Evolutionary Psychology Crash Course

Darwinian Theory

  • Darwin's Three Basic Statements:

    • Reproductive Capacity: Organisms have the potential to reproduce at an exponential rate.

      • Example: Two flies can multiply into 6 trillion in a year. Two elephants can produce 19 million offspring in 750 years. A single bacterium could reproduce into a mass covering the Earth in 52 hours.

      • Reality Check: These theoretical scenarios don't happen, because of constraints.

    • Constant Population Size: The number of individuals in a population remains relatively stable over time.

      • Example: A vole population contains 5-20 individuals in winter and 30-100 in summer.

    • Scarce Resources: Organisms compete for limited resources such as food, territory, and habitats.

    • Consequence: Competition for resources.

Additional Statements And Consequences

  • Individual Uniqueness: Each individual is unique and irrepeatable.

    • Breeders have long recognized this.

  • Heritability: Most individual differences are heritable.

    • Darwin hypothesized this, but didn't prove it.

    • Later discoveries: Mendel's genetics, Watson and Crick's DNA structure.

  • Consequences:

    • Differential Reproductive Success: Individuals have varying success in reproducing.

    • Gradual Change: Differences accumulate across generations, leading to gradual changes in the distribution of characteristics within the population - evolution.

Selection

  • Variety of Genes: A population possesses a variety and distribution of genes.

    • Example: g1 g1 g1 g1 g1 g1 g2 g2 g2 g3 g3 g4 g4

  • Phenotypes: Genes code for characteristics called phenotypes.

    • Example: f1 f1 f1 f1 f1 f1 f2 f2 f2 f3 f3 f4 f4

    • Phenotypes include structure, external traits, functions (e.g., metabolism), behavior, and mental processes.

  • Survival and Reproduction: Phenotypes can influence an organism's chances of survival and reproduction.

Phenotype Selection

  • Differential Chances: Phenotypes affect survival and reproduction.

  • Generation N: Example:

    • g1 g1 g1 g1 g1 g1 g2 g2 g2 g3 g3 g4 g4

    • f1 f1 f1 f1 f1 f1 f2 f2 f2 f3 f3 f4 f4

  • Selection Pressure: A circumstance (natural or sexual) that makes one phenotype disadvantageous while favoring another.

    • Example: f1 is disadvantageous, but f3 is favored.

    • Note: Phenotype is directly selected.

  • Generation N+1: Example:

    • g1 g1 g1 g1 g2 g2 g2 g3 g3 g3 g3 g4 g4

    • f1 f1 f1 f1 f2 f2 f2 f3 f3 f3 f3 f4 f4

  • Gene Distribution: Selection works on the phenotype but affects the distribution of gene variations.

  • Gradual Change: Evolution is a gradual change, but the speed varies.

Types of Selection

  • Natural Selection: Selection pressure comes from the environment.

    • It's interactive.

  • Sexual Selection: Selection pressure is generated by preferences of the other sex, in sexually reproducing species.

    • Can counter natural selection.

    • Handicap Principle: Example - peacock's tail or deer's antlers.

Design and Imperfection

  • Trial and Error: Evolution is a trial-and-error process, not a literal "design."

    • No

Some important concepts

Adaptation:

  • A structure (morphological, mental, or behavioral) serving a specific function, but not other functions (domain-specificity)

  • Cf. proximative and ultimative explanations

  • Increases reproductive fitness and chances of survival

  • An example: the peacock’s tail

  • Exaptation: An adaptation that had a different function before, but now has a new one, e.g. bird feathers: first function was heat regulation – later flight

  • Side-effect or by-product: Consequence of an adaptation but no function

  • Not everything is an adaptation!

Co-evolution

  • Two kinds of organisms evolve together through interaction

  • E.g. ‘arms race’ between predators and their prey; but peacock’s tail, too

Sexual selection

  • The choices/preferences of the other sex as selection pressure

The „Standard Social Science Model”

  • Human mind is „tabula rasa” or „blank slate”

  • The human mind is like a „general purpose computer”

  • Mechanisms(e.g.reasoning, learning) are independent of the content

    – This is wrong, as we have seen (Wason-selection task – and what else? Even animal cognition is domain-specific.)

  • Human concepts are arbitrary social constructions

  • Evolutionary psychologists:‘This is wrong’

    – EP: social construction is important, but subject to selection pressures

  • EP: psychology should be rooted in biology; – the „five principles” (Tooby & Cosmides, 1992)

Principle 1

  • The brain is a physical mechanism. It works like a computer, but its circuitry is ‘designed’ to conduct behavior that adapts to environmental circumstances

  • See also animal cognition

  • In humans: see mating strategies, parental behavior,

    groups (ingroup vs outgroup), dominance hierarchies

  • Even something as the concept of „justice” may have an evolutionary background

Principle 2

  • Neural circuitry was shaped by natural selection so that we are able to solve problems that repeatedly occurred in the evolutionary history of our species

  • The ‘right’ behavior (NOT morally, but from an adaptational point of view): adaptation, enhancement of prospects of survival (and propagation)

    – E.g. How about a pile of sh*t?
    – Well, flies like it! (Food & mating prospects)

  • A general purpose computer can be programmed to do anything – the mind can not

  • Adaptational problem:

    • –  Recurrent in the species’ history

    • –  Affects the reproductive success of individual organisms

    • –  Not everything is an adaptation

Principle 3

• Consciousness is just the ‘tip of the iceberg’

• Most problems require much more sophisticated solutions than we think

• E.g. vision
• Consciousness as the ‘CEO’ (cf. Bargh, 1996)

Principle 4

  • For the solution of different adaptational problems, different special-purpose neural circuits have evolved

  • There is no ‘universal tool’ – this is true to the mind as well

  • E.g. finding a mate vs finding food

  • Brain = a set of functionally integrated modules

  • Humans have a general-purpose intelligence as well, but this is much slower

  • Domain-specific mechanisms are quicker – E.g. learning in infancy (vision, language)
    – Intentionality

    – Of course, domain-specific knowledge can be acquired from the culture, too (e.g. chess)

  • Domain-specific modules of the mind

    • –  1) their complex structure serves the solution of a specific adaptational problem

    • –  2) present in every ‘normal’ human being

    • –  3) no effort of formal learning is needed for them

      to develop

    • –  4) we apply them unconsciously

    • –  5) they are different from general-purpose intelligence

Principle 5

• We live in a modern age but our minds are from the stone age

• Evolution: a LONG time
• The context of the development of the human

mind: stone age (hunter-gatherers)

• See e.g. human group sizes, objects of our fears