Biology Chapter on Evolution and Behavior

Spontaneous Generation Hypothesis

• Disproven by Redi and Pasteur's experiments
• Redi observed maggots appearing only in uncovered jars of meat, indicating flies laid eggs.
• Pasteur demonstrated microbial growth in uncovered broth flasks, while covered flasks remained clear.

General Evolution Theory

• Organisms better adapted to their environment are more likely to survive and pass on advantageous traits.

Human Place in the Universe

• Understanding our place in the universe is humbling and freeing.
• Examples like instinct blindness highlight complex evolved behaviors.
• Our evolved color perception aids in identifying food.

Nature vs. Nurture

• Fallacy 1: Behavior is neither solely genetic nor solely environmental; it's an interaction.
• Fallacy 2: Evolutionary adaptations do not preclude change; we can adapt to changing environments.
• Fallacy 3: Evolutionary past does not dictate present behavior; we are plastic and flexible.

Social Psychology

• People tend to overestimate their own abilities relative to others (better than average effect).

Natural Selection Dating Methods & Systematics

• Before Darwin:
  • Jean-Baptiste Lamarck proposed species change, driven by a "natural tendency" and inheritance of acquired characteristics.
  • Georges Cuvier proposed catastrophism, explaining species extinction and replacement.
• Before Darwin (cont.):
  • Malthus noted populations grow faster than resources.
• Darwin:
  • Darwin's voyage on the Beagle, and observations of Galapagos finches suggested common ancestry.
  • Species struggle for resources, leading to the survival and reproduction of the best-suited individuals in a particular environment.
  • Gradual changes over many generations lead to complexity and efficiency.
• Darwin (cont):
  • The Origin of Species highlighted natural selection, abundance of heritable variation, and the struggle to survive.
• Mendel's Contributions:
  • Mendel's pea experiments showed traits are inherited in particulate units (genes).
  • Each parent contributes one gene copy.
  • Gene expression is influenced by both parental genes.

Dating Methods

• Principles:
  • Matter degrades over time; radioactive isotopes decay.
  • Layers of sediment represent time (e.g., volcanic activity).
• Methods:
  • Carbon-14: Used for materials up to ~50,000 years old.
  • Stratigraphic layers: Provides relative age based on geological layers.
  • Paleomagnetism: Uses Earth's magnetic field to determine age.
  • Radiometric dating: Measures decay of radioactive isotopes to determine age (e.g., potassium-argon).

Systematics (Phenetics and Cladistics)

• Phenetics: Uses anatomical similarities and adaptations.
• Cladistics: Based solely on relatedness.

Types of Selection

• Directional Selection: Favors extreme trait values in one direction.
• Stabilizing Selection: Favors intermediate trait values.
• Diversifying (Divergent) Selection: Favors extreme trait values in both directions.

Variation Maintenance

• Mutation-selection balance: Mutations introduce new variation; if selection is weak, variation is maintained.
• Frequency-dependent selection: Individual fitness depends on genotype frequency in the population.
• Heterozygote advantage: Heterozygous genotypes have higher fitness than homozygous genotypes.

Human Milieu and Inclusive Fitness

• Evolutionary Adaptations: Adaptations are traits favoured by natural selection, useful for a specific role.
• Adaptive Behavior: Functioning behaviour that increases reproductive success.
• EEA (Environment of Evolutionary Adaptedness): Pleistocene environment humans evolved in.

Bipedalism

• Humans are bipedal, more efficient than other primates.
• Adaptations contributing to bipedalism: broader hips, longer legs, curved lumbar, etc.
• Hypotheses for bipedalism: "man the hunter," "man the scavenger," "woman the gatherer".

Brain, Intelligence and Language

• Humans have larger brains than apes.
• Brain size increase ~3 million years ago.
• Hypotheses: Tool use / hunting, socialization, and complex interactions.
• Language development: lower larynx for sound production, hypoglossal nerve size, spinal cord width
• Hypotheses: language and tools, language and art, socialization.

Inclusive Fitness

• Inclusive fitness: overall reproductive success of relatives.
• Hamilton's rule (r*B>C) explains altruistic behavior related to kin.
• Kin selection related to altruism, and inclusive fitness.
• Humans give more to kin, evidence from Tsimane people of Bolivia and the "Cinderella effect."
• "Cinderella effect": stepparents > biological parents in terms of child abuse and injury rate.

Other Pressures (Death, Poison, Infection)

• Death: Evolution hasn't produced immortality due to pleiotropy (genes affect multiple traits).
• Infections & Poisons: Omnivorous animals more susceptible; sickness during pregnancy can result in dislike of certain foods/spices.

Studying Evolutionary Psychology

• Top-down vs. bottom-up: Top-down is theory-driven; bottom-up develops hypotheses from observation.
• Four Questions:
• Proximate mechanisms, development, function, evolutionary history).
• Criticisms: evolutionary psych isn't always experimental.
• Methods (comparing species; cross-cultural; Physiological)

Data Sources

• Experimental Observations: Strengths = highly controlled. Weaknesses = lack of setting.
• Archaeological Records: Strengths = snapshots; weakness = lack of soft tissue, incomplete.
• Hunter-gatherer societies: Strengths = insight into ancient lifestyles; Weakness = biased sample.