The New Science of Evolutionary PsychologyChapter 2

Three Theories for The Origins of Adaptations•Creationism•Seeding theory•Evolution by natural selection

•Which of the theories is scientific and why?

The Three Products of Evolution•Adaptations•By-products•Noise

What is an Adaptation?•An inherited and reliably developing

characteristic that came into to existence through natural selection because it helped to solve a problem of survival or reproduction during the period of its evolution

•Must show evidence of special design•Must show evidence it improves fitness

The Environment of Evolutionary Adaptedness (EEA)•The adaptive problems or selection forces

that were responsible for shaping the adaptation over deep evolutionary time

•Not a time period, but a set of circumstances

•Each adaptation has its own EEA

Byproducts•Characteristics that do not solve design

problems and do not have functional design

•Come along with adaptations

Noise•Random effects•May harm the organism or be neutral

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The female orgasm: Adaptation, by-product, or noise?

Levels of Evolutionary AnalysisGeneral Evolutionary Theory (Darwin)

Middle Level Theories: Parental Investment

Theory (Trivers) Specific Evolutionary Hypotheses: In species

where males contribute resources to offspring, females will seek males who are willing and able to do so Specific Predictions Based on Hypothesis: Women

prefer men who show generosity during courtship

Strategies for Generating and Testing Hypotheses Theory Driven

Parental Investment Theory

Develop and Test Hypothesis: collect observations of women’s responses to personal ads that vary with regard to stated income

Observation Driven

Develop and Test Hypothesis: collect observations of women’s responses to personal ads that vary with regard to stated income

Observation: women seem to prefer men who have higher incomes

Human Nature•All species have a nature that evolved

through natural selection•All psychological theories are

evolutionary- all contain premises about human nature

•The human mind has evolved psychological mechanisms to solve adaptive problems

What is a Mechanism?•Example: Callous producing mechanism

▫Physical processes that cause toughening of the skin in response to specific environmental inputs

•Solves a specific problem•Is a universal mechanism but the output

will vary based on experience

Evolved Psychological Mechanisms: Definition•Exists because it evolved as an adaptation•Designed to process specific, limited input•Input has information value to the

organism about what adaptive problem it is facing

•Input takes form of decision rules (if-then)•Output: physiological response,

communication to other mechanisms, or overt behavior

•Output of mechanism is directed at solving a particular adaptive problem

Properties of Evolved Psychological Mechanisms•The mind is “carved at its joints” based on

function, although functions are coordinated

•Mechanisms are problem- specific and numerous

•Mechanisms are not rigid instincts but allow behavioral flexibility ▫Are activated by specific environmental

inputs▫Involve decision rules that permit multiple

options

Evolution and Culture•Evolution and learning are not opposites•Learning and culture are descriptions for

how environmental inputs interacts with psychological mechanisms

•Culture is a description that requires explanation- it is not an explanation by itself

Culture

Methods for Testing Hypotheses•Comparing species•Comparing males and females•Comparing individuals within species•Comparing individual across contexts•Experimental methods

Data Sources for Testing Hypotheses•Archaeological records•Data from hunter gatherer societies•Observations•Self-reports•Life history data and public records•Human products

* Multiple data sources allow evidence to converge

Identifying Adaptive Problems

Guideline 1: Modern Evolutionary Theory

•Problems of survival and growth•Problems of mating•Problems of parenting•Problems of assisting genetic relatives

Guideline 2: Knowledge of Universal Human Structures•Identifying common features of human

experience provides a starting place for likely adaptive problems (e.g. Brown’s Human Universals) ▫Social hierarchies▫Giving birth in presence of others

Guideline 3: Traditional Societies•Hunter-gatherer groups more closely

resemble the conditions under which humans evolved

•Humans were hunter-gatherers for 99% of our history

Guideline 4: Paleoarchaeology and Paleoanthropology•Analysis of fossils and tools allows a

window into adaptive problems that our ancestors faced

Guideline 5: Current Psychological Mechanisms•Fear of snakes•Taste aversions•Sexual jealousy

Guideline 6: Task Analysis•Analyze an observation into the various

behavioral and cognitive tasks necessary for it to occur

•Observation: humans generally avoid sexual contact with closely related kin