
  • Capybara: Simple brain structure.
  • Rhesus Macaque: More complex brain.
  • Human: Many folds, large surface area, 16.3 billion neurons.
  • Gorilla: Fewer folds compared to humans.
  • African Bush Elephant: Large brain, but fewer neurons than humans (5.59 billion).

Learning Lab 1 Recap: Aggression

• Daffy Duck Video & Aggression Instances:
  • Varying counts of aggression due to open-ended criteria.
  • Aggression can be physical, verbal, or both.
• Operational Definition:
  • Conceptual idea vs. specific measurement.
  • Need to define aggression specifically (verbal, physical, target, duration).
• Three requirements for a good operational definition:
  • Specific: e.g., IQ score instead of just "intelligence".
  • Valid: Measures what it intends to measure.
  • Measurable: Must have a way to measure the construct.

Chromosomes and Genes

• Historical Context:
  • Hippocrates: Semen contains design for offspring.
  • Gregor Mendel: Discovered dominant and recessive genes via pea plants.
  • Mendel and Darwin: Contemporaries; Mendel aware of Darwin, but likely not vice versa.
• Genotype vs. Phenotype:
  • Genotype: Genetic makeup from conception, remains constant but epigenome can change.
  • Phenotype: Observable characteristics affected by genes and environment (epigenetics).
• Chromosomes and DNA:
  • Chromosomes: Tightly coiled DNA molecules.
  • DNA: Carries genes.
  • 50% of genetics from each parent.
  • 46 chromosomes in 23 pairs in each nucleus.
• Mendel's Particulate Nature of Inheritance:
  • Dominant and recessive genes.
  • Example: Brown eyes (dominant) vs. blue eyes (recessive).
  • Heterozygous brown-eyed parents (Bb) can have blue-eyed children (bb).
  • Probability of sharing a gene with a parent: 50% (0.5).
  • Hamilton's r: Correlation-like measure of relatedness (0 to 1).
    • Parent-child: $r = 0.5$
    • Grandparent-grandchild: $r = 0.25$
• Polygenic Transmission:
  • Polygenic traits: Multiple genes combine to influence a trait (e.g., hair color, height, skin color, blood pressure, intelligence).
  • Race: Social construct, not biologically meaningful; humans share 99.9% of DNA.
    • Differences related to few genes controlling melatonin in skin.

Epigenetics

• Epigenome affected by environment.
• Identical twins have identical genomes, but environment leads to differences over time.
  • Sun exposure, diet, smoking, exercise, etc.
• Genes can be turned on or off, up or down.
• Epigenetic changes survive meiosis and affect future generations.
• Lasting changes in gene function caused by external factors without changing the DNA sequence.

Nature vs. Nurture

• Nature: Genetic makeup and characteristics.
• Nurture: Environmental influences.
• Ideal experiment: Identical twins raised apart.
• Minnesota Twin Studies: Ongoing research since the 1970s.
• Jim Twins:
  • Separated at birth and reunited at age 39.
  • Shared similar experiences like wives' names (Linda and Betty), son's name (James Allen), favorite beer (Miller Lite), smoking habits (Salem cigarettes), and careers as deputy sheriffs.
• Twin studies show genetic influence on IQ, personality, and interests (40-50%).

Behavioral Genetics: Silver Foxes

• Scientist in Stalin-era Russia bred silver foxes for tameness to avoid political persecution.
• Breeding tamest foxes led to physical changes in few generations:
  • White patches, curly tails, floppy ears, barking.
• Supports domestication hypothesis of dogs: Less fearful wolves had better access to food scraps near humans.

Basics of Evolution

• "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.
• Darwin's background:
  • Born same day as Abraham Lincoln.
  • Wealthy family enabled him to be a gentleman explorer.
  • Father criticized him for lack of focus.
  • Voyage on the Beagle (as a naturalist).
  • Grandfather Erasmus Darwin speculated about evolution.
  • Cousin Francis Galton known for correlation/regression, eugenics.
• Alfred Russell Wallace independently developed same theory of evolution by natural selection.
• Darwin's voyage on the Beagle:
  • Collected specimens, identified problems with existing theories.
  • Three problems:
    • Species change over time (contradicted religious beliefs).
    • Categories for living things.
    • Traits with special functions finely tuned to environment.
• Linnaean Taxonomy: System of classifying living things (species, genus, family, etc.).
• Finches on Galapagos Islands:
  • Different beak shapes adapted to different food sources.
  • Big wide beak for nuts
  • Tiny fine beak for insects
• Darwin publishes "On the Origin of Species" in 1859.
  • Species are descended with modification and Natural selection is mechanism for the change.
• Evolution vs. Natural Selection:
  • Evolution: Change in gene frequency over time.
  • Natural selection: One Mechanism through which evolution happens. Characteristics increasing survival are preserved.
  • Other mechanisms: Genetic drift, gene flow, genetic mutation.
• Darwin recognized overproduction problem: more individuals born than survive.
• Adaptations: Products of natural selection, allowing organisms to meet environmental challenges.

Evolutionary Psychology

• Emerged as subfield in early 1990s.
• Seeks to understand evolution of behavioral abilities and tendencies.
• Helps understand mating systems and parental investment.
• Mating Systems:
  • Evolved patterns for choosing mates and rearing children.
  • Parental Investment: Time, effort, energy invested in offspring.
• Humans have relatively few offspring, leading to higher parental investment.
• More investment typically from mom than dad.
• Misunderstanding of evolution: It is not a conscious process.
• Parental investment related to mating system.

Mating Systems

• Monogamy: Two parents care for progeny, neither mates with others ex. Canada Geese
• Polygamy: One individual has multiple mate is most typically polygyny.
• Polygyny: One male mates with many females.
  • Sexual dimorphism: Males often bigger and flashier than females.
  • Sexual selection: Driven by female choice; males advertise.
  • Birds of Paradise example.
• Polyandry: One female mates with many males (rare).
  *Jacana example.
• Promiscuity (Polygynandry): Anyone can mate with anyone (e.g., chimps).

Human Mate Preferences

• Lucera study:
  • Women prefer men showing parental investment (interacting with child).
  • Men ignoring child rated lowest.
  • Men vacuuming might tap into idea of males as providers.
  • Men's attractiveness ratings same across conditions regardless of context.
• Evolutionary Underpinnings:
  • Humans as hunter-gatherers: Men hunt, women gather due to pregnancy/nursing.
  • Women dependent on men for resources.
  • Men emphasize youthful features and small hip-to-waist ratio in women.
  • Small waist indicates health, larger hips suggest safe childbirth.

Prosocial Behaviors

• Helping, sharing, comforting, cooperating.
• Cooperation: Helping another and gaining advantage.
• Altruism: Helping another at a cost to oneself.
• Mutualism: Behavior benefiting both species.
  • Sea turtle cleaned by angelfish.
• Information Sharing Ex. Meerkat sentinel
• Cooperation Ex. Two hyenas successfully pulling on a string.
• Food Sharing: Vampire bats regurgitate blood for others, but is not altruistic.
• Offspring Care: Western bluebirds help parents raise next generation in unfavorable conditions.
• Human Altruism: Complete strangers saving each other.
  • Often correlated with larger amygdala
• The Olive baboons also may help each other.
• Influences on Helping Behavior
  • Heredity. Hamilton's r, more closely related you are higher likelihood of help.
    *Studies have shown that genetics account for heredity can account for IQ scores. Studies show 57-73%.
  • In non-human animals more likely to help blood relatives.
• Behavior + net benefit.
  • Helper + helpy benefits (adapted/selected for).

Fallacies in Evolutionary Psychology

• Genetic Determinism: Genes solely responsible for who we are; tied to eugenics movement.
• Cultural Determinism: Everything is learned; genetics mean nothing.
• Naturalistic Fallacy: What is natural is better.
  • Essential oils vs. medication example.
  • Distorted findings used to justify harmful ideologies (e.g., Jeffrey Epstein funding evolutionary psychology).
• Social Darwinism: Free market capitalism; people at top are most fit.
  • Herbert Spencer coined term